8F Reactions

Question 1

State two observations that a chemical reaction is occurring.

Answer 1

Temperature change, colour change, fizzing, smell, irreversible change

Question 2

Describe what an exothermic reaction is.

Answer 2

A reaction which released thermal energy

Question 3

Give one example of an exothermic reaction.

Answer 3

Combustion/burning, metal and acid, neutralisation/acid and alkali

Question 4

What is a neutralisation reaction?

Answer 4

An acid reacts with an alkali

Question 5

What happens in terms of energy when bonds are broken?

Answer 5

Energy is taken in

Question 6

What happens in terms of energy when bonds are made?

Answer 6

Energy is given out

Question 7

True or false: During an exothermic reaction, products have more energy than reactants.

Question 8

How can we measure whether there is a temperature change during a reaction?

Answer 8

Thermometer

Question 9

What happens when bonds in reactants are broken?

Answer 9

Energy is absorbed

Question 10

What happens when bonds in products are made?

Answer 10

Energy is released

Question 11

What are the reactants in an instant cold pack?

Answer 11

Water and ammonium nitrate

Question 12

How does the instant cold pack work?

Answer 12

water and ammonium nitrate react in an endothermic reaction

Question 13

Identify the independent variable during this investigation.

Answer 13

Mass of ammonium nitrate

Question 14

Identify the dependent variable during this investigation.

Answer 14

Temperature change

Question 15

Identify the control variables during this investigation.

Answer 15

Volume of water, the balance reading zero before use

Question 16

How do you calculate the temperature change?

Answer 16

By finding the difference between the before and after temperature

Question 17

What is a catalyst?

Answer 17

A substance that can be added to a chemical reaction to speed it up

Question 18

Why are catalysts described as “specific”?

Answer 18

A catalyst which works for one reaction, will not work for another reaction

Question 19

How do catalysts speed up reactions?

Answer 19

By lowering the activation energy

Question 20

What is an enzyme?

Answer 20

A biological catalyst

Question 21

Give an example of a reaction which is sped up by an enzyme

Answer 21

Digestion, respiration, photosynthesis

Question 22

What is the name of the part of the enzyme which has a specific shape?

Answer 22

Active site

Question 23

Which catalyst is used to manufacture ammonia?

Answer 23

Iron or platinum

Question 24

Give one reason why industrial processes use catalysts

Answer 24

More product made in a shorter time, enzymes can be re-used, lower energy costs during production

Question 25

What are the two reactants of combustion?

Answer 25

Fuel and oxygen

Question 26

In addition to the reactants, what else is needed for combustion?

Answer 26

Heat

Question 27

What are the products of combustion?

Answer 27

Carbon dioxide and water

Question 28

What is a fuel?

Answer 28

A material that burns to release energy

Question 29

Define hydrocarbon.

Answer 29

A compound containing only hydrogen and carbon

Question 30

What is complete combustion?

Answer 30

When a fuel burns in excess oxygen

Question 31

What is incomplete combustion?

Answer 31

When a fuel burns in a limited supply of oxygen

Question 32

What are the products of incomplete combustion?

Answer 32

Carbon monoxide, soot, water

Question 33

What are the three sides of the fire triangle?

Answer 33

Heat, fuel, oxygen

Question 34

How can we extinguish any fire?

Answer 34

By removing one side of the fire triangle

Question 35

Which side of the fire triangle is removed by water?

Answer 35

Heat

Question 36

Why can’t water be used to extinguish an electrical fire?

Answer 36

It will cause electrocution

Question 37

How does a carbon dioxide fire extinguisher put out a fire?

Answer 37

CO2 is more dense than air so sinks and prevents oxygen getting to the fire

Question 38

If not extinguished, why do most fires eventually go out?

Answer 38

The fuel runs out

Question 39

What is a fire blanket?

Answer 39

A heavy blanket which prevents oxygen getting to the fire

Question 40

What are two uses of fire blankets?

Answer 40

When a person’s clothing is on fire, chip pan fires

Question 41

What is a fuel?

Answer 41

A material which burns to release energy

Question 42

What is a fossil fuel?

Answer 42

A fuel made of dead plants and animals that died and were buried millions of years ago

Question 43

Name the three fossil fuels.

Answer 43

Coal, oil, natural gas

Question 44

State two uses of fuels.

Answer 44

To keep us warm, for transport, to generate electricity

Question 45

In the fuel investigation, what is the independent variable?

Answer 45

Different fuels

Question 46

In the fuel investigation, what is the dependent variable?

Answer 46

Mass of fuel burned

Question 47

In the fuel investigation, identify two control variables.

Answer 47

Volume of water, increase in temperature

Question 48

How do we calculate how much energy is needed for a 1°C temperature rise?

Answer 48

Divide the mass of fuels burned by the temperature change

Question 49

What is thermal decomposition?

Answer 49

Substances are broken down by heat

Question 50

Why are thermal decomposition and combustion not the same?

Answer 50

Combustion involves oxygen, thermal decomposition does not

Question 51

What are the products of thermal decomposition of a metal carbonate?

Answer 51

Metal oxide and carbon dioxide

Question 52

What are the products of thermal decomposition of magnesium carbonate?

Answer 52

Magnesium oxide and carbon dioxide

Question 53

What makes a carbonate?

Answer 53

One carbon atom and three oxygen atoms

Question 54

What solution is used to test for carbon dioxide?

Answer 54

Limewater

Question 55

What is a positive test for the presence of carbon dioxide?

Answer 55

Limewater goes cloudy

Question 56

Give one use of thermal decomposition.

Answer 56

To produce lime for glass, cement, and limewater, as the first step in extracting copper from its ore

Question 57

What do we mean if we say that a metal carbonate is “thermally stable”?

Answer 57

Metal carbonates which will not break down when heated

Question 58

Without doing an experiment, how can we decide whether a metal carbonate will be thermally stable?

Answer 58

Thermally stable metal carbonates usually contain more reactive metals

Question 59

Why can’t all metal carbonates be thermally decomposed using a Bunsen burner?

Answer 59

Bunsen burner does not reach high enough temperatures

Question 60

Which metal carbonate changes colour when it thermally decomposes?

Answer 60

Copper carbonate

Question 61

Which metal oxide glows yellow when heated?

Answer 61

Zinc carbonate

Question 62

How do we test for carbon dioxide?

Answer 62

Limewater

Question 63

Write a word equation for the thermal decomposition of zinc carbonate.

Answer 63

Zinc carbonate 🡪 Zinc oxide + Carbon dioxide

Question 64

How do we know that thermal decomposition is an endothermic reaction?

Answer 64

Heat energy is taken in during the reaction

Question 65

Give an example of a physical change.

Answer 65

Ice melting, any change of state

Question 66

Give an example of a chemical change.

Answer 66

Combustion

Question 67

What is the law of conservation of mass?

Answer 67

Mass of the reactants equals the mass of the products, it cannot be lost or gained

Question 68

Who described the law of conservation of mass?

Answer 68

Lavoisier

Question 69

What seems to happen to the mass of a reaction if one of the reactants is a gas?

Answer 69

Increases

Question 70

What seems to happen to the mass of a reaction if one of the products is a gas?

Answer 70

Decreases

Question 71

Why should you not look directly at the magnesium ribbon during heating?

Answer 71

It burns with a bright white light

Question 72

What is the purpose of the balloon over the neck of the conical flask?

Answer 72

To capture the gas produced