The method and the results are on the weight and mass lab. Do the analysis yourself first, then check the answers below.
Quick answer: Mass is the amount of matter in an object, measured in kilograms, and it never changes. These answers go with the grade 7 science lab on weight and mass: the graph, the calculations, the uncertainties and the conclusion explained, for all 8 analysis questions.
These model answers use the sample table. Your own readings will differ slightly, but the graph should be a straight line through the origin with a gradient close to 9.8 N/kg.
Level: Grade 7 science (Year 8 · Class 7) · Curriculum: MS-PS2-4
Question 1 Quantities in the lab
You change the mass on the hanger and you measure the weight shown by the pointer. The same spring scale and the same location (so g does not change) stay fixed.
Question 2 Expected weights
W = m × 9.8: 0.050 → 0.49 N; 0.100 → 0.98 N; 0.150 → 1.47 N; 0.200 → 1.96 N; 0.250 → 2.45 N; 0.300 → 2.94 N.
Question 3 Draw the graph
The points lie on a straight line through the origin, which shows that weight is directly proportional to mass.
Question 4 Gradient
Gradient = 2.9 ÷ 0.300 = 9.7 N/kg (9.67).
The gradient equals the gravitational field strength g at the place of the experiment.
Question 5 Percentage difference
Difference = (9.8 − 9.67) ÷ 9.8 × 100 = 1.4 %. The result is very close to the accepted value.
Question 6 Prediction
W = 0.450 × 9.8 = 4.41 N, about 4.4 N.
This is close to the 5 N maximum, so a slightly larger load could overstretch the spring.
Question 7 On the Moon
The line would still pass through the origin but be much shallower, with a gradient of 1.6 N/kg.
Reading = 0.300 × 1.6 = 0.48 N.
Question 8 Zero error
All readings would be 0.1 N too high, so the line would cross the y-axis at 0.1 N instead of passing through the origin. Subtract 0.1 N from every reading or adjust the zero screw before starting.
