HEAT AND CALORIMETRY
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HEAT AND
CALORIMETRY
HEAT
•
Represented by
q
•
Energy that transfers from one object to
another because of a temperature difference
between them
•
Heat always flows from a warmer object to a
cooler object
UNITS TO MEASURE HEAT FLOW
•
2 ways – the calorie and the joule
•
calorie (cal) – the quantity of heat needed to raise the
temperature of 1 g of pure water 1
o
C
–
Always written with a small c (except with dietary calories)
•
Dietary Calorie is always written with a capital C
•
1 Dietary calorie is equal to one kilocalorie, or 1000 calories
1 Calorie = 1 kilocalorie = 1000 calories
JOULE
•
SI Unit of Energy (J)
•
One joule of heat raises the temp of 1 g of
pure water 0.2390
o
C
CONVERTING BETWEEN CALORIES
AND JOULES
1 J = 0.2390 cal
4.184 J = 1 cal
SPECIFIC HEAT
•
Represented by C
•
Amount of heat required to raise the
temperature of 1 g of the substance 1
o
C
–
This is why some things heat up more quickly
than others
EXAMPLE
•
C
water
= 4184 J/kg C
•
C
sand
= 664 J/kgC
•
This is why land heats up quickly during the day
and cools quickly at night and why water takes
longer
WHY DOES WATER HAVE SUCH A
HIGH SPECIFIC HEAT?
•
Water molecules form strong bonds with each
other; therefore it takes more heat energy to
break them
•
Metals have weak bonds and do not need as much
energy to break them
HOW TO CALCULATE CHANGES IN
THERMAL ENERGY
Q = mC
Q
= change in thermal energy
m
= mass of substance
= change in temperature (T
f
– T
i
)
C
p
= specific heat of substance
CALORIMETER
•
This is used to
help measure the
amount of heat
involved in a
chemical reaction
Covering the fundamentals of heat transfer, specific heat, and calorimetry, this informative content explains the units to measure heat flow, the concept of specific heat, and how to calculate changes in thermal energy. Discover why water has a high specific heat capacity and learn about the tools used, like calorimeters, in heat measurement experiments. Gain insights into converting between calories and joules, and explore examples showcasing different specific heat values for various materials. Delve into the world of heat and energy transformations with this comprehensive guide.
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Presentation Transcript
HEAT AND CALORIMETRY
HEAT Represented by q Energy that transfers from one object to another because of a temperature difference between them Heat always flows from a warmer object to a cooler object
UNITS TO MEASURE HEAT FLOW 2 ways the calorie and the joule calorie (cal) the quantity of heat needed to raise the temperature of 1 g of pure water 1oC Always written with a small c (except with dietary calories) Dietary Calorie is always written with a capital C 1 Dietary calorie is equal to one kilocalorie, or 1000 calories 1 Calorie = 1 kilocalorie = 1000 calories
JOULE SI Unit of Energy (J) One joule of heat raises the temp of 1 g of pure water 0.2390oC
CONVERTING BETWEEN CALORIES AND JOULES 1 J = 0.2390 cal 4.184 J = 1 cal
SPECIFIC HEAT Represented by C Amount of heat required to raise the temperature of 1 g of the substance 1oC This is why some things heat up more quickly than others
EXAMPLE Cwater= 4184 J/kg C Csand= 664 J/kgC This is why land heats up quickly during the day and cools quickly at night and why water takes longer
WHY DOES WATER HAVE SUCH A HIGH SPECIFIC HEAT? Water molecules form strong bonds with each other; therefore it takes more heat energy to break them Metals have weak bonds and do not need as much energy to break them
HOW TO CALCULATE CHANGES IN THERMAL ENERGY Q = mC T Q = change in thermal energy m = mass of substance T = change in temperature (Tf Ti) Cp = specific heat of substance
CALORIMETER This is used to help measure the amount of heat involved in a chemical reaction
