Q1.
Fill one cup half with water and mark it as ‘A’, second with sand and mark it as ‘B’, and the third with pebbles and mark it as ‘C’. Predict which one would be heavier and which one would be lighter? Weigh each cup using a balance and record the readings in your notebook. Compare the data and infer which is heavier or lighter.
Answer
Method: take three identical paper cups so that the cup itself adds the same amount every time, and fill each exactly half — so all three hold the same volume. Weigh each on a balance and note the reading.
| Cup | Filled with | Prediction | Typical reading | Inference |
|---|---|---|---|---|
| A | Water | Lightest | about 50 g | Least mass |
| B | Sand | Heavier than water | about 75 g | More mass |
| C | Pebbles | Heaviest | about 80 g | Most mass |
Inference: C (pebbles) is the heaviest and A (water) is the lightest, even though all three cups hold the same amount. Your own readings will differ with the size of your cup — write down what your balance actually shows.
Same volume in each cup
Heavier cup → more mass
Lighter cup → less mass
Units of mass: gram (g) and kilogram (kg)
Heavier cup → more mass
Lighter cup → less mass
Units of mass: gram (g) and kilogram (kg)
Why the comparison is fair only when the volumes are equal: a full cup of water is of course heavier than a spoonful of pebbles. The activity fills every cup half so that the only difference left is the material. Mass is the property that tells us how heavy or light an object is.
Tip: If your pebbles are large, big air gaps are left between them and cup C may weigh about the same as cup B. Try again with smaller pebbles that pack closely — and record the honest result either way. In common language we say ‘weight’ for mass because we find it by weighing; the difference between mass and weight is studied in higher classes.