C3: Chemical Reactions

Question 1

All chemical reacitons do what 2 things?

Answer 1

1. Make new substances
2. Transfer energy to or from the surroundings.

Question 2

What is a chemical reaction?

Answer 2

Where atoms are rearranged to make new substance.

Question 3

Most chemical reactions are not easily reversible. What does this mean?

Answer 3

At the end of a reaction it is very hard to get back what you started with.

Question 4

When an ice cube melts is this a chemical reaciton or a physical change? Why?

Answer 4

Physical change

because it can be reversed e.g. changes of state can be reversed.

Question 5

What is a catalyst?

Answer 5

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

They are not used up in the reaction.

Question 6

What sort of things might you oberserve when a chemical reaction is happening?

Answer 6

Fizzing/Bangs

Smells

Temperature changes

Colour changes

Question 7

When are chemical reactions not so useful?

Answer 7

Rusting is a chemical reaction.

This damages cars, boats and bridges.

Question 8

The particles that make up all matter are called…

Answer 8

atoms

Question 9

Is a physical change a chemical reaction?

Answer 9

No because it is reversible e.g. melting chocolate.

Question 10

Chemical reactions are useful for making substances such as:

Answer 10

Medicines - paracetamol

Fabrics - polyester

Building materials - cement