C1.1 The Particle Model Flashcards
What is a particle?
A tiny bit of matter
What is the particle model?
The particle model describe how particles are arranged and how they move in solids, liquids and gases.
Describe the particles in a liquid
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
Describe the particles in a gas
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.
Why can’t you compress a substance in its solid state or its liquid state?
This is because there is no space for the particles to move into
Why can’t a substance in the solid state flow?
This is because the particles do rate around fixed positions and cannot move from place to place
What is meant by the term ‘physical change’?
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
What is the relative mass of a neutron
1
Give examples of physical change.
Freezing water
Mixing sand with water
Dissolving sugar in water
What is meant by the term ‘chemical change’?
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.
Give examples of chemical change
Baking a cake
Steel rusting
An acid reacting with an alkali to make a salt and water
What happens to the particles during a chemical change?
The particles break up and then join together in different ways
What is the relative mass for a proton
1
Define the term ‘atom’.
An atom is the smallest particle of an element that still has its chemical properties.
What is the equation to work out the space between atoms?
Ratio of distance = distance between atoms / diameter of atom
to diameter
Define electrostatic forces
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
JJ Thompson
What was his atomic theory?
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.
Define the term ‘molecule’
A molecules is made from two or more atoms joined together
What is the typical value for atomic radius?
10^-10m
How is the bond length measured?
Centre point of one atom to the other centre point of the other atom
What is the relative mass for electron?
0.0005
Define the term ‘ions’
Ions are charged particles that are framed when atoms lose or gain electrons to obtain a full outer shell
Ernest Rutherford
What was his atomic theory?
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.
John Dalton
What was his atomic theory?
All atoms of an element are identical
Different elements contain different types of atom.
He thought of atoms as tiny solid balls.
What happens to the particles during a physical change?
It’s particles stay the same but their arrangement and movement change
Niels Bohr
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.
Describe the particles in solids.
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
What are the limitations of the particle model?
It does not take in account:
- the forces between particles
- the size of particles
- the space between particles
Define the term ‘isotopes’
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
