C5- Chemical Changes

Question 1

1. What do metals react with to produce oxides? (1 mark)

Answer 1

• Metals react with oxygen to produce metal oxides.

Question 2

2. What are these reactions called? (1 mark)

Answer 2

• The reactions are oxidation reactions because the metals gain oxygen.

Question 3

3. What is the opposite of oxidation? (1 mark)

Answer 3

• The opposite process to oxidation is reduction, or the loss of oxygen.

Question 4

4. What type of species do metals form when they react with another substance? (1 mark)

Answer 4

• A positive ion.

Question 5

5. What is the Reactivity Series of Metals? (1 mark)

Answer 5

• It is a list showing the tendency of metals to form positive ions. The more likely they are to form positive ions, the higher on the list they are.

Question 6

6. What can a more reactive metal do? (1 mark)

Answer 6

• A more reactive metal can displace a less reactive metal from a compound.

Question 7

7. What is the term REDOX? (2 marks)

Answer 7

• REDOX is the processes of REDuction and OXidation. Oxidation is the loss of electrons and reduction is the gain of electrons.

Question 8

8. Where do we get the metals that we use? (1 mark)

Answer 8

• The Earth’s crust

Question 9

9. The method of extracting the metal depends on what? (1 mark)

Answer 9

• The reactivity of the metal.

Question 10

10. Name 3 metals that are found in the Earth’s crust as the metal themselves (in their native state). (3 marks)

Answer 10

• Gold
• Silver
• Platinum

Question 11

11. How do we extract metals from their ores that are less reactive than carbon? (1 mark)

Answer 11

• Heat them with carbon.

Question 12

12. When a metal reacts with an acid, what is produced? (1 mark)

Answer 12

• Acids react with some metals to produce salts and hydrogen.

Question 13

13. What happens when an acid reacts with an alkali? (2 marks)

Answer 13

• Acids are neutralised by alkalis (e.g. soluble metal hydroxides) and bases (e.g. insoluble metal hydroxides and metal oxides) to produce salts and water, and by metal carbonates to produce salts, water and carbon dioxide.

Question 14

14. What does the salt produced in a reaction depend on? (2 marks)

Answer 14

• The particular salt produced in any reaction between an acid and a base or alkali depends on:

• The acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates)
• The positive ions in the base, alkali or carbonate.

Question 15

15. How are soluble salts made? (4 marks)

Answer 15

• Soluble salts can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides or carbonates.

Question 16

16. In general, how are soluble salts prepared? (3 marks)

Answer 16

• The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt. Salt solutions can be crystallised to produce solid salts.

Question 17

17. What do acids produce in aqueous solution? (1 mark)

Answer 17

• Acids produce hydrogen ions (H+) in aqueous solutions.

Question 18

18. What do alkalis produce in aqueous solution? (1 mark)

Answer 18

• Aqueous solutions of alkalis contain hydroxide ions (OH–)

Question 19

19. What does the pH scale measure? (2 marks)

Answer 19

• The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution, and can be measured using universal indicator or a pH probe.

Question 20

20. What pH is a neutral solution? (1 mark)

Answer 20

• A solution with pH 7 is neutral.

Question 21

21. What pH does an acid solution have? (1 mark)

Answer 21

• Aqueous solutions of acids have pH values of less than 7

Question 22

22. What pH does an alkaline solution have? (1 mark)

Answer 22

• Aqueous solutions of alkalis have pH values greater than 7.

Question 23

23. What do acids produce in aqueous solution? (1 mark)

Answer 23

• Acids produce hydrogen ions (H+) in aqueous solutions.

Question 24

24. What do alkalis produce in aqueous solution? (1 mark)

Answer 24

• Aqueous solutions of alkalis contain hydroxide ions (OH–).