1. An imaginary line through the Earth which runs from pole to pole

2. The force that pulls towards the centre of Earth.

3. The planet where we live.

4. The path an object takes around another object in space. It takes a year for the Earth to do this around the sun, 28 days for the moon to do this around the Earth.

5. The Earth's natural satellite that revolves around it in about 28 days.

6. A shape like a ball.

7. A system of planets which revolve around...

1. Materials that will not dissolve, for example sand in water

2. Something that dissolves, salt and sugar are soluble in water.

3. Cannot be seen or out of sight.

4. Solid liquid and gas are states. So a change of state could be from solid to liquid - when ice melts and turns into water.

5. To change to another state: a gas or vapour turning into a liquid state.

6. The act of condensing; when steam hits a cold surface it changes state from a gas to a liquid an...

1. The size of a vibration or the height of the peaks and troughs of a wave.

2. This transmits vibrations from the outer ear to the small bones in the middle ear.

3. The number of times a wave vibrates in one second.

4. Materials which can prevent sound from travelling.

5. A device which can be used to show sounds as moving waves on a screen. The amplitude and frequency can then be measured.

6. How high or low a sound seems. Fast, high frequency vibrations give h

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