Chemical Reactions page 86-98

Question 1

What are chemical reactions?

Answer 1

A chemical reaction is a change in which atoms rearranged to create new substances. The atoms are joined together in one way before the reaction and in a different way after the reaction.

Question 2

What do all chemical reactions do?

Answer 2

They make new substances.

They transfer energy to or from the surroundings.

Question 3

What things might you notice to determine if it is a chemical reaction?

Answer 3

You might see huge flames or tiny sparks.
You might notice a sweet smell or a foul stink.
You might feel the chemicals getting hotter or colder. You might hear a loud bang or gentle fizzing.

( you don’t need to memorise all of this at least know two )

Question 4

What useful substances do chemical reactions form?

Answer 4

They form medicines such as paracetamol.
They form fabrics such as polyester.
They from building materials such as cement.

Question 5

What type chemical reaction is not useful?

Answer 5

Rusting is not useful it can damage cars, boats and bridges.

Question 6

What do chemists use catalysts for?

Answer 6

They use them to speed up a slow reaction.

Question 7

What is a physical change?

Answer 7

A change that is reversible, in which new substances are not made.

Question 8

What are some examples of physical changes?

Answer 8

Examples of physical changes include changes of state, and dissolving.

Question 9

What two elements react to make carbon dioxide?

Answer 9

Carbon and oxygen react to make carbon dioxide.

Question 10

What does carbon dioxide from as?

Answer 10

It forms as an invisible gas.

Question 11

What happens if you heat iron fillings and sulphur powder?

Answer 11

The mixture glows red, a new substance forms.

Question 12

What are reactants?

Answer 12

Reactants are the starting substances in chemical reaction.

Question 13

What are products?

Answer 13

The substances made in the reactions are called products.

Question 14

What are hazards?

Answer 14

Hazards are possible sources of danger.

Question 15

What are risks?

Answer 15

Risks are the chances of damage or injury from hazards.

Question 16

What does the arrow in a word equation?

Answer 16

The arrow in a word equation means reacts to make.

Question 17

What is a fuel?

Answer 17

A fuel is material that burns to transfer energy by heating.

Question 18

What are some examples of a fuel?

Answer 18

Fuel include petrol, diesel, coal, hydrogen and waste cooking oil.

Question 19

What is burning also called?

Answer 19

Burning is also called combustion.

Question 20

What is methane a compound of?

Answer 20

Methane is a compound of carbon and hydrogen.

Question 21

What is a fossil fuel?

Answer 21

A fuel made from the remains of animals and plants that died millions of years ago.

Question 22

What do fossil fuels include?

Answer 22

They include coal, oil and natural gas.

Question 23

What does non-renewable mean?

Answer 23

Non-renewable means that they cannot be replaced once they have been used, they will run out one day.

Question 24

What are oxidation reactions?

Answer 24

Burning reactions are oxidation reactions.

Question 25

When oxygen reacts with other substances what type of reaction is this known as?

Answer 25

An oxidation reaction.

Question 26

What happens in decomposition reactions?

Answer 26

In decomposition reactions, a compound breaks down onto simpler elements or compounds.

Question 27

What is a thermal decomposition reaction?

Answer 27

When a substance breaks down on heating, the reaction is a thermal decomposition reaction.

Question 28

What is a discrete variable?

Answer 28

A discrete variable is described by words, or by numbers that can only have certain values, such as shoe sizes.

Question 29

What is conservation of mass?

Answer 29

In any chemical reaction, the total mass of reactants is equal to the total mass of products. This is called conservation of mass. Mass is also conserved in physical changes.

Question 30

What do balanced symbol equations show?

Answer 30

The formulae of reactants and products
How the atoms are rearranged
The relative amounts of reactants and products.

Question 31

What is an endothermic change?

Answer 31

Melting and boiling reactions are endothermic changes.

Question 32

What is an exothermic change?

Answer 32

All burning reactions are exothermic.