Temperature, Heat, and Expansion

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Temperature, Heat, and Expansion

• All matter is in constant motion, so the atoms
  and molecules of all matter have kinetic energy.
  This kinetic energy causes the effect of warmth.
  Whenever something becomes warmer, the kinetic
  energy of its atoms or molecules has increased.
• Created by N. Ferreira with the help of A. Kirby

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Temperature

• The quantity that tells us how hot or cold
  something is compared with a standard is
  temperature. It is defined as the measurement of
  the average kinetic energy of the motion of the
  molecule.

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Temperature

• Nearly all matter expands when its temperature
  increases and contracts when its temperature
  decreases. Thermometers measure the temperature
  by showing expansion or contraction of a liquid
  usually mercury or alcohol using a scale

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• The Celsius scale is the temperature scale with 0
  the melt-freeze temperature for water and 100 the
  boil-condense temperature of water at standard
  pressure. This is the most widely used scale.
• The Fahrenheit scale is the temperature scale in
  common use in the United States. The number 32 is
  assigned to the freezing point of water, and the
  number 212 to the boiling point of water.

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• The SI scale of temperature that is used in
  scientific research is the Kelvin scale. Its
  degrees are the same size as the Celsius degree
  and are called kelvins. The lowest possible
  temperature is 0 kelvin and is called absolute
  zero. At this temperature all motion ceases, so
  the substance has no kinetic energy.

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• Temperature is the measure of the average kinetic
  energy of the substance, not the total kinetic
  energy. In other words, there is more kinetic
  energy in a bucketful of warm water than in a
  cupful of water, but if the temperature of the
  two samples is the same, the average kinetic
  energy of the two is the same.

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Heat

• The energy transfer from one object to another
  because of a temperature difference between them
  is called heat. The direction of the energy
  transfer is always from a hot substance to a cold
  substance.
• The energy resulting from heat flow is called
  thermal energy which is also called internal
  energy.

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• When heat flows from one object or substance to
  another it is in contact with, the objects are
  said to be in thermal contact. Heat flows from
  the higher-temperature substance into the
  lower-temperature substance. Heat never flows on
  its own from a cold substance to a hot substance,
  just like water will never flow uphill by itself.

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Thermal Equilibrium

• Thermal Equilibrium is the state of two or more
  objects or substances in thermal contact when
  they have reached a common temperature.
• Describe why a thermometer works in identifying
  the temperature of a substance.
• Heat flows between the thermometer and the
  object until they have the same temperature.

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Internal Temperature

• The grand total of all energies inside a
  substance is called internal energy. A substance
  contains internal energy, not heat
• .

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Measurement of Heat

• How can the amount of heat transferred from one
  substance to another be determined?
• By measuring the temperature change of a known
  mass of water that absorbs heat.
• The resulting temperature of a substance depends
  on the mass and kind of substance affected.

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• The most common unit for heat is the calorie,
  which is defined as the amount of heat needed to
  raise the temperature of 1 gram of water by 1
  degree Celsius.
• Heat is also measured in Joules

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Specific Heat Capacity

• The amount of energy or quantity of heat required
  to raise the temperature of a unit of mass of a
  substance by one degree Celsius is called
  specific heat capacity (often called specific
  heat).
• Specific heat capacity is like thermal inertia
  since it signifies the resistance of a substance
  to changes in its temperature.

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Check Understanding

• Which has a higher specific heat capacity water
  or sand?
• Water does, thats why it takes longer for water
  to warm up and cool down.

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21.7 The Higher Specific Heat Capacity of Water

• Water has a much higher capacity for storing
  energy than most substances.
• Why is water a useful cooling agent?
• Because it can absorb a great deal of heat
  without changing temperature.