Chemistry.

Chemistry.

Chemical reactions
1. A new substance is ALWAYS formed
  1. there are reversible and irreversible.
2. You can tell as sometimes there is a colour when gas is given off.
Physical changes.
1. No new substance.
2. Melting
  1. evapuration
3. Normally reversable
they give of energy changes/ give off energy
1. usually from heat also can envolve light and sound
some react with metals
1. and carbon dioxide is given off
we use equations for this xx
for fire we need heat
1. fuel
2. oxegon
3. if any of this is taken away the fir will go out that how we use fire extingwishers.
  1. explosions are short but powerful reactions
    1. this is mainly when chemicals have oxegon and need to react.
4. there are different types per fire.
  1. water is main but we use co2 blankets and sand as well to smother the fire.
    1. never use water on petrol/oil fires
  2. fuel+oxegon = carbon dioxide + water

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	Criado por elliemaiangel quase 11 anos atrás