Heat And Temperature
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February 26, 2008 Science and Technology IV (Physics)
Heat and Temperature Jayson G. Chavez High School Department Malate Catholic School Malate, Manila
•
Galileo Galilei (1602) invented the first thermal meter.
•
Anders Celsius (1701-1744) a Swiedish astronomer who suggested the Celsius scale.
•
Gabriel Daniel Fahrenheit (1686-1736) the German physicist who popularized the use of the Fahrenheit scale. However this standard of temperature will become obsolete if the U.S. of A. will go metric.
•
William Thomson— The first Baron Kelvin (18241907), suggested a scale which is favored by scientists: The Kelvin Scale.
•
The energy transferred from one object to another because of a temperature difference between them is termed heat.
•
Matter does not contain heat, yet it contains molecular kinetic energy and “possibly” potential energy.
•
Heat is energy in transit from a body of higher temperature to one that has lower temperature.
“A body does not contain work, it does work or has work done on it.”
•
It is the quantity that indicates how hot or cold an object is based on a particular standard.
•
It measures the amount heat.
•
The length Lo of an object changes by an amount ΔL when its temperature changes by an amount ΔT. ΔL= αL0ΔT
Where: ΔL= change in length α = coefficient of linear expansion L0 = initial length ΔT= change in temperature “The common unit for the coefficient of linear expansion is 1/oC”
• A steel aircraft carrier is 450 m long when moving through the icy North Atlantic at a temperature of 1.5 o C. By how much does the carrier lengthen when it is travelling the Philippine Sea at a temperature of 27 oC? The coefficient of linear expansion of steel is 12 x 10-6
ΔL = αL0ΔT = (12 x 10-6 /oC) (450 m)(27 oC- 1.5 oC) = (12 x 10-6 /oC) (450 m)(25.5 oC) = (12 x 10-6 /oC) (11475m · oC) =
•
The volume Vo of an object changes by an amount ΔV when its temperature changes by an amount ΔT. ΔV=βV0ΔT
Where: ΔV= change in volume β = coefficient of volume expansion Vo = initial volume ΔT= change in temperature “The common unit for the coefficient of volume expansion is 1/oC”
A swimming pool contains 213 m3 of water. The sun heats the water from 17 oC to 27 oC. What is the change in the volume of water? The coefficient of volume expansion of water is 207 x 106
ΔV =βV0ΔT = (207 x 10-6 /oC) (213 m3 )(27 oC- 17 oC) = (207 x 10-6 /oC) (213 m3 )(10 oC) = (207 x 10-6 /oC) (2130m3 · oC) =
•
Conduction is the transfer of heat energy by molecular and electron collisions within a substance (especially solids).
•
Convection refers to the transfer of heat energy in a gas or liquid by means of currents in the heated fluid. “The fluid moves, carrying energy with it.”
•
Radiation is the transfer of energy by means of electromagnetic waves.
•
Heat transfer by conduction through the vacuum is impossible. Some heat escapes by conduction through the glass and the stopper, but this is a slow process, since glass, plastics, and corks are ought to be poor conductors.
•
The vacuum gas no fluid to convect, so there is no heat loss through the walls by convection.
•
Heat loss by radiation is reduced by the silvered surfaces of the walls which reflect heat waves back in the bottle.
•
The heat Q that must be supplied or removed to change the temperature of a substance of mass m by an amount of ΔT is: Q = mcΔT
Where: Q= heat m= mass of the object c= specific heat capacity ΔT= change in temperature “The common unit for the specific heat capacity of a substance is J/(kg· oC)”
“Simply specific heat capacity is the quantity of heat required to change the temperature of a unit mass of a substance by 1 oC.”
•
Cold water at a temperature of 15 0C enters a heater, and the resulting hot water, has a temperature of 61 o C. A person uses 120 kg of hot water in taking a shower Find the number of joules needed to heat the water.
The specific heat capacity of water at 15 oC is 4186 J/(kg· o C).
Q = mcΔT = (120 kg) [4186 J/(kg· oC)] (61oC – 15oC) = 2.3 x 107 Joules
•
In a half hour, a 65-kg jogger can generate 8.0 x 105 J of heat. This heat is removed from the jogger’s body by a variety of means, including the body’s own temperature regulating mechanisms. If the heat were not removed, how much would the body temperature increase?
The specific heat capacity of the human body at 37 oC is 3500 J/(kg· oC)
Q = mcΔT ΔT= Q/mc = 8.0 x 105 J/ (65 kg [3500 J/(kg· oC)]) = 3.5 oC
•
A technique used in determining the specific heat capacity of a substance.
•
The calorimeter cup is made from 0.15 kg aluminum and contains 0.20 kg of water. Initially, the water and the cup have a common temperature of 18.0 oC. An unknown material (m= 0.040 kg) is heated to a temperature of 97 oC and then added to the water. The temperature of the water, the cup, and the unknown material is 22.0 oC after thermal equilibrium is reestablished. Ignoring the small amount of heat gained by the thermometer, find the specific heat capacity of the unknown material.
The specific heat capacity of water and aluminum are 4186 J/(kg· oC) and 9.00 x 102 J/(kg· oC) respectively.
•
The latent heat L is the heat per kilogram that must be added or removed when a substance changes from one phase to another at constant temperature.
The SI Unit of Latent Heat is J/kg.
•
Evaporation is the change of phase from liquid to gas, this occurs at the surface of the liquid.
•
Condensation the opposite changing of gas to a liquid.
•
Boiling is the change of phase throughout the liquid.
•
Melting and Freezing
•
Sublimation
of
evaporation,
the
•
L is the heat per kilogram that must be added or removed when a substance changes from one phase to another at a constant temperature.
The SI Unit for Latent Heat is J/kg
•
Latent Heat of Fusion (Lf ) is the change between solid and liquid phases.
•
Latent Heat of Vaporization (Lv ) applies to the change between liquid and gas phases.
•
Latent Heat of Sublimation (Ls ) refers to the change between solid and gas phases.
•
The amount of energy required to change a unit mass of a substance from solid to liquid ( vice versa).
•
The amount of energy needed to change a unit mass of a substance from liquid to gas (and vice versa).
•
Ice at 0 oC is placed in a Styrofoam cup containing 0.32 kg of lemonade at 27 oC. Let us say that the specific heat capacity of lemonade is the same as water. After the ice and lemonade reach an equilibrium temperature, some ice still remains. Ignore the specific heat capacity of the cup and any heat lost to the surroundings. Determine the mass of ice that has melted.
The specific heat of water is 4186 J/(kg· oC) Latent Heat of Fusion of Ice is 33.5J/kg
•
A 7 kg glass bowl [c= 840 J /(kg· oC)] contains 16 kg of punch at 25.0 oC. Two and a half kilograms of ice [c= 2 x 103 J /(kg· oC)] are added to the punch. The ice has an initial temperature of -20.0 oC, having been kept in a very cold freezer. The punch may be treated as if it were water [c= 4186 J /(kg· oC)], and it may be assumed that there is no heat flow between the punch bowl and the external environment. What is the temperature of the punch, ice, and bowl when they reach thermal equilibrium.
Study Hard, Dream Big, and Reach Your Goals!!! Thank you and God Bless J.G.Chavez
Heat and Temperature Jayson G. Chavez High School Department Malate Catholic School Malate, Manila
•
Galileo Galilei (1602) invented the first thermal meter.
•
Anders Celsius (1701-1744) a Swiedish astronomer who suggested the Celsius scale.
•
Gabriel Daniel Fahrenheit (1686-1736) the German physicist who popularized the use of the Fahrenheit scale. However this standard of temperature will become obsolete if the U.S. of A. will go metric.
•
William Thomson— The first Baron Kelvin (18241907), suggested a scale which is favored by scientists: The Kelvin Scale.
•
The energy transferred from one object to another because of a temperature difference between them is termed heat.
•
Matter does not contain heat, yet it contains molecular kinetic energy and “possibly” potential energy.
•
Heat is energy in transit from a body of higher temperature to one that has lower temperature.
“A body does not contain work, it does work or has work done on it.”
•
It is the quantity that indicates how hot or cold an object is based on a particular standard.
•
It measures the amount heat.
•
The length Lo of an object changes by an amount ΔL when its temperature changes by an amount ΔT. ΔL= αL0ΔT
Where: ΔL= change in length α = coefficient of linear expansion L0 = initial length ΔT= change in temperature “The common unit for the coefficient of linear expansion is 1/oC”
• A steel aircraft carrier is 450 m long when moving through the icy North Atlantic at a temperature of 1.5 o C. By how much does the carrier lengthen when it is travelling the Philippine Sea at a temperature of 27 oC? The coefficient of linear expansion of steel is 12 x 10-6
ΔL = αL0ΔT = (12 x 10-6 /oC) (450 m)(27 oC- 1.5 oC) = (12 x 10-6 /oC) (450 m)(25.5 oC) = (12 x 10-6 /oC) (11475m · oC) =
•
The volume Vo of an object changes by an amount ΔV when its temperature changes by an amount ΔT. ΔV=βV0ΔT
Where: ΔV= change in volume β = coefficient of volume expansion Vo = initial volume ΔT= change in temperature “The common unit for the coefficient of volume expansion is 1/oC”
A swimming pool contains 213 m3 of water. The sun heats the water from 17 oC to 27 oC. What is the change in the volume of water? The coefficient of volume expansion of water is 207 x 106
ΔV =βV0ΔT = (207 x 10-6 /oC) (213 m3 )(27 oC- 17 oC) = (207 x 10-6 /oC) (213 m3 )(10 oC) = (207 x 10-6 /oC) (2130m3 · oC) =
•
Conduction is the transfer of heat energy by molecular and electron collisions within a substance (especially solids).
•
Convection refers to the transfer of heat energy in a gas or liquid by means of currents in the heated fluid. “The fluid moves, carrying energy with it.”
•
Radiation is the transfer of energy by means of electromagnetic waves.
•
Heat transfer by conduction through the vacuum is impossible. Some heat escapes by conduction through the glass and the stopper, but this is a slow process, since glass, plastics, and corks are ought to be poor conductors.
•
The vacuum gas no fluid to convect, so there is no heat loss through the walls by convection.
•
Heat loss by radiation is reduced by the silvered surfaces of the walls which reflect heat waves back in the bottle.
•
The heat Q that must be supplied or removed to change the temperature of a substance of mass m by an amount of ΔT is: Q = mcΔT
Where: Q= heat m= mass of the object c= specific heat capacity ΔT= change in temperature “The common unit for the specific heat capacity of a substance is J/(kg· oC)”
“Simply specific heat capacity is the quantity of heat required to change the temperature of a unit mass of a substance by 1 oC.”
•
Cold water at a temperature of 15 0C enters a heater, and the resulting hot water, has a temperature of 61 o C. A person uses 120 kg of hot water in taking a shower Find the number of joules needed to heat the water.
The specific heat capacity of water at 15 oC is 4186 J/(kg· o C).
Q = mcΔT = (120 kg) [4186 J/(kg· oC)] (61oC – 15oC) = 2.3 x 107 Joules
•
In a half hour, a 65-kg jogger can generate 8.0 x 105 J of heat. This heat is removed from the jogger’s body by a variety of means, including the body’s own temperature regulating mechanisms. If the heat were not removed, how much would the body temperature increase?
The specific heat capacity of the human body at 37 oC is 3500 J/(kg· oC)
Q = mcΔT ΔT= Q/mc = 8.0 x 105 J/ (65 kg [3500 J/(kg· oC)]) = 3.5 oC
•
A technique used in determining the specific heat capacity of a substance.
•
The calorimeter cup is made from 0.15 kg aluminum and contains 0.20 kg of water. Initially, the water and the cup have a common temperature of 18.0 oC. An unknown material (m= 0.040 kg) is heated to a temperature of 97 oC and then added to the water. The temperature of the water, the cup, and the unknown material is 22.0 oC after thermal equilibrium is reestablished. Ignoring the small amount of heat gained by the thermometer, find the specific heat capacity of the unknown material.
The specific heat capacity of water and aluminum are 4186 J/(kg· oC) and 9.00 x 102 J/(kg· oC) respectively.
•
The latent heat L is the heat per kilogram that must be added or removed when a substance changes from one phase to another at constant temperature.
The SI Unit of Latent Heat is J/kg.
•
Evaporation is the change of phase from liquid to gas, this occurs at the surface of the liquid.
•
Condensation the opposite changing of gas to a liquid.
•
Boiling is the change of phase throughout the liquid.
•
Melting and Freezing
•
Sublimation
of
evaporation,
the
•
L is the heat per kilogram that must be added or removed when a substance changes from one phase to another at a constant temperature.
The SI Unit for Latent Heat is J/kg
•
Latent Heat of Fusion (Lf ) is the change between solid and liquid phases.
•
Latent Heat of Vaporization (Lv ) applies to the change between liquid and gas phases.
•
Latent Heat of Sublimation (Ls ) refers to the change between solid and gas phases.
•
The amount of energy required to change a unit mass of a substance from solid to liquid ( vice versa).
•
The amount of energy needed to change a unit mass of a substance from liquid to gas (and vice versa).
•
Ice at 0 oC is placed in a Styrofoam cup containing 0.32 kg of lemonade at 27 oC. Let us say that the specific heat capacity of lemonade is the same as water. After the ice and lemonade reach an equilibrium temperature, some ice still remains. Ignore the specific heat capacity of the cup and any heat lost to the surroundings. Determine the mass of ice that has melted.
The specific heat of water is 4186 J/(kg· oC) Latent Heat of Fusion of Ice is 33.5J/kg
•
A 7 kg glass bowl [c= 840 J /(kg· oC)] contains 16 kg of punch at 25.0 oC. Two and a half kilograms of ice [c= 2 x 103 J /(kg· oC)] are added to the punch. The ice has an initial temperature of -20.0 oC, having been kept in a very cold freezer. The punch may be treated as if it were water [c= 4186 J /(kg· oC)], and it may be assumed that there is no heat flow between the punch bowl and the external environment. What is the temperature of the punch, ice, and bowl when they reach thermal equilibrium.
Study Hard, Dream Big, and Reach Your Goals!!! Thank you and God Bless J.G.Chavez
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