Chapter 1: Energy
• Lead a discussion on how the experiment has suggested that different substances will increase in temperature by different amounts when they gain the same amount of heat, or that different substances require different amounts of energy in order to increase in temperature by the same amount.
• Discuss that this is because different substances have different specific heat capacities. Use questioning to get students to come up with a definition and an equation. Some classes will need to be led far more than others. Note: students will always be given this equation in examinations, so they do not need to recall it.
• Give some typical values of specific heat capacity, for example, cwater = 4200 J/(kg °C), cdry soil = 800 J/(kg °C), csand = 290 J/(kg °C), ccopper = 385 J/(kg °C). Note: one calorie is the amount of energy that causes 1 g of water to increase in temperature from 14.5 °C to 15.5 °C. Substances actually have different specific heat capacities at different temperatures, but this is beyond the syllabus. [O1, O2, O3]
Explain • Challenge students’ thinking and understanding of heating water and soil from the practical activities using the evaluation section of Practical sheet 1.5. [O1, O2]
Consolidate and apply • The students should then be issued with the Specific heat capacity worksheet appropriate to their ability: • Low demand: Worksheet 1.5.1 • Standard demand: Worksheet 1.5.2 • High demand: Worksheet 1.5.3 [O1, O2, O3] Extend • Each student or student pair suggests how life would be different if water and land had similar specific heat capacities. [O1, O2]
Plenary suggestions Ask me a question: Ask the students to write a question about something from the lesson and then a mark scheme for the answer. Encourage them to come up with questions worth more than one or two marks and try out their questions on one another. Where’s the answer? As students enter the room, give them a card with a word written on it. At the end of the lesson, ask a question related to the lesson. Ask them if they think their card contains the answer and why. [O1, O2, O3]
Answers to questions Worksheet 1.1-1.3 (1.5.1 – a, d, e, f and g; 1.5.2 – a–h; 1.5.3 – a–i) a) The specific heat capacity of a substance is the amount of energy required to raise the temperature of b) c) d)
one kilogram of the substance by one degree Celsius. J/(kg °C) ∆E = mc∆θ
e)
f) g) h) i)
Specific heat capacity of water is much greater than that of land. Therefore it is much more difficult to alter the temperature of water, compared with that of sand (increase and decrease). 790 J/(kg °C) 6 °C 50 kg 87 000 J
Practical sheet evaluation 1. any sensible answer that correctly connects the hypothesis to the findings, looking at lines on graph 2. The data for both soil and water were on the same graph so that they could be compared easily. 3. In the day, land heats up faster than water. 4. At night, land cools down faster than water. AQA GCSE Physics: Teacher Pack
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