LSCPHYS1: Meaning of density Assignment

Assignment One

Look at the objects in Figure 2.19. Which is the biggest and which is the heaviest? Do you agree with your friend? Why may the biggest not be the heaviest?

Do we mean: Which object has the greatest mass? Which object has the most matter in it?

Or do we mean: Which object has the greatest volume? Which object takes up the greatest amount of space?

Assignment two

Predict, observe and explain

Take a used ballpoint pen top. It is made out of polythene. It has a density of about 0.9 g cm-3. Will it float in water? Predict what will happen if you put it in some methylated spirit (density 0.8 g cm-3). Try it to find out if your prediction is correct. What do you observe? Explain your observation.

Assignement Three

Predict, observe, and explain

Take two empty cold drinking cans. Crush one as small as you can by stamping on it. Put both cans in a bucket of water.

1. Predict what will
2. Observe what
3. Explain your

Assignment Four

Predict, observe and explain

Put a fresh egg in a beaker of water. What happens?

Predict what will happen if you add salt to the water and stir (don’t break the egg!).

Add salt and stir and observe what happens.

Explain your observation.

Assignment Five

1. Explain what we mean by the statement ‘density of a substance is 1 g cm3 ‘
2. a) Explain why a copper coin sinks when put in
3. b) A log of wood has more mass than a copper coin, but it does not sink in Explain why.
4. The density of a metal is 9 g cm-3. What does it mean? What is the importance of this value?
5. A rectangular piece of glass has a mass of 8 g and measures 2 cm by 9 cm by 3 cm. Find its density and express your answer in kg m-3.
6. 200 cm3 of a liquid of density 7 g m-3 is mixed with 100 cm-3 of liquid of density 0.9 g m-3. Assuming there was no loss of liquid during mixing and there was uniform mixing, find the density of the mixture.