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Name _________________________________________

Chemistry Grade 7 Part 2

1. The following diagram shows the path of a gas particle moving through air.

a. Why does the particle only move a short distance in any particular direction?

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b. What word describes the changes of direction of the particle?

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c. Draw a diagram to show the path a gas particle would take through a vacuum.

d. How does the motion of a gas particle change if the temperature is increased?

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2 In the following experiment a piece of cotton wool soaked in ammonia was placed at one end of a long glass tube and a piece of cotton wool soaked in hydrochloric acid was placed at the other. The tube was sealed.

a. What name is given to the process by which particles of one substance move through particles of another?

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b. Ammonia vapour and hydrochloric acid vapour react to form a white ‘smoke’ in the tube. Complete the following equation for the reaction that takes place.

ammonia + hydrochloric acid → ammonium ..........................................

c. Suggest why the white ‘smoke’ appears in the tube nearer to the end containing the hydrochloric acid.

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Chemical change or physical change?

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Chemical change or physical change (continued)

3. a. Diagram A shows a __________________ change while diagram B shows a _____________

change. Explain:

b. Process A needs 286 kJ energy while process B only needs 44 kJ energy for the same amount of water.

Explain the difference in the amount of energy needed.

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Elements, compounds and mixtures

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Naming compounds

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Word equations

The following box contains the names of some elements.

aluminium bromine chlorine hydrogen

iodine iron lithium magnesium

oxygen sodium sulfur

Choose which elements would be needed to make each of the following compounds and write a word equation for the reaction.

3 We could make sodium oxide

by reacting ............................................ and .........................................................

Word equation: .....................................................................................................

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4 We could make iron sulfide

by reacting ............................................ and .........................................................

Word equation: .....................................................................................................

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5 We could make magnesium chloride

by reacting ............................................ and .........................................................

Word equation: .....................................................................................................

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6 We could make aluminium iodide

by reacting ............................................ and .........................................................

Word equation: .....................................................................................................

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7 We could make lithium bromide

by reacting ............................................ and .........................................................

Word equation: .....................................................................................................

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8 We could make hydrogen sulfide

by reacting ............................................ and .........................................................

Word equation: .....................................................................................................

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7. List the reactants and product:

iron + chlorine iron chloride

Reactants:

Product:

8. Complete the word equation:

Potassium + chlorine

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Compounds and mixtures

Use only the word ‘mixture’ or ‘compound’ to complete each of the following sentences.

9 A ..................................... does not have a fixed composition.

10 The properties of a ..................................... are different to the properties of the

substances from which it is made.

11 Air is a ..................................... .

12 It is often possible to separate the components of a ..................................... by physical

methods.

13 A ..................................... has its own chemical formula.

14 Sodium chloride is a ..................................... .

15 In a ..................................... the components are always present in the same fixed

proportions.

16 Distilled water is a ..................................... .

17 To separate the components of a ..................................... a chemical reaction is needed.

18 In a ..................................... there are no chemical bonds between particles of the

components.

19 The properties of a ..................................... are the same as the sum of the properties of

its components.

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Periodic Table practice questions

Use the Periodic Table to answer the following questions.

20 Write down the names of the elements in the same group as sodium.

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21 Write down the symbols of the elements in the same group as chlorine.

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22 Name the element that is to the immediate right of potassium.

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23 Give the symbol of the element that is to the immediate left of oxygen.

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24 Give the name and the symbol of the element that is in both Group 3 and Period 3.

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25 In which group is argon?

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26 In which period is sulfur?

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27 Give the number of a group that contains a gas, a liquid and a solid.

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28 Give the number of a group that contains only metals.

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29 Give the name and the symbol of the element with the smallest atomic mass.

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Elements and atoms

Here are four important words:

Atom Compound Element Molecule

30 Use two of these words to describe the underlined word in each of the following sentences:

a. Hydrogen burns in oxygen to form water.

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b. Magnesium reacts with oxygen to form magnesium oxide.

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c. Helium is used to fill balloons that rise in the air.

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d. Hydrogen reacts with chlorine to form hydrogen chloride.

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e. Methane burns in air to produce carbon dioxide and water.

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f. When dilute hydrochloric acid is added to calcium carbonate, carbon dioxide gas is produced.

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g. When dilute hydrochloric acid is added to zinc, hydrogen gas is produced.

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h. Iron reacts with sulfur to form iron sulfide.

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Forming compounds

Lots of compounds can be made by reacting together a metal and a non-metal.

To name the compound we simply add the names of the metal and the non-metal. But we must also change the ending of the non-metal like this:

Oxygen forms oxides

Sulfur forms sulfides

Chlorine forms chlorides

Bromine forms bromides

Name the compounds formed from these metals and non-metals. The first one is done for you.

Metal Non-metal Name of compound

1 Iron Sulfur Iron sulfide

2 Copper Sulfur

3 Zinc Oxygen

4 Magnesium Chlorine

5 Sodium Bromine

6 Copper Oxygen

7 Iron Chlorine

8 Calcium Oxygen