Physical Changes
Physical changes do not change the chemical identity of the substance.
Do not confuse this with changing the phase of a substance.
When water melts, its chemical identity is still H₂O, so melting is a physical change. Phase changes are physical changes. You can do anything to the phase of water, but as long as it remains H₂O, it is a physical change.
Examples of physical changes are phase changes, bending, cutting, breaking, and dissolving.
Chemical Changes
Chemical changes do change the chemical identity of the substance. The idea is that once you perform a chemical change, you cannot easily reverse said change because a new substance is formed.
For example, when you are baking a cake, you use flour, sugar, and other ingredients to make the cake. However, from that cake, you cannot get the flour and sugar back.
Other examples include lighting wood on fire (turns into ash) and iron reacting with water to form rust.
There are indicators of chemical change ↴
– Color change
– Temperature change
– Precipitate forms (a solid that is formed in a liquid)
– Gas produced (bubbles form)
– Odor production
– Light is produced
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