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Grade: 8
Subject: Physics
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Date:
Topic: Density Notes
Mass is the amount of matter in an object. It is measured using a digital balance, beam balance. SI unit is kg
Volume is the amount of space that matter occupies. Vol of a cuboid = l x b x h, Vol of a cube= side3.
SI unit is m3. Vol of a liquid is measured using a measuring cylinder.
Density is defined as mass per unit volume.
SI unit of volume is kg/m3
Buoyancy- The ability or tendency of something to float in water or some other liquid.
Effect of pressure and temperature on density
 As pressure increases density increases and as temp increases, density decreases.
 The densities of gases are compared by measuring them at the same temperature and pressure.
This is called the standard temp and pressure. The standard temp is 0°C and pressure of 760 mm.
How does a hot air balloon work?
Hot air rises up because it is less dense than cold air. As the air inside the balloon is hotter than the air
surrounding the balloon it rises up.
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