You are here: Home End of chapter exercises

## End of chapter exercises

Which of the following can be classified as a mixture:

1. sugar

2. table salt

3. air

4. iron

d.

air

An element can be defined as:

1. A substance that cannot be separated into two or more substances by ordinary chemical (or physical) means

2. A substance with constant composition

3. A substance that contains two or more substances, in definite proportion by weight

4. A uniform substance

d.

A substance that cannot be separated into two or more substances by ordinary chemical (or physical) means

Classify each of the following substances as an element, a compound, a homogeneous mixture, or a heterogeneous mixture: salt, pure water, soil, salt water, pure air, carbon dioxide, gold and bronze.

Salt: Compound

Pure Water: Compound

Soil: Heterogeneous Mixture

Salt Water: Solution

Pure Air: Solution

Carbon Dioxide: Compound

Gold: Element

Bronze: Solution

Look at the table below. In the first column (A) is a list of substances. In the second column (B) is a description of the group that each of these substances belongs in. Match up the substance in Column A with the description in Column B.

Table 1
 Column A Column B 1. iron A. a compound containing 2 elements 2. $H 2 S$ B. a heterogeneous mixture 3. sugar solution C. a metal alloy 4. sand and stones D. an element 5. steel E. a homogeneous mixture

1) D

2) A

3) E

4) B

5) C

You are given a test tube that contains a mixture of iron filings and sulphur. You are asked to weigh the amount of iron in the sample.

1. Suggest one method that you could use to separate the iron filings from the sulphur.

2. What property of metals allows you to do this?

1) Extract the iron filings using a magnet

2) Magnetism

Given the following descriptions, write the chemical formula for each of the following substances:

1. silver metal

2. a compound that contains only potassium and bromine

3. a gas that contains the elements carbon and oxygen in a ratio of 1:2

1) $\text{Ag}$

2) $\text{KBr}$

3) ${\text{CO}}_{2}$

Give the names of each of the following compounds:

1. $NaBr$

2. $Ba(NO 2 ) 2$

3. $SO 2$

4. $H 2 SO 4$

1) Sodium bromide

2) Barium nitrate

3) Sulphur dioxide

4) Hydrogen sulphate (sulphuric acid)

Give the formula for each of the following compounds:

1. iron (II) sulphate

2. boron trifluoride

3. potassium permanganate

4. zinc chloride

1) ${\text{FeSO}}_{4}$

2) ${\text{BF}}_{3}$

3) ${\text{KMnO}}_{4}$

4) ${\text{ZnCl}}_{2}$

For each of the following materials, say what properties of the material make it important in carrying out its particular function.

2. iron burglar bars

3. plastic furniture

4. metal jewellery

5. clay for building

6. cotton clothing

Some suggestions for answers are given. Learners could discuss these questions amongst themselves.

1) High coefficients of friction

2) Inelastic, durable

3) Durable, easily cleaned

4) Shiny, malleable

5) Easily moulded while wet, strong and durable once dry

6) Fibrous, allows skin to “breathe”