1st half term grade test

1. States of matter
   1. Solid

      Anotações:

      • Particles are close together in a regular arrangement
      • The attraction between particles are strong.
      • The particles vibrate around a fixed position; a solid has a fixed shape.
      • The volume does not change because the particles cannot move closer together.
   2. Liquid

      Anotações:

      • Particles are still close together (most touching) but are arranged irregularly
      • The force of attraction between particles is less strong than a solid.
      • The particles move around and slide past each other; liquids can be poured.
      • Under pressure the volume does not change because the particles cannot move closer together.
   3. Gas

      Anotações:

      • Particles are far apart, arrangement is random.
      • The force of attraction between particles is very weak.
      • The particles move freely and at speed, they collide with each other and bounce away randomly; gasses spread.
      • Under pressure the gas is pushed into a smaller volume because the particles can move a lot closer together.
2. Diffusion

   Anotações:

   • Difussion is where particles mix and spread throughout the space, evening the concentration out until they are the same.
   1. Speed of diffusion

      Anotações:

      • The smaller the relative molecular mass, the more quickly particles diffuse.
      • Diffusion is also faster when - A. It is hotter, the particles move faster as they have more energy B. It is in gas as the speed of  gas particles is faster.
3. Changing state

   Anotações:

   • On heating particles gain energy and move faster; they change state when they gain enough energy to overcome the forces of attraction.
   • On cooling, the particles lose energy and move more slowly; as they get closer the forces of attraction take over and change state.

Anotações:

• When a substance is pure then the temp remains the same during a change of state (I.e. horizontal part of graph)
• During boiling the energy breaks these attractions futher
• During melting the energy- heat, is being used to break some of the attractions between particles.
• In between state changes the particles are vibrating and moving more as the energy is taken in and the temp rises.

1. Heating curve
2. Cooling curve

Anotações:

• By measuring the melting and boiling points you can tell if pure. You can identify pure substance by measuring melting and boiling point.

1. Pure

   Anotações:

   • Has no particles of any other substance mixed in with it. Melts and boils at unique temp. Melts sharply at melting pt
2. Impure

   Anotações:

   • Has other particles mixed in Melts over range temp not sharply. Melt lower temp Boil higher temp

1. Element

   Anotações:

   • Pure substance containing only one type of atom e.g. oxygen
2. Compound

   Anotações:

   • A pure substance containing 2 or more types of atom chemically bondede.g. CH4
3. Mixture

   Anotações:

   • 2 or more substances which are not chemically bonded and can easily be seperated by phisical process. E.g. air