Mass, weight and gravitational force

Grade 6 Natural Sciences topic: “Mass, weight and gravitational force” (Unit 7 “Forces in action”, pp. 16–19, J. K. Randhawa, N. Mehta). Mass shows how much matter an object contains and is measured in kilograms (kg) and grams (g). Weight is a measure of the pull of gravity and is measured in newtons (N); the unit is named after Isaac Newton. Gravity is the force that pulls objects towards itself. On the Earth's surface a mass of 1 kg weighs 9.8 N. Gravity on the Moon is weaker than on Earth: an astronaut with a mass of 50 kg weighs 490 N on Earth and 82 N on the Moon. When gravity changes, weight changes but mass does not.