Specific Heat

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Specific Heat
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What are the building blocks?
Specific Heat
This concept does not involve building or
breaking down of molecules but might involve a
mixture of elements or compounds.
How water heats up or cools down is the standard
for all other materials.
There is usually an interest to how metals heat
up. However, all materials heat up differently.
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FORCE ENERGY
Energy measured in calories is used for this
concept. A calorie is defined asThe amount of
heat energy needed to raise the temperature of
one gram of water one degree Celsius. Or the
amount of heat energy lost when one gram of water
cools one degree Celsius. This calorie is
different than the one you hear about for food.
A food calorie is 1,000 times larger. It is
often written with a capital C
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A 1000 CALORIE HAMBURGER
IS ACTUALLY
1,000,000 CALORIES
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MATHEMATICS
Specific Heat involves a rate of heating based on
weight
For water, there is one calorie for every one
gram and for every degree Celsius. One calorie
for each gram and for each degree Celsius. One
calorie per gram per degree Celsius. 1 cal g oC
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Observation
Different materials heat up at different rates.
90OC
90OC
1 kg of Aluminum
1 kg of Gold
20OC
20OC
Gold heats up about 7 times faster than Aluminum
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Different materials store different amounts of
heat energy.
90OC
1 kg of Water
90OC
1 kg of Gold
20OC
20OC
Water takes about 30 times longer to heat than
gold, meaning it stores about 30 times more
calories.
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Mission Impossible
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SEA BREEZE
Explained by the difference of the specific heat
of water versus soil.
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LAND BREEZE
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Observation
Different materials heat up at different rates.
90OC
90OC
1 kg of Aluminum
1 kg of Gold
20OC
20OC
Gold heats up about 7 times faster than Aluminum
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Different materials store different amounts of
heat energy.
90OC
90OC
1 kg of Aluminum
1 kg of Gold
20OC
20OC
By the time aluminum heats up to 90OC it will
have stored 7 times more calories of heat than
the gold did.
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Different materials store different amounts of
heat energy.
90OC
1 kg of Water
90OC
1 kg of Aluminum
20OC
20OC
Water takes about 5 times longer to heat than
aluminum, meaning it stores about 5 times more
calories.
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1 calorie is defined as the amount of energy
needed to raise 1 gram of water 1 degree Celsius
90OC
1 kg of Water
1 kg of water would take 1,000 calories for each
degree. Our 700C increase would take 1,000 x 70
70,000 calories.
20OC
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1 mL or 1 cm3 (cc) of water has the mass of 1
gram.1,000 mL 1 Liter has mass of 1 kilogram
1 kg of water would take 1,000 calories for each
degree. Our 700C increase would take 1,000 x 70
70,000 calories.
90OC
1 kg of Water
1 Liter water
70,000 calories 70 kilocalories
70,000 calories 70 Calories
20OC
Food calories
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The specific heat of water is1 calorie per 1
gram per 1 degree Celsius 1 cal
g 0C
Specific Heat of Water

4.184 Joules 1 calorie
Joule The energy used by 1 watt for 1 second
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__ g
1 cal g 0C
__ 0C
X
X
Let the dimensions tell you how to solve problems.
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The specific heat of other materials can be
calculated by measuring the temperature rise of
water.
Blacksmiths may have been the first to recognize
this approach.
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Need modern blacksmith
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The specific heat of other materials can be
calculated by measuring the temperature rise of
water.

• Grams
• Water
• Metal
• Initial and Final Temperatures
• Water
• Metal

Since specific heat is calories per gram per
degree (raised/lowered) we need to keep track of
what quantities?
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Conservation of Energy
Energy Lost Energy Gained
Calories Lost Calories Gained
Joules Lost Joules Gained
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Winter Survivaland a Safe Source of Heat for
Field Operations
A request for investigation into the heat
capacity of available materials
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Problem with heating tents

• Heating the inside of tents is dangerous because
  of the potential for fire and carbon monoxide
  poisoning. It seems that heating objects outside
  the tent and then bringing them inside would be
  safer.

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• Candidates considered for heating are metal
  objects like aluminum or iron.
• Rocks found in the vicinity could also be used.
• Water is another candidate.

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Water Pros and Cons

• On a gram for gram basis, water stores heat much
  more efficiently than any other candidates.
  However, water can only be brought to 100 degrees
  Celsius before it boils, and then it wont get
  any hotter unless placed under pressure, which is
  dangerous.
• Water is also a precious commodity in some
  regions, so risking a spill may not be worth it.

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Metal Pros and Cons

• Some of the metal tools and equipment might be
  used. However, in a quick evacuation of camp it
  might cause problems if these items are too hot
  to handle.

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Rocks Pros and Cons
Rocks seem like the best candidate. However, we
have no data on how efficient rocks can store
heat, especially of rocks containing a mixture of
minerals.
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There are stories of soldiers and others who said
they heated up rocks, brought them into their
tent, and the rocks warmed up the tent. This is
good to know, but there is much information
missing.
Needed questions Where between extremes
What was the mass of the heated rocks? Was it a few one-pound rocks or half a ton of rocks?
How hot were the rocks? Were they heated to body temperature or to several hundred degrees in a fire?
How cold was the tent? Was it only a cool 50 degrees Fahrenheit or a bone-chilling 20 degrees below zero?
How big was the tent? Was it a standard one person tent or a large command post tent?
How much did it warm the tent? Did it raise a few degrees or 50 or more degrees?
To calculate heat energy released from rocks we
could calculate the heat energy gained by the
tent, which is difficult because of the different
materials in the tent. However, we could use
waterinstead because we knowthat it takes one
calorieto raise one gram of water one degree
Celsius.
Heat energy released by rocks Heat energy
gained by water
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In practice, it wouldnt be that easy to find a
rock equal to one gram or to drop it into one
gram of water. Therefore, the calculations will
need to adjust for the mass of the rock and the
mass of the water.
A rock could be heated by a flame but it would be
difficult to measure the rocks temperature.
Another way would be to place the rock in boiling
water and then measure the temperature of the
water. Then the heated rock could be placed in
a known amount of water and the temperature rise
of the water could be recorded.




















Should be near 100oC




















Other heat sources could be used (hotplate, stove
top, etc.)
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Name _________________
Its February and you want to heat up your pool.
It is currently 50oF (10oC) and you want it
raised to 80oF (27oC) Using an electric heater,
how much will it cost if 1 kilowatt-hour is 10
cents? The pool is 7.0 meters long, 5.0 meters
wide and 2.0 meters deep. A. Whats the volume
in cubic meters? ______ B. What is the volume
in cubic centimeters?___________ C. What is the
total grams of the water? ____________
1 cc of water weighs 1 gram
A calorie is defined as the energy needed
to raise one gram of water one degree Celsius.
D. How many calories will it take to raise the
pool water from 10oC to 27oC? _______________ E
. 1 calorie 1.1 x 10-6 kilowatts hours. How
many kilowatt-hours will you need?
____________ F. How much will it cost to heat
the pool from 50oF (10oC) to 80oF (27oC)?
_______________
grams 17oC 1 calorie

g. oC
calories 1.1x10-6
kilowatt-hrs
_______ kilowatt-hours 0.10    
calories
kilowatt-hr
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Calories Lost Calories Gained
calories lost by metal calories gained by water
grams x 1 cal x (Tf - Ti) g 0C
grams x SH x (Tf - Ti)
SH x g 0C amount calories gained by water
g 0C amount g 0C amount
Specific Heatmetal calories gained by metal
g 0C