An interesting question came out of our review of IGCSE exam papers this week – how much does a metre ruler weigh? Actually, we really want to know its mass as weight and mass are different in physics. It turns out that estimating the mass of things is an important (and examinable) skill. You can estimate the mass of a lot of common objects by remembering that 1 mL of water has a mass of 1 gram. So a 1 litre carton of milk has a mass of 1 kilogram. Practise estimating the mass of everyday objects.
