# Floating and Sinking

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A series of free Science Lessons for 7th Grade and 8th Grade, KS3 and Checkpoint Science in preparation for GCSE and IGCSE Science.

Density - Float or sink?
Density is calculated by dividing the mass by the volume.
To find the mass of water you will need a beaker and a scale. First find the mass of the empty beaker. Next, fill up the beaker to your desired amount. Then use the scale to find the mass of the filled beaker. To find the mass of just the water, subtract the mass of the empty beaker from the full beaker. Our sample is 100 grams.
The volume of water can be measured using a graduated cylinder. Our sample is 100ml.
Density is calculated by dividing the mass by the volume. Plug in our measured mass at 100 grams and divide that by our measured volume of 100 ml. Water’s density is 1 g/ml.
Objects with a density greater than 1g/ml will sink when placed in water. Objects with a density less than one will float when placed in water.
Density explains why ice floats. If you freeze water, it expands. The black dots represent the atoms in water. No new atoms were are added to the water so because of the expansion there is more room between the atoms. Compared to the atoms in liquid water, the atoms in the ice are not as tightly packed together causing the ice to float. Try calculating density of ice for yourself. If you get a number less than one it will float.

Liquid Matter Density
Demonstrates density in liquids.

Density - Why does oil float on water?

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