6.4 Chemical Reactions

Question 1

What is matter made up of?

Answer 1

Particles

Question 2

What are the smallest particles called?

Answer 2

Atoms

Question 3

What are atoms?

Answer 3

The smallest building blocks from which all substances are made

Question 4

What shape are atoms?

Answer 4

They are hard spheres

Question 5

What do atoms usually form?

Answer 5

They are rarely on their own and they cluster together to form molecules

Question 6

What are The 5 principles of Daltons atomic theory of matter?

Answer 6

1) all matter is made up of tiny, hard, invisible particles called atoms
2) substances made up of one type of atom are called elements
3) the atoms of different elements can be distinguished by their different masses
4) atoms can combine to form new substances called molecules
5) atoms are not created or destroyed in a chemical change

Question 7

In a pure substance, what are molecules like?

Answer 7

Molecules all have the same number of atoms and are identical in size and shape

Question 8

When a chemical change occurs, what happens to the atoms?

Answer 8

They rearrange to form different combinations of atoms

Question 9

What happens if atoms rearrange to form a new substance with a different colour?

Answer 9

A permanent colour change has occurred

Question 10

What happens if atoms rearrange to form a gas?

Answer 10

You will see bubbles, smoke or smell new odour

Question 11

What happens if atoms rearrange to form a solid?

Answer 11

A precipitate may occur

Question 12

In a chemical change can the atoms be created or destroyed?

Answer 12

No they are never created or destroyed

Question 13

What are the starting substances known as in a chemical reaction?

Answer 13

Reactants

Question 14

What are the substances that are formed in chemical reactions.

Answer 14

Products

Question 15

What do reactants rearrange to form?

Answer 15

Products

Question 16

How are atoms in molecules and lattices held together?

Answer 16

They are held together by chemical bonds that store energy

Question 17

What are spontaneous reactions?

Answer 17

They are reactions that proceed by themselves

Question 18

What are the two types of spontaneous reactions?

Answer 18

First can obtain enough energy from the surroundings to start and continue
The other needs a kick start from an external energy supply but can then continue with the reaction

Question 19

What are non-spontaneous reactions?

Answer 19

Require and energy to be constantly added to it otherwise the reaction will stop

Question 20

Why do scientists use chemical equations?

Answer 20

Because it is clearer, faster and easier

Question 21

What replaces an equal sign in a reaction?

Answer 21

An arrow, there is no equal sign. The arrow means that the reactants have become the products

Question 22

What s the simplest was to write a chemical equation?

Answer 22

By using chemical names:
Hydrochloric acid (HCL) + Sodium Chloride (NaOH)
A word equation looks like this:
Hydrochloric acid + Sodium Hydroxide -> Sodium Chloride + Water

Question 23

What is a chemical equations?

Answer 23

Chemical name is now resolved with chemical formula

HCl + NaOH -> NaCl + H2O

Question 24

What is corrosion?

Answer 24

When metal reacts with oxygen

Most common type of corrosion is rust

Question 25

What makes some metals more likely to corrode?

Answer 25

Their chemical properties

Question 26

What is rusting?

Answer 26

The name giving to the corrosion of iron

Iron needs to react with oxygen or water to produce orange-brown compound iron (iii) oxide (Fe2O3)

Question 27

How can you prevent rusting?

Answer 27

Coating, galvanising and alloying

Question 28

Why do we using costing?

Answer 28

It is cheapest and simplest way to protect iron

Coating forms a barrier between iron and oxygen

Question 29

What happens if the barrier is removed in coating?

Answer 29

If coating is scratched or cracked the the barrier is removed and rusting will occur

Question 30

What do we use to coat iron?

Answer 30

Paint, plastic or other metals like chromium

Question 31

What is galvanising?

Answer 31

If iron is coated with zinc, it is good because even if it is scratched or cracked it will still protect

Question 32

What does zinc react easily with?

Answer 32

Oxygen but even when it is scratched, the zinc reacts with oxygen not iron

Question 33

What is iron is mixed with other metals?

Answer 33

The chemical and physical properties change. These mixtures are known as alloys

Question 34

Why is iron never used in its pure form?

Answer 34

Because it is too soft and undergoes corrosion quickly

Question 35

What is stainless steel made up of?

Answer 35

90% iron

10% chromium