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Make a model-melting ice on two blocks
Make diagram that shows what is happening Explain why this is happening in the diagram
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Calorimetry
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Calorimeter qrxn = - (qwater) Calorimetry video Reaction at Constant P
DH = qrxn Calorimetry video qrxn = - (qwater) No heat enters or leaves!
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Specific heat at constant pressure
Calculating heat Absorbed or released 𝑞=𝑚𝑠∆𝑇 Change in temperature 𝑇 𝑓 − 𝑇 𝑖 Unit: C Heat Unit: J or kJ Mass Unit: g Specific heat at constant pressure J/gC
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Specific Heat = c Specific heat of a substance is the amount of heat required to raise the temperature of one gram of that substance by one degree Celsius. Unit for specific heat is J/goC
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Heat capacity The amount of heat required to raise the system’s temperature by one Celsius.
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Each substance has a different specific heat
The lower the specific heat the lower the amount energy is required to raise its temperature.
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Example 1 If the temperature of 56.6g of ethanol increases from 45.0°C to 80.0°C, how much heat has been absorbed by the ethanol? Specific heat of ethanol =2.44J/g°C
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Example 2 A 4.00g sample of a substance was heated from 274K to 314K and absorbed 32J of heat, what is the specific heat of the substance?
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Example 3 If 98,000 J of energy are added to 6200 g of water at 14.0C, what will the final temperature of the water be? Specific heat of water = J/gC
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Example 4 A 45.0g sample of metal is placed in boiling water until its temp. is 100.0C. a calorimeter contains 100.0g of water at a temp of 24.4C. the metal sample is removed from the boiling water and immediately placed in water in the calorimeter. The final temp of the metal and water in the calorimeter is 34.9C. assuming that the calorimeter provides perfect insulation, what is the specific heat of the metal?
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Example 5 240g of water (initially at 21C) are mixed with an unknown mass of ion (initially at 501C). When thermal equilibrium is reached, the system has a temperature of 42 C. find the mass if the iron. Specific heat of iron = J/gC
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Example 6 240g of water (initially at 21C) are mixed with an unknown mass of ion (initially at 501C). When thermal equilibrium is reached, the system has a temperature of 42 C. find the mass if the iron. Specific heat of iron = J/gC
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Example 7 Determine the final temperature when a 25.0g piece of iron at 85.0C is placed into 75.0 grams of water at 20.0C.
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Review Video-Crash Course Chemistry #19
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