Metals can be ranked in order of reactivity, by reacting them with Air, Water or Acid. 

Alkali metals; Lithium, Sodium and Potassium need to be stored and used safely.

·   They are store in oil to prevent them from reacting with Oxygen and moisture (water) in the air.

·   Tweezers are used to hold them in case they react with moisture on the skin.

·   A safety screen is used when reacting them with water.

·   Goggles must always be worn

All sounds are produced by vibrations.

Sound can travel through different materials at different speeds.

Sound can travel faster in a liquid than in air. Sound travels even faster in a solid because the particles are closer together and can ‘bump’ into each other much easier.

Sound cannot travel through a vacuum. This is because there are no molecules to pass on the vibrations.

Sound travels at about 330m/s in air, but can travel faster in liquids and solids.

Light travels faster than sound at 300,000,000 m/s in air.

The loudness of a sound is related to the amplitude of the vibration. The loudness of a sound is measured in decibels (dB). Your ear is easily damaged by loud sounds—this can lead to loss of hearing due to damage to the ear drum.

The pitch of a sound is related to the frequency of the vibration causing the sound. The rumbling of thunder has a low pitch sound and low frequency. A high pitch sound has a high frequency, like a whistle. 

The frequency is measured in hertz (Hz). The range of frequencies that can be heard varies from person to person (from about 20Hz up to 20,000Hz).