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16.1: Thermal Energy and Matter
Heat • Heat is the transfer of thermal
energy from one object to another because of a temperature difference.
• Heat flows spontaneously from hot objects to cold objects.
Temperature
• Temperature is a measure of how hot or cold an object is compared to a reference point.
•On the Kelvin scale, absolute zero is defined as a temperature of 0 kelvins.
Temperature • As an object heats up, its particles move
faster, on average. The average kinetic energy of the particles increases.
• One way that heat flows is by the transfer of energy in collisions.
• On average, high-energy particles lose energy. Low-energy particles gain energy.
Thermal Energy • Thermal energy is the total
potential and kinetic energy of all the particles in an object.
• Thermal energy depends on the mass, temperature, and phase (solid, liquid, or gas) of an object.
Specific Heat • The amount of heat needed to raise
the temperature of one gram of a material by one degree Celsius.
• The lower a material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass.
Calculating Specific Heat
• In this formula, heat is in joules, mass is in grams, specific heat is in J/g•°C, and the temperature change is in degrees Celsius.
Calculating Specific Heat
An iron skillet has a mass of 500.0 grams. The specific heat of iron is
0.449 J/g•°C. How much heat must be absorbed to raise the skillet’s
temperature by 95.0°C?
Calculating Specific Heat
• An iron skillet has a mass of 500.0 grams. The specific heat of iron is 0.449 J/g•°C. How much heat must be absorbed to raise the skillet’s temperature by 95.0°C?
Calculating Specific Heat
How much heat is needed
to raise the temperature of 100.0 g of water by
85.0°C?
Calculating Specific Heat
How much heat is needed to raise the temperature of 100.0 g of water by 85.0°C?
Q = m * c * ∆T = (100.0 g)(4.18 J/g•°C)(85.0°C)
= 35.5 kJ
Calculating Specific Heat
How much heat is
absorbed by a 750-g iron skillet when its
temperature rises from 25°C to 125°C?
Calculating Specific Heat
How much heat is absorbed by a 750-g iron skillet when its temperature
rises from 25°C to 125°C?
Q = m * c * ∆T = (750 g)(0.449 J/g•°C)(125°C – 25°C)
= (750 g)(0.449 J/g•°C)(100°C) = 34 kJ
Calculating Specific Heat
• In setting up an aquarium, the heater transfers 1200 kJ of heat to 75,000 g of water. What is the increase in the
water’s temperature? (Hint: Rearrange the specific heat formula
to solve for ∆T
Calculating Specific Heat
• In setting up an aquarium, the heater transfers 1200 kJ of heat to 75,000 g of water. What is the increase in the water’s temperature? (Hint: Rearrange the specific heat formula to solve for ∆T
∆T = Q / (m x c) = 1,200,000 J/(75,000 g × 4.18 J/g•°C)
= 3.8°C
Calculating Specific Heat
• To release a diamond from its setting, a jeweler heats a 10.0-g
silver ring by adding 23.5 J of heat. How much does the temperature of the silver
increase?
Calculating Specific Heat
• To release a diamond from its setting, a jeweler heats a 10.0-g silver ring by adding 23.5 J of heat. How much does the temperature of the silver increase?
∆T = Q / (m x c) = 23.5 J/(10.0 g × 0.235 J/g•°C)
= 10.0°C
Calculating Specific Heat
• What mass of water will
change its temperature by 3.0°C when 525 J of
heat is added to it?
Calculating Specific Heat
• What mass of water will change
its temperature by 3.0°C when 525 J of heat is added to it?
m = Q / (∆T x c) = 525 J/(3.0°C × 4.18 J/g•°C)
= 42 g
Calculating Specific Heat
How many joules of heat are
needed to raise the temperature of 10g of aluminum from 22 C to
55 C, if the specific heat of aluminum is 0.90J/g C?
Calculating Specific Heat
100g of 4 C water is heated until its temperature is 37 C. Calculate the amount of heat energy needed to cause this
rise in temperature.
Calculating Specific Heat
How much heat is needed to raise the temperature of 16g of iron from 25 C to
175 C?
Calorimeter
An instrument used to measure changes in
thermal energy.
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