Calculating density Calculate the density of a bar of milk chocolate. Would the density of one square of that bar be higher/lower/the same? Repeat the activity using dark chocolate. Discuss your findings.
To find the density of a stone Density =
= =
Mass = 42 g Volume = 12 cm3 Fig. 3 Finding the density of a stone.
To find the density of a liquid Place an empty beaker on the electronic balance. Zero the balance. Place a known volume of the liquid into the beaker, using a pipette or graduated cylinder. Record the mass of the liquid. Use the formula Density =
1. 2. 3. 4. 5.
Mass Volume to find the density.
Floating or sinking An object floats because its density is less than the density of the liquid it is in. If its density is more than the liquid’s density, it sinks. Therefore, an object that floats on water (e.g. a cork, or a drop of oil) must have a density of less than 1 g cm-3
, which is the density of water. Activity
1. 2. 3. 4.
Observing the densities of different liquids Get a boiling tube and fill one third with golden syrup. Pour in a similar volume of water and then oil. Note how the three liquids are arranged. In another tube repeat the exercise but this time reverse the order in which you add the liquids. What do you observe this time?
307 An object
floats because its density is less than the density of the liquid
