In this topic we are learning to: z Define mass and volume. z Describe ways to measure the mass of different objects.
z Outline the correct use of a graduated cylinder and investigate how to measure the volume of regular- and irregular-shaped objects.
Measuring Mass Mass is the amount of matter in an object.
The SI unit for mass is the kilogram (kg). In the school laboratory, a lot of masses will be smaller quantities and are measured in grams (g). Some of the instruments that can be used for measuring mass are:
z Bathroom scales for measuring the mass of a person.
z An electronic mass balance for measuring the mass of a beaker of water.
z A spring balance for measuring the mass of an apple or a banana.
Fig. 15.3.1 A person on a bathroom scale
Fig. 15.3.2
A beaker of water on an electronic mass balance
Measuring Volume 15 cm
The volume of an object is the amount of space it takes up. The SI unit for volume is the cubic metre (m3). A lot of the volumes you come across in the laboratory will be smaller quantities and are measured in cubic centimetres (cm3).
30 cm 5 cm Fig. 15.3.4 A wooden block 264 264
Measuring volume depends on the shape and size of the object being measured.
z If you want to measure the volume of a regular shape – such as a wooden block or a cylinder – use a ruler to measure its dimensions. The volume of the block in Fig. 15.3.4 can be calculated using the following formula.
Volume = length x breadth x height Volume = 30 x 5 x 15 = 2,250 cm3
