Physical & Chemical Changes
Physical change
- Physical changes (such as melting or evaporating) do not produce any new chemical substances
- These changes are often easy to reverse
- Making a mixture from 2 or more substances or dissolving a solute in a solvent are examples of physical changes as no new substances are produced and are usually relatively easy to separate
Chemical change
- During chemical changes (usually referred to as chemical reactions), new chemical substances are formed that have very different properties to the reactants
- There may be signs that a new substance has formed, such as:
- A colour change
- A precipitate being formed
- Bubbles of gas being produced
- Most chemical reactions are very difficult to reverse
- Energy changes also accompany chemical changes and energy can be given out (exothermic) or taken in (endothermic)
- The majority of chemical reactions are exothermic with only a small number being endothermic
