KEY POINTS:
- Physical changes are accompanied by the release or absorption of energy. This has numerous everyday applications:
- Using an ice pack feels cooling because the ice absorbs heat energy from your skin as it changes from a solid to a liquid state.
- Sweating also feels cooling because the sweat absorbs heat energy from your body as it changes from a liquid to a gas state.
- Every type of substance has a different melting point and boiling point. This allows us to separate mixtures based on these differences, e.g. simple distillation and fractional distillation.
THINK OUTSIDE THE BOX:
- Can water shatter glass?
- Fractional distillation of liquid air is one source of pure oxygen. Is this cheaper than the decomposition of hydrogen peroxide? Research the costs involved to produce one kilogram of pure oxygen.