S2 Chemistry

Question 1

What are the signs of a chemical reaction?

Answer 1

A colour change
A temperature change
A gas being released - look for fizzing or bubbles
A solid being formed

Question 2

What can you do to increase the speed of a reaction?

Answer 2

Decrease the particle size
Increase temperature
Increase concentration
Adding a catalyst

Question 3

What is a catalyst?

Answer 3

A catalyst is a substance which speeds up a chemical reaction & is not used up in the reaction.

Question 4

What is the name of a biological catalyst?

Answer 4

The catalyst present in living things are enzymes, sometimes also called biological catalysts.

Question 5

Magnesium + _ _ _ _ _ _ = Magnesium Oxide

Answer 5

Oxygen

Question 6

Carbon + _ _ _ _ _ _ = Carbon dioxide

Answer 6

Oxygen

Question 7

Oxygen + _ _ _ _ _ _ = water

Answer 7

Hydrogen

Question 8

If a substance has a pH of 3 is this an acid or an alkali?

Answer 8

A substance with a pH of 3 is an acid.

Question 9

If a substance has a pH of 14 is this an acid or an alkali

Answer 9

A substance with a pH of 14 is an alkali.

Question 10

A substance with a pH of 7: Is this an acid or an alkali?

Answer 10

A substance with a pH of 7 is neutral.

Question 11

A substance with a pH of 7.4: Is this an acid or an alkali?

Answer 11

A substance with a pH of 7.4 is an alkali.

Question 12

Which pH range do gastric juice have?
a) Around pH 2
b) Around pH 7
c) Around pH 9

Answer 12

a) Gastric juices have a pH around 2.

Question 13

Which pH range do hand soap or cleaning fluids that contain bleach have?
a) Around pH 2-3
b) Around pH 7
c) Around pH 10-12

Answer 13

c) Hand soap or cleaning fluids that contain bleach have a pH of around pH 10-12.

Question 14

What colour does red cabbage indicator turn when you add acids?

Answer 14

Red cabbage indicator turns pink when you add acids.

Question 15

What colour does red cabbage indicator turn when you add alkalis?

Answer 15

Red cabbage indicator turns green when you add alkalis.

Question 16

What colour does red cabbage indicator turn when you add a neutral substance?

Answer 16

Red cabbage indicator stays purple when you add a neutral substance.

Question 17

Write the word equation that shows what happens when an acid and an alkali react.

Answer 17

An acid an an alkali neutralise and form salt and water:
acid + alkali –> salt + water

Question 18

What type of salt is produced by hydrochloric acid?

Answer 18

Hydrochloric acids produce chlorides.

Question 19

What type of salt is produced by sulfuric acid?

Answer 19

Sufuric acid produces sulfates.

Question 20

What type of salt is produced by nitric acid?

Answer 20

Nitric acid produces nitrates.

Question 21

Write the word equation when sodium hydroxide (an alkali) reacts with hydrochloric acid.

Answer 21

Sodium hydroxide + hydrochloric acid
–>
Sodium chloride + water

Question 22

Write a chemical reaction for this example:
Hydrogen reacting with oxygen to produce water.

Answer 22

Hydrogen + Oxygen –> Water

Question 23

Write a chemical reaction for this example:
Sodium chloride is produced by reaxcting sodium and chlorine.

Answer 23

Sodium + Chlorine –> Sodium chloride

Question 24

Chemical reaction? Yes or No?
A solid forming when two solutions are added together.

Answer 24

Yes, this is a chemical reaction.

Question 25

Chemical reaction? Yes or No? Separating chalk from water.

Answer 25

No, this is a physical separation, not a chemical reaction.

Question 26

Chemical reaction? Yes or No? A puddle evaporating.

Answer 26

No, this is a physical change of state, not a chemical reaction.

Question 27

Chemical reaction? Yes or No? Making magnesium and oxygen from magnesium oxide.

Answer 27

Yes, this is a chemical reaction.

Question 28

Chemical reaction? Yes or No? Adding calcium to water - it fizzes and gets hot.

Answer 28

Yes, this is a chemical reaction.

Question 29

In which experiment would the aspirin take the longest to dissolve? a) aspirin tablet, water at 20 degrees C b) aspirin powder, water at 40 degrees C c) aspirin powder, water at 30 degrees C d) aspirin tablet, water at 40 degrees C.

Answer 29

a) Explanation: Using a tablet instead of powder decreases the rate of reaction; the lower temperature also decreases the rate of reaction

Question 30

Which two experiments should be compared to show the effect of particle size on the speed of dissolving? a) aspirin tablet, water at 20 degrees C b) aspirin powder, water at 40 degrees C c) aspirin powder, water at 30 degrees C d) aspirin tablet, water at 40 degrees C.

Answer 30

b & d Explanation: The temperature needs to stay the same (40 degrees) as it is a controlled variable; the only thing changing (the independent variable) is aspirin powder vs aspirin tablet.

Question 30

Nitric acid reacts with an alkali to form sodium nitrate and water. What is the alkali?

Answer 30

Sodium hydroxide

Question 30

Lithium chloride is made when lithium hydroxide reacts with which acid?

Answer 30

Hydrochloric acid

Question 30

Why can experiments c and d not be used to investigate the effect of particle size on dissolving? a) aspirin tablet, water at 20 degrees C b) aspirin powder, water at 40 degrees C c) aspirin powder, water at 30 degrees C d) aspirin tablet, water at 40 degrees C.

Answer 30

The temperature is also changing, so the results would be invalid. Only one thing (the particle size, i.e. powder vs tablet) should change to get valid results.

Question 30

Sulfuric acid and sodium hydroxide react. What is the salt called that is made in this reaction?

Answer 30

Sodium sulfate

Question 30

Copper carbonate solution (green) is easily decomposed by heating. As a result, the solid copper oxide (black) is formed and the gas carbon dioxide is also released. What signs of a chemical reaction are shown in this example?

Answer 30

There is a colour change (green to black), a solid is formed and a gas is released.