5 Water has a relatively large heat capacity It takes a lot of energy to raise the temperature of waterThis means that unlike other substances water can absorb lots of the sun’s energy and it will not change its temperature dramatically
6 Waters high heat capacity also means that it looses energy relatively slow So as the sun goes down and night falls the water will still remain a relatively constant temperature
8 If water had a low heat capacity Only a little bit of thermal energy would be needed to raise the temperatureSo all day long as the Sun’s energy was absorb by the water the temperature would raise dramatically
9 This would also mean that during the night water would loose it’s heat very fast and the temperature would drop quickly!!!
10 What can we take from this Water’s high heat capacity allows it to moderate temperature despite the huge fluctuations of thermal energy that it receives during the day and night.Without it waters temperature would change drastically throughout the course of a day
11 The Specific Heat Capacity How much energy it takes to raise the temperature for 1.0 g of a substance by 1° C is called the specific heat capacityWe can find out how much energy is needed to change an objects temperature with this equation:Q = mcΔT
12 Q is bigger Effects of Mass on Heat Large object = mcΔT Smaller object Q is smallerThink of boiling water for tea or cooking, more water means more time and energyHot water tanks at homeConclusion: bigger objects need more energy to raise their temperature
13 Q is bigger Effect of SHC on Heat Large Specific Heat = mcΔT Smaller Specific Heat= mcΔTQ is smaller4.18 J/g·°C0.32 J/g·°CConclusion: bigger SHC need more energy to raise their temperature by the same amount
14 Effect of Temp Change on Heat Large Temp Change= mcΔTQ is biggerSmaller Temp change= mcΔTQ is smallerConclusion: bigger SHC need more energy to raise their temperature by the same amount
15 Energy that doesn’t raise temperature Not all of the energy that is absorbed by water is used to raise it’s temperature.Some of the energy is used to evaporate the water and is not used to increase the temperature
16 The amount of energy it takes to convert 1 The amount of energy it takes to convert 1.0 g of water to a gaseous state is called the heat of vaporizationWe can find how much energy it will take to evaporate liquid water with this equationQ = mΔH°vapNotice there is no symbol for temperature because none of the energy required (Q) is being used to change the temperature during a state change
17 Energy that doesn’t raise temperature con’t The same can be said for changing solid water into liquid water (fusion, aka: melting)We call the energy required to convert 1.0 g of solid water to the liquid state the heat of fusion
18 We can find how much energy it will take to evaporate liquid water with this equation Q = mΔH°fusNotice there is no symbol for temperature because none of the energy required (Q) is being used to change the temperature during a state change
19 Compared to other substances Water’s heat of vaporization and heat of fusion are relatively larger than other substances.This means it will need to absorb lots of energy to melt or evaporate water – energy that will not be used to change water’s temperature
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