Chemical and Physical Changes
Physical changes are a change of state.
During a physical change, no new substances are produced.
You are simply changing the state of the substance.
Physical changes are easy to reverse.
Chemical changes involve a chemical reaction where new substances are made.
A chemical reaction is the formation of a new substance from two or more other substances. This causes a chemical change in the substance.
A change in the colour, light being given off, fizzing, smoke or a gas being released, heat being given out or being taken in are good indicators that a chemical change has taken place.
The products of a chemical change do not have the same chemical and physical properties as the substances they were made from. In other words, they may have changed colour and/or state.
Chemical changes are not easy to reverse.
Not all things are as simple they seem though.
Burning a candle is both a chemical and physical
The physical change is the wax melting from the
heat of the flame.
The chemical change is from burning some of
the wax when the candle is lit.
Copper Sulphate: when its hydrated is blue – its chemical
formula is CuSO4.5H2O. Which means that for every
molecule of copper sulphate there are 5 molecules of water attached.
When you heat copper sulphate you are removing the water – you should see condensation on the side of the test tube and steam escaping from the top. The copper sulphate also turns white.
THIS IS A PHYSICAL CHANGE.
When water is added, the copper sulphate turns blue again.
THIS IS A CHEMICAL CHANGE.