Matter and Pressure

**Density**: The mass per unit volume of a substance. Calculated as mass / volume.
**Pressure**: The force acting perpendicular to a surface per unit area. Calculated as force / area.
Pressure increases with depth in a liquid due to the weight of the liquid above.
Gases also exert pressure, which increases with the number of gas particles in a given volume.
Pressure can be measured using a manometer or barometer.
Exam tip: Ensure you can calculate density and pressure using the relevant formulas and units.

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