The method and the results are on the heat and temperature lab. Do the analysis yourself first, then check the answers below.
Quick answer: Temperature measures how hot or cold an object is in degrees Celsius, while heat is thermal energy moving from a hotter object to a colder one. These answers go with the grade 7 science lab on heat and temperature: the graph, the calculations, the uncertainties and the conclusion explained, for all 8 analysis questions.
These model answers use the sample class results from the table. Also, your own numbers will differ, but cotton wool should beat the bare cup in the same way. Next, check your calculations and your explanations against the steps below.
Cup 1: 80 – 44 = 36 °C. cup 2: 80 – 54 = 26 °C. cup 3: 80 – 58 = 22 °C. cup 4: 80 – 51 = 29 °C. 36, 26, 22 and 29 °C.
Question 2 Rank the insulators
Smallest fall is best: cotton wool (22), newspaper (26), foil (29), bare (36). Also, cotton wool, newspaper, foil, none.
Question 3 Cooling rate
Cup 1: (80 – 66) ÷ 5 = 2.8 °C/min. cup 3: (80 – 73) ÷ 5 = 1.4 °C/min. 2.8 °C/min and 1.4 °C/min.
Question 4 Percentage improvement
(36 – 22) ÷ 36 = 0.389. About 39 %.
Question 5 Describe the graph
Cup 1 falls 14, 10, 7 and 5 °C in the four intervals. The fall decreases as the water gets closer to the room temperature, so there is less difference to drive heat flow. Moreover, the cooling slows down.
Question 6 Explain the best material
Cotton wool is full of tiny pockets of trapped air. The air conducts poorly and cannot circulate, so it reduces conduction and convection. In addition, trapped air is the reason.
Question 7 Foil and radiation
Shiny foil reflects some radiation back into the cup, so it loses less energy than a bare cup, but a thin foil layer traps little air and conducts well. Also, it reduces radiation but not conduction.
Question 8 Improve the lab
Repeat the test three times and calculate means, use the same thickness for each material and measure the water volume exactly. Then, repeat and control thickness.
