The method and the results are on the particle model lab. Do the analysis yourself first, then check the answers below.
Quick answer: The particle model says that all matter is made of tiny particles that are always moving. These answers go with the grade 7 science lab on particle model: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
These model answers use the sample class results from the table. Your own times will differ, but the pattern should be the same: higher temperature, shorter time. Compare your reasoning and calculations with the steps below.
The independent variable is the water temperature and the dependent variable is the time to spread evenly. Controls: the volume of water, the size of the drop and the cup type. Independent: temperature; dependent: time.
Question 2 Describe the pattern
The time falls from 540 s at 5 °C to 95 s at 60 °C. Higher temperature gives a shorter time.
Question 3 Compare the extremes
540 ÷ 95 = 5.68. About 5.7 times longer.
Question 4 Calculate the speeds
20 °C: 8.0 cm ÷ 300 s = 0.0267 cm/s. 40 °C: 8.0 cm ÷ 170 s = 0.0471 cm/s. 0.027 cm/s and 0.047 cm/s.
Question 5 Explain with particles
In warmer water the water particles move faster and collide with dye particles harder and more often, so the dye particles are carried around the cup sooner. Faster particles give faster diffusion.
Question 6 Judging the end point
Different people may decide the end point at different moments, and the dropper may swirl the water. Use the same person for all timings and a colour card to compare. A fixed end-point test reduces the uncertainty.
Question 7 Another source of error
The water in cup 4 cools while waiting, so it may be below 60 °C. The measured time would then be too long for 60 °C. Cooling makes hot-water times too long.
