Living By Chemistry SECOND EDITION Unit 5 FIRE
Living By Chemistry SECOND EDITION Unit 5: FIRE Energy, Thermodynamics, and Oxidation-Reduction
Lesson 97: Heat Versus Temperature Heat Transfer
Chem. Catalyst Which will melt more of a snowman, a cup of water at 90 °C or a large barrel of water at 20 °C? Explain your thinking.
Key Question What is the difference between temperature and heat?
You will be able to: • • • define a calorie complete simple calculations involving heat transfer for water samples describe basic differences between thermal energy, heat, and temperature
Prepare for the Lab Work in pairs.
Discussion Notes The final temperature of a mixture depends on both the mass and the temperature of the samples. Heat and temperature are different concepts. Thermal energy refers to the amount of energy in a sample. Thermal energy: The total kinetic energy associated with the mass and motions of the particles in a sample of matter.
Discussion Notes (cont. ) The calorie is a unit of energy used to measure heat transfer and to express thermal energy. q = m(1 cal/g °C)∆T heat transferred = (mass)(1 cal/g °C)(change in temperature) The value 1 cal/g °C applies only to water. Calorie: The amount of energy it takes to raise the temperature of one gram of water by one Celsius degree.
Wrap Up What is the difference between temperature and heat? • Temperature is a measure of the average kinetic energy of the atoms and molecules in a sample. • The thermal energy is a measure of the total kinetic energy of all the atoms and molecules in a sample and is dependent on both the mass of the sample and its temperature. • Thermal energy can only be measured as heat transfer between two samples of known temperature and mass.
Wrap Up (cont. ) • Heat transfer, q, is measured in calories. The amount of energy required to raise 1 g of water by 1 ° C is 1 calorie. For water, q = m(1 cal/g °C)∆T.
Check-In You have one beaker containing 500 g of water at 75 °C. You also have a beaker with 2000 g of water at the same temperature. Which will melt more ice? Explain your answer in terms of thermal energy, heat transfer, and temperature.
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