Heat and Thermal Energy Temperature is a measure

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Heat and Thermal Energy

Heat and Thermal Energy

Temperature is a measure of the average kinetic energy of the molecules in an

Temperature is a measure of the average kinetic energy of the molecules in an object 2 Temperature scales: - °C → 0°C = freezing point of distilled water → 100°C = boiling point of distilled water at sea level - Kelvin K → 0 K = absolute 0 scale: 1°C = 1 K 0 K = -273°C 0°C = 273 K

Converting between °C and K Eg. convert 12°C → K Eg. convert 87 K

Converting between °C and K Eg. convert 12°C → K Eg. convert 87 K → °C

Heat Definition: the flow of thermal energy due to a change in temperature

Heat Definition: the flow of thermal energy due to a change in temperature

Heat Q = m. CΔT Q = thermal energy (J) m = mass (kg)

Heat Q = m. CΔT Q = thermal energy (J) m = mass (kg) C = specific heat (J/kg • K) ΔT = change in temperature (Tf – Ti) specific heat is a measure of how much heat energy/kg a material can hold water = 4180 J/kg K ; aluminum = 903 J/kg K ; lead = 130 J/kg K

Example 1 How much heat energy is required to bring 250 g of water

Example 1 How much heat energy is required to bring 250 g of water from 20°C to a boil? Cw = 4180 J/kg K

Example 2 What temperature would an equal mass of aluminum reach with that much

Example 2 What temperature would an equal mass of aluminum reach with that much heat? CA = 903 J/kg K

Example 3 A block of iron (CI = 450 J/kg K) is heated by

Example 3 A block of iron (CI = 450 J/kg K) is heated by 10000 J of heat energy and it's temperature increases by 40°C. What is its mass?

Example 4 A 350 g iron knife blade (Ci = 450 J/kg K) has

Example 4 A 350 g iron knife blade (Ci = 450 J/kg K) has a temperature of 1525°C. It is dropped in a pail containing 2 L (=2 kg) of 20°C water. What is the final temperature of the water and the knife blade? (Cw = 4180 J/kg K)