Chemical Changes

Question 1

what is combustion?

Answer 1

the process in which a substance is heated in the presence of oxygen to form one or more new substances

Question 2

what is usually given out during combustion?

Answer 2

heat and light

Question 3

what is thermal decomposition?

Answer 3

the process in which a substance breaks down into two or more simpler substances upon heating

Question 4

what is oxidation?

Answer 4

the process in which a substance gains oxygen and undergoes a chemical change

Question 5

what is neutralisation?

Answer 5

the process in which an acid reacts with an alkali and is neutralised

Question 6

what is produced when an acid reacts with an alkali?

Answer 6

a salt and water

Question 7

what is the word equation for when an acid reacts with an alkali?

Answer 7

acid + alkali → salt + water

Question 8

what is produced when an acid reacts with a metal?

Answer 8

a salt and hydrogen gas

Question 9

what is the word equation for when an acid reacts with a metal?

Answer 9

acid + metal → salt + hydrogen

Question 10

how can you test for hydrogen gas produced in an acid-metal reaction?

Answer 10

by holding a lighted splint above the substances. the splint will extinguish with a ‘pop’ sound in the presence of hydrogen gas

Question 11

what metals do not react with acids?

Answer 11

copper, silver, gold

Question 12

what are carbonates?

Answer 12

ions with 1 carbon and 3 oxygen

Question 13

what is produced when an acid reacts with a carbonate?

Answer 13

salt, carbon dioxide and water

Question 14

what is the word equation for when an acid reacts with a carbonate?

Answer 14

acid + carbonate → salt + carbon dioxide + water

Question 15

what can be used to test for the presence of carbon dioxide in acid-carbonate reactions?

Answer 15

limewater. a white precipitate forms in the presence of carbon dioxide

Question 16

what is the range of the pH scale?

Answer 16

0 - 14

Question 17

what is the pH of acids?

Answer 17

0 - 6

Question 18

what is the pH of the weakest acid?

Answer 18

6

Question 19

what is the pH of the strongest acid?

Answer 19

0

Question 20

what is the pH of alkalis?

Answer 20

8 - 14

Question 21

what is the pH of the weakest alkali?

Answer 21

8

Question 22

what is the pH of the strongest alkali?

Answer 22

14

Question 23

what is the pH of a neutral substance?

Answer 23

7

Question 24

what is the pH of pure water?

Answer 24

7 (neutral)

Question 25

what colour does an acid turn blue litmus paper?

Answer 25

red

Question 26

what colour does an alkali turn red litmus paper?

Answer 26

blue

Question 27

what colour does a neutral substance turn red litmus paper?

Answer 27

it remains the same colour (red)

Question 28

what colour does a neutral substance turn blue litmus paper?

Answer 28

it remains the same colour (blue)

Question 29

name 3 applications of neutralisation

Answer 29

1. antacids are medications that contain alkaline compounds and can neutralise acids in the stomach to relieve discomfort
2. toothpaste is a weak alkali that neutralises acids produced by bacteria in our mouth that cause tooth decay
3. suitable alkaline substances can be added to soil that is too acidic for plants to grow in to neutralise the pH of the soil

Question 30

what is the state symbol for liquid?

Answer 30

(l)

Question 31

what is the state symbol for solid?

Answer 31

(s)

Question 32

what is the state symbol for gas?

Answer 32

(g)

Question 32

what is the state symbol for aqueous?

Answer 32

(aq)

Question 33

do acids contain hydrogen or hydroxide?

Answer 33

hydrogen

Question 34

what is the chemical