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So taking a bite….this happens…..which ingredient has caused the problem and why?. P1 1.7 Specific heat capacities. Learning Objectives Explain what specific heat capacity is. Use the equation for specific heat capacity. - PowerPoint PPT Presentation
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P1 1.7 Specific heat capacities.
Learning Objectives
• Explain what specific heat capacity is.
• Use the equation for specific heat capacity.
• Evaluate the use of materials according to their specific heat capacities.
• If you give the same amount of heat to different type of matters you observe that changes in their temperatures are different.
• Given an equal amount of heat to metal spoons and wooden spoons, metal spoon has greater change in its temperature.
• These examples show that each matter has its own characteristics to absorb heat.
• We call this concept as specific heat capacity of the matters.
• It is the distinguishing property of matters. • We show it with the letter “c” and give the definition of
it as, heat required to increase temperature of unit mass 1 ºC.
• On the contrary, heat capacity of the system is defined as “heat required increasing the temperature of whole substance” and we show it with “C”.
• E=m.c where m is the mass of the substance and c is the specific heat of the matter.
The specific heat capacity equation.
• E = m c Δ T
Where
• E is the energy in Joules
• m is the mass of the material in kg
• c is the specific heat capacity of the material (this will be given to you)
• Δ T is the change in temperature °C
Exam feedback ….in an exam you will be expected to be able to re-arrange equations and put the quantity you need to calculate on the left.
How much energy does a kettle transfer when it heats up 1 kg of water from 10˚c to100 ˚c?
The specific heat capacity of water is 4200J/kg ˚c
E = m x c x
Heat mass specific heat temp change
Transferred capacity
378kJ = 1kg x 4200 x 90
Questions
1. A student heats 1kg block of aluminium and a 1kg block of copper to 50 °C. Explain which block will be storing the most energy.
2. Why does it take longer to boil a kettle full of water than one only half full?
3. Explain why stand- alone radiators are filled with oil, instead of being filled with air?
Questions
4. How much energy does it take to heat up 500g of lead by 30 °C ?
5. A washing machine heats 10kg of water for each wash cycle. How much energy is saved by washing clothes at 30 °C instead of 50 °C ?
6. A storage heater contains 100kg of concrete. 1800kJ of energy is transferred to it. What is the temperature change of the concrete?