C1.1 The Particle Model

Question 1

What is a particle?

Answer 1

A tiny bit of matter

Question 2

What is the particle model?

Answer 2

The particle model describe how particles are arranged and how they move in solids, liquids and gases.

Question 3

Describe the particles in a liquid

Answer 3

There are some forces of attraction between the particles.
They’re free to move past each other.
Liquids don’t keep a definite shape and will flow to fill the bottom of a container but they do keep the same volume.
The particles are constantly moving with random motion.
Random arrangement of particles

Question 4

Describe the particles in a gas

Answer 4

There forces of attraction between the particles are extremely weak.
They travel in straight lines and only interact when they collide.
Gases don’t keep a definite shape or volume and will always fill any container. When particles bounce off the walls of a container, they exert a pressure on the walls.
The particles move constantly with random motion.

Question 5

Why can’t you compress a substance in its solid state or its liquid state?

Answer 5

This is because there is no space for the particles to move into

Question 6

Why can’t a substance in the solid state flow?

Answer 6

This is because the particles do rate around fixed positions and cannot move from place to place

Question 7

What is meant by the term ‘physical change’?

Answer 7

A physical change happens when a substance changes state or shape, or breaks into pieces.
No new substances are made.
Many physical changes can be reversed

Question 8

What is the relative mass of a neutron

Answer 8

1

Question 9

Give examples of physical change.

Answer 9

Freezing water
Mixing sand with water
Dissolving sugar in water

Question 10

What is meant by the term ‘chemical change’?

Answer 10

A chemical change is a change that produces one or more new substances.
The properties of the new substances are often very different from the properties of the original substance.

Question 11

Give examples of chemical change

Answer 11

Baking a cake
Steel rusting
An acid reacting with an alkali to make a salt and water

Question 13

What happens to the particles during a chemical change?

Answer 13

The particles break up and then join together in different ways

Question 14

What is the relative mass for a proton

Answer 14

1

Question 15

Define the term ‘atom’.

Answer 15

An atom is the smallest particle of an element that still has its chemical properties.

Question 15

What is the equation to work out the space between atoms?

Answer 15

Ratio of distance = distance between atoms / diameter of atom
to diameter

Question 16

Define electrostatic forces

Answer 16

These are the forces between positive and negative charges.
The forces become weaker the further apart the particles are
They are the strongest in solids and the weakest in gases

Question 19

JJ Thompson

What was his atomic theory?

Answer 19

He discovered the first subatomic particle (the electron), in 1897.
Atoms contain electrons
Atoms are neutral overall
Plum pudding model- Thomson suggests that atoms are spheres of positive charge with electrons dotted around inside, like pieces of fruit in a cake.

Question 20

Define the term ‘molecule’

Answer 20

A molecules is made from two or more atoms joined together

Question 21

What is the typical value for atomic radius?

Answer 21

10^-10m

Question 22

How is the bond length measured?

Answer 22

Centre point of one atom to the other centre point of the other atom

Question 22

What is the relative mass for electron?

Answer 22

0.0005

Question 24

Define the term ‘ions’

Answer 24

Ions are charged particles that are framed when atoms lose or gain electrons to obtain a full outer shell

Question 25

Ernest Rutherford

What was his atomic theory?

Answer 25

He conducted the gold foil experiment with Hans Geiger and Ernest Masden. They fired positively charged alpha particles at an extremely thin sheet of gold. They were expecting the particles to pass straight through the sheet or be slightly deflected. However, some were deflected more than expected.
Rutherford came up with the theory that an atom has a positively charged nucleus containing most of its mass. He also suggested that outside the nucleus, electrons orbit like planets in a solar system.

Question 26

John Dalton

What was his atomic theory?

Answer 26

All atoms of an element are identical
Different elements contain different types of atom.
He thought of atoms as tiny solid balls.

Question 27

What happens to the particles during a physical change?

Answer 27

It’s particles stay the same but their arrangement and movement change

Question 28

Niels Bohr

Answer 28

He realised that orbiting electrons would be attracted to the oppositely charged nucleus and would rapidly spin inwards. He showed that electrons occupy fixed energy levels, or shells, around the nucleus.

Question 29

Describe the particles in solids.

Answer 29

There are strong forces of attraction between particles, which hold them in fixed positions in a very regular lattice arrangement.
The particles don’t move from their positions so all solids keep a definite shape and volume and don’t flow like liquids.
The particles vibrate about their position

Question 29

What are the limitations of the particle model?

Answer 29

It does not take in account:

• the forces between particles
• the size of particles
• the space between particles

Question 29

Define the term ‘isotopes’

Answer 29

Isotopes of an element are atoms with the same number of protons and electrons but different number of neutrons.
So they have the same atomic number but different mass number