Calculating Heat. Specific Heat Amount of heat energy needed to raise the temp of 1 ml of a substance 1°C For water the specific heat is 4.19 J/g °C,

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Presentation transcript:

Calculating Heat

Specific Heat Amount of heat energy needed to raise the temp of 1 ml of a substance 1°C For water the specific heat is 4.19 J/g °C, but it is differenct for different substances It takes 4.19 J to raise the temp of 1 g of water 1 °C Every substance has a different specific heat

Table of Specific Heats

Calculating Heat When Substance in One Phase Heat released or absorbed can be calculated by multiplying three factors Heat = specific heat x mass x temp change q = c x m x Δt

Practice The specific heat of water is 4.19 J/ g  C. How much heat is needed to warm 350g of water from 25  C to 75  C? If 178 J of heat is needed to increase the temperature of a 20g piece of copper metal from 25  C to 48  C, what is the specific heat of copper?

Heat and Phase Change (Evaporation) Heat of vaporization (  H vao ) energy required to change one gram of a substance from liquid to gas. For water 2260J/g Q =  H vao m

Practice The heat of vaporization of water is 2260J/g. How much heat must be supplied to evaporate 50g of water? How much heat is required to evaporate 150.g of a substance at its boiling point if it has a  H vap = 987 J/g?

Energy and Phase Change Heat of fusion (  H fus ) energy required to change one gram of a substance from solid to liquid. For water 340 J/g Q =  H fus m

Examples The heat of fusion of ice at 0°C is 340J/g. How much heat is needed to change 75g of ice at 0°C to a liquid at the same temperature? The heat of fusion of water at 0°C is 340J/g. How much heat is released when 250g of water changes to ice at 0°C?

Practice How much heat is needed to change 100g of water at 50  C to steam at 120  C? The specific heat of water is 4.19 J/g  C, the specific heat of steam is 1.7 J/g  C, and the heat of vaporization of water is 2260 J/g. How much heat must be released as 50g of water at 25  C to ice at -10  C? The specific heat of water is 4.19 J/g  C, the specific heat of ice is 2.1 J/g  C, and the heat of fusion fro water is 340 J/g.