C1

• Describe the solid state of matter

  - Strong forces of attraction between particles that hold them in fixed positions in a regular lattice arrangement.

  - The particles do not move from their positions, so they keep a definite shape and volume.

  - The particles vibrate around fixed positions: changes in temperature affect the speed of these vibrations.

  
• Describe the liquid state of matter

  - There is some force of attraction between the particles, they are free to move past each other, but tend to stick together.

  - Liquids don't keep a definite shape, but do keep the same volume.

  - The particles are constantly moving with random motion: changes in temperature affect the speed of these vibrations.

  
• Describe the gas state of matter

  - There is next to no force of attraction between particles, they are free to move, travel in straight lines, and only interact after collisions.

  - Gases do not keep a definite shape or volume and will always fill a container. They always exert a pressure on the walls they collide with.

  - The particles move constantly with random motion: changes in temperature affect the speed of these vibrations.

  
• What is meant by a physical change?

  A physical change is a change, such as changes of state, that does not result in new substances being made. These types of changes are reversible.
• What is meant by a chemical change?

  A chemical change is a change that produces one or more new substances. These types of changes are hard to reverse.
• What happens to particles during changes?

  When a substance changes state, its particles stay the same but their arrangement and movement change.

  
• What are the limitations of the particle model?

  The particle model does not take into account:

  - The forces between particles

  - The size of particles

  - The space between particles
• What are atoms and molecules?

  - Atoms are the smallest particles of an element that still has its chemical properties.

  - A molecule is made from the two or more atoms joined together. They are joined by attractive forces called chemical bonds.
• What is inside an atom?

  - Protons and neutrons that are joined together as the nucleus at the centre of the atom.

  - Electrons that surround the nucleus in shells.

  
• What is the mass and charge of each subatomic particle?

  -Proton: Mass = 1

  Charge = +1

  
  

  -Neutron: Mass = 1

  Charge = 0

  
  

  -Electron: Mass = 0.0005

  Charge = -1
• What are isotopes?

  Isotopes of an element are atoms with the same number of protons and electrons, but a different number of neutrons.
• What are ions?

  Ions are charged particles. They are formed when atoms, or groups of atoms, lose or gain electrons.
• What did Dalton do?

  John Dalton suggested that all matter is made from atoms. he believed that atoms were tiny solid balls. His model explained:

  - all atoms of an element are identical

  - different elements contain different types of atom

  Due to the time period, technology was not advanced, this prevented Dalton from doing further research.

  
• What did Thomson do?

  J.J. Thomson discovered the electron during experiments that showed 'cathode rays' changed direction in electric and magnetic fields. Thomson's model of the atom had to make sense of two things:

  - atoms contain electrons

  - atoms are neutral overall

  His plum pudding model he suggested that atoms are spheres of positive charge with electrons dotted around inside.

  
• What did Rutherford do?

  He conducted the gold foil experiment with two of his students. In this experiment the:

  - fired positively charged alpha particles at an extremely thin sheet of gold.

  - they expected most of the particles to pass straight through or be slightly deflected at most, due to the positive 'pudding' of the atom.

  - however, they witnessed that although most passed through, some deflected more than expected, and some deflected straight back.

  - this proved J.J. Thomson's model incorrect.

  Instead, Rutherford came up with the nuclear atom, where there's a tiny positively charged nucleus in the centre of the atom surrounded by a 'cloud' of negative electrons.

  
• What did Bohr do?

  Bohr suggested that electrons can only exist in fixed orbits, or shells, and not anywhere in between. Each shell has a fixed energy.