Clarification on 15 Words Commonly Misused in English

1. Artist/Artiste
An Artist is a painter or somebody who draws or carves while an Artiste is a performer such as a dancer, an actor, or a singer.

2. Biannual/Biennial
Biannual means happening twice in a year while Biennial means an event taking place once every two years. Perennial means happening for very long period of time; happening again and again.

3. Luxurious/Luxuriant
Luxuriant is used to describe something rich, attractive, and beautiful while Luxurious is used to describe something that is very comfortable containing expensive and enjoyable things.

4. Born/Borne
Born normally comes before the preposition "of" e.g. Angela was born of Nigerian parents in Italy. Borne comes before the preposition "by". Borne is the last participle of bear while the past tense is bore e.g. Owen, the Italian football was borne by British mother.

5. Comprehensible/Comprehensive
Comprehensible is used to describe something that can be easily understood by an average reader e.g. His letter was quite Comprehensible. Comprehensive is used to describe what is complete and has all necessary information e.g. The report of the robbery crime was quite comprehensive. They are both adjective.

6. Client/Customer
A customer is one who buys something from a shop while a client is one who receives or gets services from a professional.

7. Elder/Senior/Younger/Junior
Elder and Younger are used within the family while Senior and Junior are used in schools or offices. Therefore, it is wrong to say: That boy is my senior brother. It should be: That boy is my elder brother.

8. Academic/Academia/Academician
An Academic is someone who teaches and does research in a university. That is, a lecturer. Many people mistake it for Academia which actually means a world of learning, teaching and research at a university. An Academician on the other hand is a member of an academy. An academy here means a type of official organization aimed at encouraging art, literature and science.

9. Talker/Speaker
A Talker is somebody who speaks well in a conversation e.g. Mary is a good talker, I enjoy her conversation. A Speaker on the other hand is used to talk about somebody who makes or delivers speeches in events e.g. Felicia Duncan is a good public speaker.

10. Altogether/All together
Altogether means "in total" or "completely" e.g. We are expecting twenty people altogether for the party. All together on the other hand means "all at once or all in one place" e.g. Pay me my money all together.

11. Beside/Apart from/Besides
Beside is a preposition used to show location e.g. I saw a rat beside your leg just now. Besides is used for making an extra comment to what has been said earlier e.g. I don't really love the girl. Besides she is ugly. It can also be used as a preposition meaning 'Apart from' and 'in addition' e.g. I do admire everything about you besides your laziness. Besides losing his parents, the poor boy is a school dropout.

12. Blind/Blindly
Blindly (adverb) means 'not being able to see what you are doing' or 'not thinking about something' e.g. The boy blindly went ahead to marry the evil girl. Blind (adverb) means not being able to see.

13. Cautious/Careful
Being Cautious means doing something slowly or after a lot of thought because of fear or nervousness while being Careful means doing something after a lot of thought but without fear or nervousness.

14. Close/Shut
Close and Shut could really means the same thing but note that when 'shut' is used, it involves more noise. Also, shut is more often used for containers such as boxes, suitcases, etc. Closed is used in front of a noun whereas, shut is not e.g. A closed door, but we cannot say: A shut door. Closed is also usually used with roads, airports, etc. e.g. The roads were closed because of the protest.

15. Distrust/Mistrust
Distrust is used if you are sure that someone is acting dishonestly or cannot be relied on while Mistrust is used if you express doubt and suspicious over a person's honesty. You are not quite sure.

Phrasal Verbs and Idiomatic Expressions

This article treats the meaning of idiomatic/figurative expressions as well as phrases realized by verbs with prepositions, known as phrasal verbs. Here are some phrasal verbs and idiomatic expression you should know.

1. Leave out – Omit
2. Drop off – decline gradually
3. Drop our – cease from participating
4. Run off (documents) – to copy from machine
5. Catch on – understand
6. Leave no stone unturned – do everything possible
7. Round off – to conclude
8. Round up – to arrest
9. Take in – to deceive
10. Take after – to resemble or look like
11. Fall through – to fail
12. Write off – to cancel
13. A leader in a newspaper – an editor
14. A dark horse – an unexpected winner
15. Small fry – an unimportant person
16. To be insolvent – to be bankrupt, to be cash-strapped
17. A plaintiff – a complainant
18. Perjury – to tell a lie in the court
19. To buckle down – to be hardworking or serious
20. Give in – to accept defeat
21. Jaundiced view – partial or bias view
22. Ostracize – to reject or send away
23. To cross the Rubicon – not going back on a decision
24. To leave for good – no coming back
25. White elephant – high cost, little value
26. To lead a dog's life – to live a life of misery, suffering
27. To be under a weather – to be ill
28. To be in the black – to have money in one's account
29. To make an appearance – to show up in a party for a short-time
30. To clear the air – to eliminate tension, confusion, anger
31. The bird has flown – a wanted person has escaped
32. To come off – to live above board, to be above suspicion
33. Laissez faire attitude – careless, care-free
34. To go with a chip on one's shoulder – to prepare for a quarrel
35. To have one's head in one's mouth – to be frightened or afraid
36. To break even – no loss no gain
37. To present a bold front – to be brave
38. To exhume a body – to dig up
39. To be gullible – to be easily deceived
40. To loathe – having a strong hatred, aversion, dislike towards somebody or something.

In the next article we are going to be writing about Words Commonly Misused.

Reporting Questions (Interrogative Sentence)

It has been statements we have been reporting all the while. When reporting a question (an interrogation sentence), the sentence begins with the pronoun or the name of the person asking the question e.g. we, she, Teddy, etc. Common verbs used in reporting questions include ask, inquire, query, wish to, know, demand, etc. Note that the verb (auxiliary verb) normally comes after the subject when reporting a question and the question mark is usually omitted.

Examples:
1. "Where is Owen going?" The woman asked. (Direct speech question)
The woman asked where Owen was going. (Indirect speech question)

2. "Are you coming now?" The principal asked me. (Direct speech question)
The principal asked me if I was coming then. (Indirect Speech question)

Note that reporting a polar question is different from reporting a non-polar question. A polar question is that which required "yes" or "no" answer while a non-polar question does not require "yes" or "no". It usually starts with "Wh" words. When reporting a polar question, we begin the report with "if" or "whether". Examples:

1. "Are you coming tomorrow?" The man asked me. (Dir. Sp. Polar question)
Indirect report: The man asked whether I was coming the next day.

2. "What is your name?" The principal inquired. (Dir. Sp. Non-polar question)
Indirect report: The principal inquired what his name was.

3. "Will I see you today?" The girl asked us. (Dir. Sp. Polar question)
Indirect report: The girl asked us if she would see us that day.

4. "Does the sun go round the earth?" The boy asked the professor. (Direct speech question)
Indirect report: The boy asked the professor whether the sun goes round the earth.

In the last example, nothing has changed in the report because the question is on a scientific issue and has a permanent truth.

Reporting Commands (Imperative Sentences)
Commands (imperative sentences) are structurally known to begin with verbs e.g. Get out, sit down, shut the door, shut up, etc.

When reporting a command, one common feature is that the verb in the direct speech form takes a "to-infinite". Reporting a piece of advice is usually the same as reporting commands. Commands are usually expressed with verbs such as commanded, instructed, ordered, demanded, advised, etc.

Examples:
1. "Get out now," the man ordered. (Direct speech command)

2. "Be frugal with your income these days of economic recession," the old man advised. (Direct speech advice)
Indirect report: The old man advised them (or him or her) to be frugal with their (or his or her) income those days of economic recession.

In the next article we are going to be writing about Phrasal Verbs and Idiomatic Expressions.

Direct and Indirect Speech

Direct Speech
In a direct speech, there are two clauses, the reporting clause and the actual clause. The reporting clause contains the words of the reporter while the actual clause contains the words of the actual speaker. In a direct speech, the exact words of the speaker are reported directly or verbatim. The actual words are put in quotation mark.

NOTE: Every word including punctuation marks such as commas is enclosed inside the quotation marks.

Example: "It is raining today," Peter said.
                    actual clause          reporting clause

Indirect Speech
The indirect speech on the other hand, involves reporting what the speaker has said with some modifications. This implies that the reporter does not use the exact words of the speaker, instead we have some alteration and because of this, quotation marks are not used. An indirect speech is also known as a reported speech. There are two clauses in an indirect speech. The two clauses are joined by 'that'. Sometimes 'that' is omitted.

Example: Peter said that it was raining that day.

The speech above is quite different from the earlier one we reported directly. Some parts of the speech have changed.

Parts of a reported speech that changed
– Pronouns
In a reported speech, the pronouns change i.e. all first person pronouns will change to their third person pronoun equivalent as seen below:

• I will change to He or She
• Me will change to Him or Her
• We will change to They
• Us will change to Them
• Our will change to Their
• Mine will change to His or Hers
• Ours will change to Theirs
• Myself will change to Himself or Herself
• Ourselves will change to Themselves

Note that when the reporter is the addressee, the pronoun "you" will change to "I/we" for subjective case or "me/us" for objective case. But if the reporter is not the addressee, "you" will change to "he/she/they" for subjective case or "him/her/them" for objective case. Examples:

1. "I will see you tomorrow ," the doctor told me. (Direct speech where the reporter is the addressee)
2. The doctor told me that he would see me the following day. (Indirect speech where the reporter is the addressee)
3. "You must be on your way now," the director told them that. (Direct speech where the reporter is not the addressee)
4. The director told them that they had to be on their way then. (Indirect speech where the reporter is the addressee)

– Verbs
In Reported Speech, verbs change in the other below:

• Present Tense verbs will change to Past Tense
• Past Tense will change to Past Perfect
• Present Progressive will change to Past Progressive
• Present Modal (shall, can, etc.) will change to Past Modal (should, could, etc.)
• Past Modal will remain as Past Modal

NOTE: Must and Ought to will change to Had to.

However, note that, the verbs will not change if the subject to be reported is a permanent truth. Instance include: Scientific statements, Geographical extrapolations, Statements from a Constitution or Charter, Statements from a Holy Book, etc. Also note that the verb in the reporter's clause determines the verb in the clause that is being reported. This implies that if the verb in the reporter's clause is present, the verb in the clause being reported will be present and if the verb is past then the other will also be past.

Examples:
1. "I am in the house," the man says (Direct Speech)
The man says he is in the house. (Indirect speech)

You will observe that the verb "says" in the direct speech is in the present tense and therefore, the verb "is" does not change to the past tense in the indirect speech.

2. "I am in the house," the man said. (Direct speech)
The man said he was in the house. (Indirect speech)

Unlike the first example, the verb in the reporter's clause is "said" which is a past tense verb therefore, the verb "am" changes to past tense "was".

In the next article we are going to be writing about Reporting Questions (Interrogative Sentence)

Disjunctive (Question Tag)

In a question tag there is usually a statement and a tag, the tag comes after the statement.

For example:  I saw Daniel, didn't I?
                          Statement        tag

Rules for Question Tag
– Rule one: If the statement is positive, the tag will be negative.

– Rule two: If the statement is negative, the tag will be positive. A negative statement or tag is identified by the present of the negators "not" and "never".

Examples:
1. I have not seen you before, Have I? (Negative statement-positive tag)
2. It is raining, isn't it? (Position statement-negative tag)

Note that the negative (not) in the tag is usually written with the verb in a contracted form e.g. (isn't)

– Rule Three: The statement is normally separated from the tag with a comma.

– Rule Four: The subject in the statement must be repeated in the tag e.g. He came yesterday, didn't he?

Note that if the subject is a noun, it must be changed to an appropriate pronoun in the tag. For instance, we cannot say: Julian is coming, isn't Julian? 'Julian' must be changed to its appropriate pronoun which is 'she'.

– Rule five: The verb in the statement must be repeated in the tag

Note: Only auxiliary verbs are applicable in question tag. This implies that if the verb in the statement is a lexical (main) verb, it must be changed to an auxiliary verb. The auxiliary verb applicable in replacing a lexical verb in the question tag is the auxiliary verb 'to-do'. This means that the lexical verb in the statement is changed to the verb 'to-do' in the tag. If the lexical verb is past tense, in the tag, it becomes did/didn't e.g. We stood up when the principal came in, didn't we?

If the lexical verb is present tense, in the tag, it becomes does/doesn't for singular subjects and do/don't for plural subjects. For instance, it is wrong to say: *"He came here, camen't he?* The verb 'came' is in past tense therefore it will be changed. Let us consider the examples below:

1. He came here, didn't he? (Past tense)
2. He comes here everyday, doesn't he? (Simple present singular verb)
3. They come here everyday, don't they? (Simple present plural verb)

– Rule Six: If the verb in the statement is the auxiliary should or must, it becomes need in the tag e.g. I should come tomorrow, needn't I? We must go, needn't we?

– Rule Seven: If the verb in the statement is a command verb, it is changed to will in the tag e.g. Get out, will you? Shut up, will you?

– Rule Eight: If the verb in the statement is "let" and the subject is "us" (let's), the verb in the the tag will be shall and the subject will be we e.g. Let us go now, shall we? Let's have a cup of coffee, shall we?

The rules we have discussed above are all based on Simple Sentences. The ruled to be discussed next are based on larger and non-simple sentence.

– Rule Nine: If the statement is a compound sentence, made up of two main clauses, the tag will be derived from the latter main clause. Examples:

1. Marina passed her exam and her father was very happy, wasn't he?
In the example above, there are two clauses joined by the coordinator 'and'. The tag is derived from the second clause 'her father was very happy'

2. You stole but your mother didn't beat you, did she?

– Rule Ten: If the statement is a complete sentence, the tag is derived from the main clause of the sentence. Remember that a complex sentence is made up of only one main/independent clause and the other(s), subordinate/dependent clause. Examples:

1. We stood up when the principal came in, didn't we?
The main clause here is 'We stood up'
2. When the principal came in, we stood up, didn't we?
3. We stood up when the Mrs Remix, the principal came in, even though Mr Akpan was angry, didn't we?

The tag is still derived from the main clause 'We stood up'. All other clauses are subordinate clauses. Note that the subordinate clauses in the examples above are adverbial clauses. It may also be a noun or an adverbial clause. Examples:

1. Marian doesn't know that you were joking, does she?
2. I said, "Kyle saw Daniel", didn't I?
3. It seems that the children are not paying attention, doesn't it?

In the next article we are going to be writing about Direct and Indirect Speech.

Miscellaneous Collocation

– Use of 'so' and 'that':
When 'so' is used in a sentence as an intensifier or degree adverb, not that a 'that' clause should follow e.g. The boy is so clever that he won all the prizes for his category. Avoid the use of 'so' if you do not use a 'that' clause.

– Use 'such' and 'that':
Just like 'so', when 'such' is used as an intensifier, it should be followed by a 'that' clause. The difference is that, an article 'a'/'an' should follow e.g. He is such a boy that everyone would love to see. Note that when an adjective and an article follow 'so', you should not use a 'that' clause e.g. it is wrong to say: He is so clever a boy that I would love to see him. It is better to just say: He is so clever a boy. If you must use a 'that' clause, then use 'such' instead of 'so' e.g. He is such a clever a boy that I would love to see him or He is such clever a boy that I would love to see him.

Two words that are also used as intensifier are 'too' and 'very'. However, note that when they are used, you must avoid the use of a 'that' clause e.g. it is wrong to say He is too/very clever that I would love to see him. Avoid the use of a 'that' clause with any of these intensifiers.

– Use of 'with a view to' and 'ing-verb':
When 'with a view to' is used in a sentence, note that the verb that should follow should be in a progressive (continuous) form e.g. I came here with a view to seeing the clever boy (not with a view to see).

– Use of 'look forward to' and 'ing-verb':
When 'look forward to' is used, the verb that should also follow should be in a progressive (continuous) form e.g. I look forward to seeing you next week (not look forward to see). We all look forward to enjoying ourselves at the party.

– Use of 'no sooner' and 'than':
When 'no sooner' is used in a clause, it should be followed by 'than' e.g. No sooner had I entered the house than the rain started.

– Use of 'scarcely'/'hardly' and 'when':
When 'scarcely' and 'hardly' are used in a clause, they should be followed by 'when' e.g. Scarcely had the semester started when the school was shut down. Hardly had I begun to speak when the bell rang. The concert had hardly started when the lights went off.

– Use of 'no choice' and 'but':
Note that when the phrase 'no choice' is used, you should not follow it with a clause beginning with 'than', but follow it with a clause that begins with 'but' e.g. The students have no choice but to pass. (Not than to pass).

In the next article we are going to write about Disjunctive (Question Tag).

Collocations in English

Collocation is a regular pattern in which words are formed. It is also described as the company that words keep.

Prepositional Collocations
Prepositional collocation involves the use of verbs with prepositions. It should be noted that certain verbs choose certain prepositions. This implies that the use of verbs with prepositions is not random.

1. Buckle down (not buckle up) meaning to concentrate on one's work.
2. Leave for (not leave to)
3. Link with (not link to)
4. Alongside (not alongside with)
5. Comprise (not comprise of)
6. Demand (not demand for)
7. Solicit (not solicit for)
8. Advocate (not advocate for)
9. Request (not request for)

Note that the verbs demand, solicit, advocate and request will only take the preposition 'for' if the speaker carries out the action on behalf of of somebody else. For instance: In the law court a lawyer can solicit or advocate for a client e.g. I, Barr Okon, am here to solicit for John. But when the speaker wants something for themselves, the preposition 'for' cannot be used. For instance: The protesters hit the streets to solicit their rights and request their salaries. They will also take "for" when used as nouns e.g. My demand for justice is firm; The request for our salary isn't a crime. Note that 'of' is used with 'comprise' when used in passive form and that case, it is used in the past form with the auxiliary verb 'to-be' (is, was, are, were, am, been and being) in front of it as in: 'be comprised of' e.g. The committee is comprised of eminent members of staff. When 'comprise' is used in an active form, it does not take 'of' e.g. The committee comprises eminent members of staff. (Not comprises of...)

10. Attached to (not attached with)
11. Interested in (not interest on)
12. In one's interest (not for one's interest)
13. Connect with (not connect to)
14. Believe in (not believe on)
15. Accordance with (not accordance to)
16. Congratulate on (not congratulate for)
17. In the meantime (not for the main time)
18. In black/white suit (not on black/white suit)
19. On campus (not in campus)
20. On bus (not in bus)
21. Round up ("round up" is usually misused to mean to end what one is doing. This is wrong! "round up" means to arrest while "round off" means to end what one is doing)
22. Agree with (somebody)
23. Agree to (something)
24. Angry with (somebody) (not angry at)
25. Result in (effect of something) e.g. the fuel subsidy removal resulted in a week-long strike.
26. Result from (the cause of something) e.g. the one week strike resulted from the removal of fuel subsidy.
27. In the long run (not on the long run)
28. Prefer to (not prefer than). E.g. it is wrong to say: I prefer rice than beans but you say I prefer rice to beans.
29. Share between/among: We use between when it is just two people that are involved e.g. Share the money between Jane and Juliet. On the other hand, we use among when more than two people are involved. E.g. Share the money among Jane, June and Juliet.
30. Deal in (trade) e.g. My mother deals in textile.
31. Deal on (treat or discuss an issue)
32. Travel abroad (not travel to abroad)
Note: It is wrong to put "to" when the name of the place is not mentioned. 'Abroad' is not a name of a country therefore it is wrong to say "travel to abroad" instead you say "travel abroad".
33. Eject (nor eject out): It is tautological to add " out" to eject.
34. Die of (a disease or sickness)
35. Die for (a cause, a belief or a struggle).

In the next article we are going to write about Miscellaneous Collocation.

10 Possessive case of Nouns

There are rules for forming the possessive case of nouns. Many non-native speakers of English encounter certain difficulties when they use nouns in the possessive case. The rules are discussed below:

1. Rule one:
To form a possessive case of a noun, you simply add apostrophe and 's' e.g. I saw the girl's uncle.

2. Rule two:
When the noun is an inanimate noun, avoid the use of apostrophe and 's' e.g. The table's leg is broken (informal). Instead you say: The leg of the table is broken.

3. Rule three:
If the noun is a plural ending with an 's', do not add 's' with the apostrophe sign, just put only the sign e.g. I saw the girls' father yesterday.

4. Rule four:
If the noun comes at the end of the sentence, still add the apostrophe and 's' e.g. That man is a friend of John's. (not that man is a friend of John).

5. Rule five:
In abstract nouns ending with 'ss' or 'ce', add only the apostrophe sign e.g. We should be happy to suffer for righteousness' sake. For silence' sake, the  boy walked away.

6. Rule six:
For names ending with 's' e.g. James, Jones, etc, the apostrophe sign and 's' should be put. For example: James's father, Jones's aunty, etc.

7. Rule seven:
If the word is a compound word, add apostrophe and 's' to the last word in the compound e.g., He sat on his class teacher's table. Note, if in a compound where we have two nouns whereby the first noun is qualifying the second, add the apostrophe and 's' to the first noun e.g. Grace Lawson collected the subject's prize.

8. Rule eight:
NOTE THESE!– women's liberation not 'women libration', women's studies not 'women studies', womenswear not 'women's wear', menswear not 'men's wear', women folk not women's folk'.

9. Rule nine:
Note these phrases: A week's time as in: I will see you in a week's time; a year's time, etc. Also note the use of else in a possessive form as in: Somebody else's book.

10. Rule ten:
Another expression that many speakers misuse is Students' Union. It's NOT *Student's Union* as often mistakenly used. It can also be used as Student Union. Finally, note the use of Parent-Teachers' Association (NOT Parents' Teachers' Association nor Parent Teachers' Association). A hyphen is put between Parent and Teacher and no apostrophe is used.

In the next article we are going to write about Collocations in English.

Singularity and plurality in Nouns

A singular noun has one number while a plural noun has more than one number. There are about six ways of forming plural nouns. These ways are discussed below.

– By adding "s" or "es" to the singular nouns
Examples:
Singular         Plural
Clock           clooks
Book            books
Train            trains
Table           tables
Cargo          cargoes
Mango         mangoes
Glass          glasses

Please note the following plural nouns ending with 'o':
Singular              Plural
Manifesto        manifestos
Motto                  mottos
Buffalo               buffalos
Commando     commandos
Piano                    pianos

Note: Some nouns that end with letters "O", " Ch", "S" etc. form their plural by the additional "es".

– By adding " en", or "ren" to the singular nouns
Singular         Plural
Child             children
Ox                    oxen
Brother         brethren

– By the changing of a vowel of the singular nouns
Singular         Plural
Tooth            teeth
Louse            lice
Mouse         mice
Man              men
Foot             feet
Goose         geese

– By changing letter "y" in the nouns to "ies"
Singular           Plural
Lady                ladies
Body               bodies
Fly.                    flies
Duty                duties
Army               armies
Reply               replies

– By changing "f" to "ves"
Singular          Plural
Thief              thieves  
Leaf                leaves
Life                  lives
Knife              knives
Wolf               wolves
Elf                   elves

Note: 'chief' does not become 'chieves'. You just simply add 's'- 'chiefs'.
'Handkerchief', 'dwarf', 'scarf', and 'hoof' can become plural either by adding 's' or 'ves'.

– By not changing the singular nouns (problematic nouns)
There are some nouns that don't take "s", " es", or anything to form their plural forms. Their spellings remain the same for both singular and plural forms. I call such nouns the problematic nouns. Examples:
Singular            Plural
Deer                  deer
*Fish                 fish(es)
Sheep               sheep
Furniture         furniture
Traffic               traffic
*Staff                  staff
Luggage           luggage (British)
Baggage           baggage (American)
*Property            property
Information      information
Equipment        equipment
*Damage            damage
Environment    environment

Note this: Bag and baggage (not bags and baggage nor bags and baggages)

Note that some of the words listed above can takes 's' in some specific cases.
For instance:
The members of clergy are respected.

* 'Fish' will be 'fishes' if we are referring to different species/types, such as tilapia fish, cat fish, electric fish, etc. For example: my mother bought ten tilapia fish from the market today; last week, she bought five fishes which included: tilapia, electric and cat.

*  'Clergy' will be clergies if we refer to different religions or denominations.

*  'Property' can be 'properties' if we mean 'characteristics' or 'features'. In legal parlance, we can also have properties.

*  'Damage' can be used in two forms. When we use it to mean demolition or destruction, note that the plural form does not take "es".
Example:
– The damages done by the flood are unspeakable. (Wrong)
– The damage done by the flood are unspeakable. (Correct)

The word will only take 'es':
  When used as third person singular verb such as:
– A baby damages fragile objects while growing up.

  When used to mean a certain amount of money ordered by a law court to be paid to somebody for an offence committed.
– Some damages were paid to the family of the victims.

Note that when we want to quantify some of the nouns in the table above, we use 'piece'. For instance:
– A piece of equipment
– Two pieces of equipment
– A piece of furniture
– Ten pieces of furniture.

We can also use 'member' for some of the nouns in the table above. For instance:
– The members of the clergy are respected.
– A member of staff.
– Five members of staff.

Note that we can also use 'staffers', but in American English. We can add 's' to 'staff' when we mean staff members of different groups or organizations. For instance:
– All the schools and their staffs were well represented at the meeting.
– All the law makers and their staffs are corrupt.

In the next article we are going to write about possessive case of Nouns.

Parts of speech: Nouns in English

There are about eight parts of speech in English. Some belong to the open class system and they include: nouns, pronouns, adjectives, adverbs and verbs, the other part of speech belong to the close class system and they include: prepositions, conjunctions and exclamations. Some other classes of part of speech include: articles, determiners, etc.

Noun may be defined as the name of a person, an animal, a place or thing. A noun could also be used to describe or refer to feelings, ideas, etc.

Classes of nouns
We have the following classes of nouns:
– Proper and Common Nouns
– Abstract and Concrete Nouns
– Countable and Uncountable Nouns
– Collective Nouns

1.  Proper Nouns
Proper Nouns are specific names of people, animals, places or things. For example: Eze, lion, Ibadan, bench, etc.

Note: Proper Nouns usually started with capital letters. However, this is not so in all cases, for example 'lion' and 'bench', as seen above.

2.  Common Nouns
Common Nouns are generally names of people, animals, places or things. Examples include: humans, boys, girls, woman, men, animals, furniture, cities, countries, towns, foods, etc.

3.  Abstract Nouns
Abstract Nouns are names given to things we cannot see but only know they exist when we feel them. They are not tangible nouns. Examples include: air, love, happiness, joy, etc.

4.  Concrete Nouns
Concrete Nouns are nouns we can see, feel, and touch. They are tangible nouns. Examples include: chair, table, book, road, football, etc.

5.  Collective Nouns
Collective Nouns are names given to a group of items of the same kind. It could also be a group of people. Examples include: cutlery, furniture, jewelry, crowd, spectators, audience, congregation, and mob. Other examples include:
A bunch of keys
A held of cattle
A shoal of fish
A bevy of ladies
A band of musician
A crew of sailors
A gang of thieves/prisoners/workmen
A flock of sheep
A covey of birds
A drove of horses
A team of oxen
A muster of peacocks
A pack of wolves
A leap of leopards
A gaggle or geese
A swarm of locusts
A hive of bees
A suite of furniture
A set of tools
A plague of insects
An anthology of poems
A library of books
A bouquet of flowers
A forest of trees, etc.

Note the following:
'Congregation' is a number of people in a Church, Mosque or Hall.
'Audience' is a number of people in a theatre, concert or cinema who are watching and listening.
'Spectators' are a number of people in a field or stadium watching without listening.
'Assembly' is a number of people gathered for some common purpose.
'Crowd' is a number of people gathered in the street.
'Mob' is a number of people protesting.

In the next article we are going to write about singularity and plurality in Nouns.

Sodium and its compounds

Sodium is a typical alkali metal. It occurs naturally in its ores chiefly as sodium chloride (common salt), sodium trioxonitrate(V) (Chile saltpetre) and sodium trioxocarbonate(IV) (soda ash). Sodium is extracted industrially by the Downs Process. Here, common salt is electrolysed in the molten condition. Calcium chloride is added to common salt to serve as a flux (to bring the melting point of common salt from 800°C to about 600°C). In the molten sodium chloride are Na+ and Cl- ions.

Sodium is used:

i. In the manufacture of lead(IV)tetraethyl, an anti-knock addictive used in petrol.

ii. In sodium vapour lamps (having intensity yellow illumination).

iii. In the production of titanium needed for the manufacture of heat-resistant alloys in rockets.

iv. In an alloy for making coolants for nuclear reactors.

Sodium has some important compounds (e.g NaCl, NaOH, Na2SO4, Na2CO3) that are useful industrially.

1. Sodium chloride (NaCl): When pure, it is not deliquescent (dampness is due to impurities (like MgCl2) which are deliquescent). It is a convenient starting material for manufacturing compounds like caustic soda, washing soda, baking soda and salt-cake. It is also used for the preparation of chlorine gas and hydrogen chloride needed for the manufacture of bleaching agents and fine chemicals. In addition, sodium chloride is used in salting out process in soap making or in solvent extraction of organic substance from water.

2. Sodium hydroxide (NaOH) is prepared industrially by the electrolysis of brine (a saturated solution of sodium chloride). The pellet is deliquescent. Its dissolution in water is exothermic. The resulting aqueous solution is alkaline (turns red litmus blue).

Sodium hydroxide is used in the manufacture of soaps (saponification). It is also used in the textile industries for treatment of cotton. Also, an aqueous sodium hydroxide solution is used in qualitative analysis to form the hydroxides of metal ions in solution as precipitates. This facilitates the identification of some actions in unknown samples.

3. Sodium tetraoxosulphate(VI) (Na2SO4):

It is prepared in the laboratory by neutralizing sodium hydroxide solution by dilute H2SO4. The hydrated form is the Glauber's salt, Na2SO4.10H2O.

Sodium tetraoxosulphate(VI) is used:

i. In the manufacture of glass (a mixture of two silicates e.g. Na2SiO3 and CaSiO3)/

ii. In the manufacture of sodium sulphide (by heating it with coke).

Sodium sulphide is used for stripping the hair from hides and for making shaving powder.

iii. In drying the ethereal layer during solvent extraction of organic compounds from water.

4. Sodium trioxocarbonate(IV) (Na2CO3):

It is obtained industrially by the Solvay process. The raw materials are concentrated brine (NaCl), ammonia gas (NH3) and limestone (CaCO3) which yields quicklime (CaO) and carbon(IV)oxide (CO2) when heated. The process involves essentially the following steps:

i. formation of ammoniacal brine when brine is saturated with ammonia gas.

ii. Reaction between the ammoniacal brine and carbon (IV) oxide (produced by heating limestone) to form sodium hydrogen trioxocarbonate(IV) and ammonium chloride.

iii. Sodium hydrogen trioxocarbonate (IV) (not very soluble in water) is filtered from the reaction mixture and the washed.

iv. Heating of sodium hydrogen trioxocarbonate (IV) to sodium trioxocarbonate (IV) and carbon (IV) oxide (which is recycled). Sodium trioxocarbonate (IV) is stable to heat i.e. not decomposed on heating.

v. If the anhydrous sodium trioxocarbonate (IV) (soda ash) is dissolved in hot water and allowed to cool, it gives the crystalline form (washing soda).

The important uses of sodium trioxocarbonate (IV) are:

i. Softening of water for domestic purposes.

ii. Manufacture of glass (formation of silicates). The mixture of Na2SiO3, CaSiO3 and unreacted SiO2 constituent the glass.

iii. Manufacture of caustic soda.

Calcium and its compounds

Calcium is a typical alkali earth metal. It occurs as calcium trioxocarbonate (IV) in different forms: chalk, limestone, marble, calcite, Iceland spar and aragonite. It also occurs as calcium tetraoxosulphate (VI) e.g. gypsum, anhydrite. However, it is extracted industrially by the electrolysis of calcium chloride (a by-product from Solvay process), using graphite anode (also the container) and iron cathode. It is a silvery white metal. The density is 1.55g per cm3 and the melting point is about 850°C. It is not as reactive as sodium and so it is not necessary to keep it below the surface of petroleum oil (in contrast to sodium). However, a white film of oxide is formed on the surface on exposure to air. Calcium compounds generally burn with s brick-red flame.

Some of the important reaction of calcium are:

i. In air: it forms calcium oxide (quicklime).

ii. With water: calcium metal is used in the extraction of thorium and in steel casting (as deoxidizer). The important compounds of calcium are calcium oxide (CaO), calcium hydroxide (Ca(OH)2), calcium trioxocarbonate (IV) (CaCO3), calcium tetraoxosulphate (VI) (CaSO4) and calcium chloride (CaCl2).

1. Calcium oxide (lime, quicklime) CaO, is a white solid, made industrially by the action of strong heat on limestone (CaCO3).

It is a refractory substance (it will not melt even when heated to a very high temperature) hence its use in producing light (limelight). Its important reactions are:

i. With water, slaked lime Ca(OH)2 is formed.

This reaction is called slaking. The slaked lime is changed to lime-water if water is added and filtered..

Because quicklime is basic and hygroscopic, it is used as the drying agent for ammonia gas.

ii. With silica: CaO + SiO2 —> CaSiO3

2. Calcium hydroxide, Ca(OH)2 is a white powder, prepared by addition of water to calcium oxide. Its dissolution in water is exothermic. It is sparingly soluble in water but the solubility decreases with increasing temperature. It is basic hence gives reactions expected of bases (e.g. neutralization with aqueous mineral acids). The compound is useful in many ways:

i. In agriculture, to reduce acidity in soils (liming).

ii. In preparation of calcium trioxocarbonate (IV) e.g. chalk.

iii. In the making of mortar by builders.

3. Calcium trioxocarbonate (IV), CaCO3, occurs naturally as marble, chalk, limestone and in many other forms such as stalagmites and stalactites from the roof and floor of carvers. It is a white solid which is practically insoluble in water. Some of its reactions are:

i. With dilute acids (HCl and HNO3); it evolves carbon (IV) oxide (CO2).

ii. With water containing dissolved CO2, it dissolves to give soluble calcium hydrogentrioxocarbonate(IV):

Calcium trioxocarbonate (IV) is used:

i. In the extraction of iron using the blast furnace.

ii. In the manufacture of cement.

iii. In the Solvay process of manufacturing sodium trioxocarbonate (IV).

4. Calcium tetraoxosulphate (VI), CaSO4, is a white solid. It occurs naturally as anhydrite (CaSO4) and gypsum (CaSO4.2H2O), known as plaster of Paris (POP). This involves heating gypsum to a temperature between 100°C and 200°C.

Plaster of Paris is used medically in making casts to maintain joints in a fixed position. It is used industrially for cement and wall-plasters.

5. Calcium chloride, CaCl2, is a white solid. The solution is prepared by adding marble to dilute HCl until a little of marble remains.

The mixture is filtered. The evaporation of the filtrate to dryness gives the fused solid (anhydrous CaCl2). This is very deliquescent hence its use as a drying agent for most gases (except ammonia with which it reacts).

Calcium and its compounds

Calcium is a typical alkali earth metal. It occurs as calcium trioxocarbonate (IV) in different forms: chalk, limestone, marble, calcite, Iceland spar and aragonite. It also occurs as calcium tetraoxosulphate (VI) e.g. gypsum, anhydrite. However, it is extracted industrially by the electrolysis of calcium chloride (a by-product from Solvay process), using graphite anode (also the container) and iron cathode. It is a silvery white metal. The density is 1.55g per cm3 and the melting point is about 850°C. It is not as reactive as sodium and so it is not necessary to keep it below the surface of petroleum oil (in contrast to sodium). However, a white film of oxide is formed on the surface on exposure to air. Calcium compounds generally burn with s brick-red flame.

Some of the important reaction of calcium are:

i. In air: it forms calcium oxide (quicklime).

ii. With water: calcium metal is used in the extraction of thorium and in steel casting (as deoxidizer). The important compounds of calcium are calcium oxide (CaO), calcium hydroxide (Ca(OH)2), calcium trioxocarbonate (IV) (CaCO3), calcium tetraoxosulphate (VI) (CaSO4) and calcium chloride (CaCl2).

1. Calcium oxide (lime, quicklime) CaO, is a white solid, made industrially by the action of strong heat on limestone (CaCO3).

It is a refractory substance (it will not melt even when heated to a very high temperature) hence its use in producing light (limelight). Its important reactions are:

i. With water, slaked lime Ca(OH)2 is formed.

This reaction is called slaking. The slaked lime is changed to lime-water if water is added and filtered..

Because quicklime is basic and hygroscopic, it is used as the drying agent for ammonia gas.

ii. With silica: CaO + SiO2 —> CaSiO3

2. Calcium hydroxide, Ca(OH)2 is a white powder, prepared by addition of water to calcium oxide. Its dissolution in water is exothermic. It is sparingly soluble in water but the solubility decreases with increasing temperature. It is basic hence gives reactions expected of bases (e.g. neutralization with aqueous mineral acids). The compound is useful in many ways:

i. In agriculture, to reduce acidity in soils (liming).

ii. In preparation of calcium trioxocarbonate (IV) e.g. chalk.

iii. In the making of mortar by builders.

3. Calcium trioxocarbonate (IV), CaCO3, occurs naturally as marble, chalk, limestone and in many other forms such as stalagmites and stalactites from the roof and floor of carvers. It is a white solid which is practically insoluble in water. Some of its reactions are:

i. With dilute acids (HCl and HNO3); it evolves carbon (IV) oxide (CO2).

ii. With water containing dissolved CO2, it dissolves to give soluble calcium hydrogentrioxocarbonate(IV):

Calcium trioxocarbonate (IV) is used:

i. In the extraction of iron using the blast furnace.

ii. In the manufacture of cement.

iii. In the Solvay process of manufacturing sodium trioxocarbonate (IV).

4. Calcium tetraoxosulphate (VI), CaSO4, is a white solid. It occurs naturally as anhydrite (CaSO4) and gypsum (CaSO4.2H2O), known as plaster of Paris (POP). This involves heating gypsum to a temperature between 100°C and 200°C.

Plaster of Paris is used medically in making casts to maintain joints in a fixed position. It is used industrially for cement and wall-plasters.

5. Calcium chloride, CaCl2, is a white solid. The solution is prepared by adding marble to dilute HCl until a little of marble remains.

The mixture is filtered. The evaporation of the filtrate to dryness gives the fused solid (anhydrous CaCl2). This is very deliquescent hence its use as a drying agent for most gases (except ammonia with which it reacts).

Allotropes, Alloys and Ores of metals and non-metals

Both metals and non-metals show polymorphism or allotropy. This is the occurrence of an element in more than one form but in the same physical state. These forms are called polymorphs or allotropes.

Elements                      Major Allotropic Forms

Carbon                          Diamond and Graphite

Sulphur                          Rhombic sulphur

                                        Monoclinic sulphur

Tin                                  White tin and Red tin

Oxygen                           Dioxygen (Oxygen)

                                        Trioxygen (Ozone)

Phosphorus                   White phosphorus

                                         Red phosphorus

All the allotropes of an element have the same chemical properties even though they have different appearances or crystalline strictures. For instance, diamond (a hard form of carbon) and graphite (a soft form of carbon) can be shown to be the same element by combustion whereby a sample of each allotrope is burnt in excess oxygen. The product in each case is carbon(IV)oxide.

Metals are at times mixed intimately with other metals or non-metals to form alloys. The alloys combine the strength and the properties of the constituent elements.

Examples:

Alloys                       Constituent Elements

Brass                            Copper and Zinc

Bronze                          Copper and Tin

Steel                              Iron and Carbon

Duralumin                    Aluminum, Magnesium,

                                      Manganese and Copper

Sodium Amalgam       Sodium and Mercury

Zinc Amalgam              Zinc and Mercury

It should be noted that an amalgam is an alloy of mercury and another metal.

The form in which a metal occurs naturally is known as the ore. Metals can be removed or extracted from their ores by various means depending on their degree of activity. The activity series is the arrangement of elements in the decreasing order of reactivity or electropositivity or metallicity.

Those metals that are highly or moderately reactive do not occur free in nature but rather they occur in form of compounds in their ores.

The compounds found in ores are usually oxides or sulphides or trio of at on area (IV) of metals. These ores are either concentrated (by floatation) or roasting (heating in air) and then reduced chemically or electrolytically to release or free their metals. Elements in this category include potassium, sodium, calcium, aluminium and iron.

Ores                          Element sought

Haemitite                          Iron

Casseterite                       Tin

Bauxite                        Aluminum

Zinc blend                        Zinc

Galena                             Lead

Malachite                      Copper

However, there are other metals that have low reactivity and so they are usually found free in nature. Such metals include Platinum and Gold.

Metalloid are elements that are neither distinctly metallic nor clearly non-metallic e.g. Silicon, Arsenic, Tellurium, etc. The properties of metalloids are intermediate between those of metals and those of non-metals. For instance, they are semiconductors rather than being good conductors or nonconductors of electricity.

Deliquescent, Hygroscopic and Efflorescent Compounds

These are substances composed of two or more kinds of atoms (elements) joined together in a definite grouping.

The properties of a compound are distinct and different from those of the individual elements that are combined in its make-up.

There are several millions of compounds known. These compounds are derived from the elements e.g. water consists of hydrogen and oxygen atoms in ratio 2 to 1; common salt consists of sodium and chlorine atoms in ratio 1 to 1.

Compounds are usually classified in a number of ways:

Based on the behavior when exposed to the atmosphere, compounds are classified into three: deliquescent, hygroscopic and efflorescent.

Deliquescent compounds are those compounds that absorb moisture from the atmosphere and form the solutions of tjr compounds e.g. sodium hydroxide pellets, anhydrous calcium chloride and iron(III)chloride.

Hygroscopic compounds are those that absorb moisture from the atmosphere and become wet. Their ability to absorb water from air is less than that of deliquescent compounds. Hence the solid ones from pasty substances and not solution while the liquid ones become diluted e.g. sodium trioxonitrate(V), copper(II)oxide and concentrated tetraoxosulphate(VI)acid.

Efflorescent compounds are compounds that give out their water of crystallization to the atmosphere at ordinary temperatures e.g. sodium trioxocarbonate(IV)decahydrate loses nine of its ten moles of water of crystallization on exposure to air.

It should be noted that all deliquescent substances are also hygroscopic but not all hygroscopic substances are deliquescent. Hygroscopy is the ability of a substance to draw water vapour to itself and become wet. Both hygroscopic and deliquescent substances have this ability.

However, if a substance goes beyond being wet and becomes a solution in the course of drawing water to itself, it shows deliquescency.

Deliquescent and hygroscopic compounds are used as drying agents for gases in the laboratory. For instance, concentrated tetra of soul phage(VI)acid is the usual drying agent for acidic gases e.g. sulphur(IV)oxide, calcium oxide is commonly used as the drying agent for the alkaline gas, ammonia. Also, desiccants in desiccators are deliquescent or hygroscopic substances e.g. silica gel, calcium oxide, fused calcium chloride and phosphorus(V)oxide.

Physical and chemical properties of metals and non-metals

There are distinct substances that cannot be spit-up into simpler substances. Such substances consist of only one kind of atom. There are over one hundred elements known to date. Each of the elements is usually symbolized by a capital letter or a capital letter followed by a small letter derived from the English or Latin or Greek name of the element concerned e.g. Hydrogen (H), Sodium (Na), Copper (Cu), Uranium (U), Antimony (SB), Neon (Be), etc.

The elements can be categorized in several ways.

- Based on natural radioactivity, elements are classified into two: radioactive and non-radioactive elements.

Radioactive elements are those that undergo a spontaneous decay or degradation followed by the emission of one or more of the radiations (Alpha, Betta, Gamma).

Such elements include Radium (Ra), Uranium (U), Francium (Fr), Polonium (Po) and Thorium (Th).

Non-radioactive elements do not degrade or emit any radiations. They have stable nuclei and would therefore not undergo radioactive decay e.g. Sodium (Na), Calcium (Ca), etc.

- Based on properties, elements are classified into three: metal, non-metals, and metalloids.

Metals are elements that are ionized by electron loss e.g. Potassium, Sodium, Calcium, lead, etc.

They possess the following physical properties:

i. Ductility and malleability. Hence they are useful in making wire cables and fabrication in construction works.

ii. Good conductor of heat and electricity due to the presence of free mobile electrons in their lattice. They are therefore useful in making cooking pots, boilers and electric cables.

iii. Hard solids with high melting points/boiling points except sodium, which is soft, and mercury, which is a liquid metal.

iv. Lustrous (with silvery colour) hence useful in jewelry and in metallic paints because of its reflectivity.

v. Some of them make a sound note, when struck (sonorous) e.g. copper, iron, and aluminum. Such metals are therefore useful in making musical instruments.

vi. None of the metals are soluble in any ordinary solvent without a chemical change.

The general chemical properties of metal are:

i. Electropositive i.e. loss electron(s) to become ionized hence reducing agents.

ii. Most of the metal s combine with oxygen to form basic oxides e.g. CuO, MgO and CaO. However some metallic oxides are amphoteric e.g. ZnO, PbO. Such oxides react as both acid and base.

iii. Combine with chlorine to form electrovalent chloride e.g. NaCl.

iv. Form metallic hydrides that are ionic.

v. Replace the hydrogen in an acid if more than electropositive than hydrogen.

Non-metals are elements that ionize by electron gain e.g. hydrogen, oxygen, chlorine, bromine, carbon, etc.

Non-metals are therefore oxidizing agents (except a few of them) since they undergo reduction in their ionization process

The general physical properties of non-metals are:

i. Brittle i.e cannot be hammered into sheets (non-mallaeble) or drawn into wires (non-ductile).

ii. Non-conductors of heat and electricity because they do not possess free mobile electrons. However, graphite (a form/allotrope of Carbon) is a good conductor of electricity because it contains free mobile electrons in its lattice.

iii. Mainly gases (e.g. hydrogen, oxygen, nitrogen, chlorine) though some of them exist as solids or liquids. For instance, bromine is a liquid at room temperature, iodine is a soft violet solid, sulphur is a yellow solid, graphite and diamond are solids. While graphite is soft, diamond is the hardest known natural substance.

iv. Most of the non-metals are dull and cannot be polished but diamond (an allotropic firm of carbon) can be polished (lustrous) and can therefore used in jewelry.

v. Non-sonorous.

vi. Have low density though some of them are heavy e.g. diamond.

vi. Some non-metals dissolve slightly in water without reaction (e.g. oxygen) though some of them dissolve with water (e.g. chlorine, bromine).

Some of the general chemical properties of non-metals are:

i. They are mainly oxidizing agents.

ii. Form acidic oxides mainly e.g. carbon(IV)oxide, sulphur(IV)oxide, nitrogen(IV)oxide. The acidic oxides are known as acid anhydrides (compounds that dissolve in water to produce an acidic solution or a solution whose pH is less than 7).

iii. Non-metals combine with other non-metals to form covalent compounds e.g. ammonia, carbon(IV)oxide, hydrogen chloride.

Heating profile of a solid

The temperature at which vibrations of a particles of a solid become so great such that the mutual attractive forces are overcome and the particles break free from the fixed lattice positions and slide over one another in a liquid state is called melting point (m. pt). At this point, the solid state and the liquid phases are in equilibrium. Even though heat is continuously supplied to the solid, the temperature is constant at the time of melting.

Generally, the heat absorbed by a substance in changing from one phase to another is called the latent heat (hidden heat). The amount of heat absorbed, which causes the change of phase to occur at the melting point, is called the heat of fusion. The magnitude of this heat energy depends on the nature of the solid and the strength of the attractive forces between particles.

When heated, some solids however vaporize directly without passing through the liquid phase. On cooling, the vapour also turns to the solid phase. The phenomenon is known as sublimation. Solids having usually high vapour pressure exhibit this property. Examples of such solids include iodine crystal, ammonium chloride crystal, naphthalene, camphor and dry ice (solid carbon (IV) oxide).

Similarly, boiling point (b. pt) is the at which the liquid and vapour phases are in equilibrium. The boiling point of a liquid depends on the prevailing external atmospheric pressure. The lower the external pressure, the lower the boiling point of a liquid and vice-versa. The amount of heat absorbed that causes change of phase (liquid – vapour) to occur at the boiling point is the heat of vaporization.

Properties of Matter

Properties tell us what a substance is or what a substance can do. The properties of matter are classified as either physical or chemical.

Physical properties tell us everything about what a substance is, when no change is occurring to its constituents. Such properties are observed with our senses or instruments or pieces of apparatus. Examples are: state of matter, colour, odour, taste, texture, hardness, solubility in water, melting point, boiling point, density, viscosity and spectroscopic patterns (IR, UV, NMR).

Chemical properties are those properties that tell us about what a substance can do as regards to whether or not the substance reacts with other substances. Examples are flammability, rusting of iron, precipitation, decomposition of water by an electric current.

Changes of Matter

The changes that matter undergoes are associated with properties. The change are therefore categorized into physical and chemical.

A physical change is one that alters the physical properties of matter (particularly the form and state). In many cases, the changes of state is easily reversible. Examples are changes of state such as boiling, melting, freezing, condensation, sublimation, magnetization of metals, breaking glass and cutting wood.

A  chemical change is one in which new kind of matter is formed. It us always accompanied by energy changes (evolution or absorption of energy in form of heat or light or both). The process is not easily reversible. Examples are: combustion, rusting of iron, precipitation and souring of milk.

Classification of Matter

Matter is anything that has mass and occupies space i.e everything seen or unseen.

On a broad basis, matter can be subdivided into two general categories: pure or distinct substances and impure substances (mixtures).

Pure substances are distinct substances having the following general properties:

i. All parts are the same throughout (homogeneous).

ii. Composition is definite.

iii. They cannot be easily separated by physical means.

iv. Separation by physical methods is not easy.

v. They have a unique set of physical properties (boiling point, melting point, density, physical state, spectroscopic properties, etc.).

Physical properties are, in fact, used as the criteria for determining the purity level of substances. Pure solid substances have sharp melting point or very narrow melting range (Example: a reasonable pure benzoic acid sample has a melting point of 122°C or a melting range 120°C to 122°C). However, impurities (contaminants) cause a depression in melting points and widening of the melting range of solid substances (Example: an impure sample of benzoic acid has a melting range 110°C to 118°C).

For liquid, the criterion for determining the purity level of samples is the boiling point or relative density. A reasonable pure liquid has a constant boiling point or a low boiling range (Example: 99°C or 98°C to 100°C for distilled water). Impurities cause an elevation of the boiling point and the widening of the boiling range of a hitherto pure liquid (Example: 99°C to 105°C for an impure water sample).

Pure substances are either elements or compounds.

State of Matter and Phase Changes

Chemist usually describe substances as matter. Each form of Matter is made up of aggregates of small particles called molecules. Molecules consist of one or more tiny particles called atoms. A molecules may be monoatomic (e.g. He, Ne, Ar) or diatomic (e.g. H2, O2, N2, Cl2) or polyatomic (e.g. O3, P4, S8). Hence:

Atoms >>> Molecules >>> Matter

Matter exists in three phases commonly referred to as the states of matter. These are gas, liquid and solid.

The particles (molecules) of a gas are very far apart and are held together by very weak attractive forces, those of a liquid are much more closely held together by stronger attractive forces, those of solid are most closely held together by very strong attractive forces.

The phase transfer processes are freezing, melting, boiling, condensation and sublimation.

Solid     >>>     Liquid     (Melting)

Liquid    >>>     Solid      (Freezing)

Liquid    >>>     Vapour    (Boiling)

Vapour   >>>     Liquid     (Condensation)

Solid     >>>     Vapour    (Sublimation).

We are going to learn more about matter in the next article