HEAT ENERGY

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Thermal Energy A. Temperature Heat 1.
Temperature is related to the average kinetic
energy of the particles in a substance.
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2. SI unit for temp. is the Kelvin a. K
C 273 (10C 283K) b. C K 273 (10K
-263C)
3. HEAT Energy the total of all the kinetic
and potential energy of all the particles in a
substance.
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• Types of energy
• POTENTIAL ENERGY
• STORED ENERGY. The energy inside the
  substance.
• KINETIC ENERGY Associated with motion.
• Average KE TEMPERATURE

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Energy

• The ability to do work.
• You measure energy in joules (J).
• Exothermic- energy given off in a chemical
  reaction.
• Endothermic- energy absorbed in a chemical
  reaction.

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FORMS OF ENERGY

• Chemical Energy- Energy released or absorbed in
  a chemical reaction. Ex. Oil burning (when oil
  burns, chemical energy is changed into heat
  energy.)
• Electrical Energy- Energy of the flow of
  electrons.
• Electromagnetic Radiation- Energy made up of
  waves, which include gamma rays, ultraviolet,
  light, radio waves, etc.
• Heat Energy- Random motion of atoms and
  molecules.
• Mechanical Energy- Energy in moving objects. Ex.
  Rock falling / car moving
• Nuclear Energy- Energy given off when a nucleus
  breaks up into smaller nuclei or when smaller
  nuclei unite to form a larger nucleus.

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PRINCIPLE OF CONSERVATION OF ENERGY

• Energy cannot be created nor destroyed.
• It can be transformed from one form to another or
  it can transferred from one body to another.

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HEAT ENERGY

• What is HEAT?
• Form of energy and measured in JOULES

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Heat and Temperature

• The temperature of an object tells us how HOT it
  is
• Measured in degrees Celsius - C
• It is NOT the same as heat energy although the
  two quantities are related. e.g. a beaker of
  water at 60 C is hotter than a bath of water at
  40 C BUT the bath contains more joules of heat
  energy

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Cup gets cooler while hand gets warmer
Heat a. The flow of thermal energy from
one object to another.
Heat always flows from warmer (HIGH T) to
cooler(LOW T) objects.
Ice gets warmer while hand gets cooler
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Heating and Cooling

• If an object has become hotter, it means that it
  has gained heat energy.
• If an object cools down, it means it has lost
  energy

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6. Specific Heat a. Some things heat up or
cool down faster than others.
Land heats up and cools down faster than water
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HEAT CAPACITY

• The amount of heat needed to increase the
  temperature of a material by 1oC. It depends on
  the MASS and the CHEMICAL COMPOSITION of the
  material.
•  
•  

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SPECIFIC HEAT CAPACITY

• The amount of heat needed to increase the
  temperature of 1 g of substance by 1 C.
• Depends only on the chemical composition.
•  

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HEAT OF FUSION FOR WATER (TABLE B)

• Amount of heat needed to completely melt 1g of
  water.
• 334 J/g
• 334 Joules of heat are necessary to completely
  melt 1 g of water.
• HOW MUCH HEAT IS NEEDED TO MELT 10 g OF WATER?

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HEAT OF VAPORIZATION FOR WATER (TABLE T)

• The amount of heat needed to completely vaporize
  one g of water at its boiling point.
• 2260 J/g
• Water needs 2260 J of heat per gram to convert to
  gas!

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How to calculate changes in HEAT The heat
absorbed or released in a chemical reaction
Q m x ?T x Cp Q HEAT m mass of
substance ?T change in temperature (Tf Ti) Cp
specific heat of substance
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Calorimeter
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Bomb Calorimetry

• A more sophisticated model is the bomb
  calorimeter, it has a chamber where a chemical
  reaction takes place and a device to start the
  reaction.