Activity Use an electronic balance to find the mass of various objects, for example a pencil, a beaker, a bunch of keys. How could you use an electronic balance to find the mass of a
liquid?
Activity Mass of air: All matter has mass, including the air and other gases. It can be difficult to think of air as matter because we are able to move through it so easily. With this experiment, you will see that air does have mass.
Apparatus Two balloons, a metre stick, string, a needle
Method
1. 2. 3.
4. 5. 6.
Suspend a metre stick as shown in Fig. 4. Blow up two balloons to the same size. Tie a piece of string to each balloon and attach to opposite ends of the metre stick. Adjust the positions of the balloons on the metre stick to allow the stick to settle horizontally. After the metre stick has stabilised use the needle to poke a small hole in one balloon. (Be careful not to pop the balloon.) Observe what happens to the metre stick as the air leaks out of one balloon (Fig. 5)
Question How do these observations show that air has mass?
Fig. 4
Fig. 5
Science in Society Composition of air: We now know that air has mass. We also know that air is a mixture of different gases. Find out what are the main gases in air. A number of scientists were involved in discovering the composition of air. Most of these discoveries were made in the 1700s. Find out who these scientists were and what contribution each one made to our current understanding of air.
