Heat A Form of Energy Molecules and Motion The motion of molecules produces heat The more motion,...
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Transcript of Heat A Form of Energy Molecules and Motion The motion of molecules produces heat The more motion,...
![Page 1: Heat A Form of Energy Molecules and Motion The motion of molecules produces heat The more motion, the more heat is generated.](https://reader035.fdocuments.in/reader035/viewer/2022070305/551593ad55034674578b5aa5/html5/thumbnails/1.jpg)
Heat
A Form of Energy
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Molecules and Motion
•The motion of molecules produces heat
•The more motion, the more heat is generated
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Heat Transfer
•The movement of heat from a warmer object to a colder one
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Forms of heat transfer
•Three forms of heat transfer:
•Conduction•Convection •Radiation
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Conduction
•Conduction involves the transfer of heat through direct contact
•Heat conductors conduct heat well, insulators do not
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Convection
•Takes place in liquids and gases as molecules move in currents
•Heat rises and cold settles to the bottom
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Radiation
• Heat is transferred through space
•Energy from the sun being transferred to the Earth
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Questions
• What are the three types of heat transfer?
• How is conduction different from radiation?
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What type of heat transfer is involved?
•Heating a room with a fireplace
•Egg cooking in a frying pan•Roof of a house becoming
hot
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What type of heat transfer?
•Warm air mass bringing a change in the weather
•Wire getting hot from an electric appliance
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Temperature and Heat
•Kinetic energy is the energy of motion
•Temperature is the measure of the average kinetic energy of an object
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Question
•How is kinetic energy related to heat production?
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Thermometer
• A instrument used to measure temperature
• Thermometers commonly have alcohol (with dye) or mercury
• Digital thermometers have replaced older ones
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Celsius Scale
•Celsius is the metric scale for measuring temperature
•Water freezes at 0ºC and boils at 100ºC
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Kelvin scale
•The Kelvin scale is a metric temperature scale measured in Kelvin units (K)
•Formula (273+ºC)= Kelvin
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Questions
• What is the formula for converting a Celsius temperature to a Kelvin temperature?
• What is the boiling point of water on the Kelvin scale?
• What is the freezing point of water on the Kelvin scale?
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Absolute zero
•The temperature in which all molecular motion stops (0 K)
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Questions
•Describe absolute zero.•What is absolute zero on the Celsius scale?
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Measuring Heat
•Increase in temperature •Addition of heat •A decrease in temperature •Removal of heat
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Calories
•Unit for measuring heat•The amount of heat needed to raise 1 gram of water one degree Celsius
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Temperature
•Joule is another unit for measuring heat
•Mass and type of substance determine the amount of temperature change
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Specific Heat
•The ability of a substance to absorb heat energy (specific heat)
•Different substances absorb heat at different rates
•The greater the mass of the object the more heat is absorbed
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What is a calorimeter?
•Device used to measure the heat given off during chemical reactions
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Questions
•How can heat be measured?
•What is the unit used to measure heat?
•What is specific heat?
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Heat and Phase Changes
•A phase change is a physical change that requires a change in heat energy
•Addition or removal of HEAT
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Questions
•What is freezing point, melting point, and boiling point?
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Heat expansion
•The expansion of a substance due to heat
•Most solids, liquids, and gases expand as they are heated
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Expansion of water
•Between 4ºC and 0ºC, water EXPANDS as it cools and turns into a solid
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Thermostat
•A thermostat is a device that controls the temperature
•The switch of a thermostat is a bimetallic strip
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Bimetallic Strip
•Two different metals that are bound together
•They expand at different rates when heated
•Used as a switch in a thermostat
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Internal energy
•The energy within a substance
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Questions
•What is internal energy?•What is a thermostat?•Describe the switch of a
thermostat.•What happens to most
substances when heat is added?