Heat Transfer and Thermodynamics
7 multiple choice
no constructed response
A couple of websites to help you out:
http://www.ftexploring.com/energy/energy-1.htm
http://genesismission.jpl.nasa.gov/educate/scimodule/heat/index.html
no constructed response
A couple of websites to help you out:
http://www.ftexploring.com/energy/energy-1.htm
http://genesismission.jpl.nasa.gov/educate/scimodule/heat/index.html
a. Know the principle of conservation of energy and apply it to energy transfers
http://www.grc.nasa.gov/WWW/K-12/airplane/thermo1.html
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEner1.html
Law of Conservation of Energy (also known as First Law of Thermodynamics)- in the middle of the 19th century, it was proposed by the English and German scientists that the total energy in the universe is constant. Essentially, energy cannot be created nor destroyed. Energy can, however, by converted from one form to another. The total amount of energy stays the same.
There are five different forms of energy present in the universe: mechanical (associated with the motion), heat, chemical, electromagnetic, and nuclear.
Examples of Energy Transfer:
A car engine burns fuel. This converts the fuel's chemical energy into mechanical energy in order to make the car move.
Windmills changes wind's energy into mechanical energy to turn turbines, which then produce electricity.
Solar cells changes the sunlight, which is radiant energy, into electrical energy.
Potential Energy- this type of energy has not yet been used.
Kinetic Energy- an object is considered to have kinetic energy if it has mass and is in use or in motion. The formula for kinetic energy is:
KE= 1/2mv2
Example:
A tank of gasoline has potential energy that is converted to kinetic energy by the engine.
b. Discuss how the transfer of energy as heat is related to changes in temperature
http://www.learner.org/courses/essential/physicalsci/session7/
Simply put, heat will naturally move from high to low temperatures. The region you find the higher temperature in is called the heat source. The region with lower temperature is called the heat sink. Heat and temperature are both measures of energy.
Heat does not equal temperature.
Heat- measures total kinetic energy of molecules in motion
Temperature- measures the average kinetic energy of the movement of particles. Higher temperature= faster particles. Lower temperature = slower particles.
Heat is always transferred in three ways:
Specific heat is the amount of heat needed to raise one gram of material one degree Celsius.
1 Calorie of heat will raise 1 gram of water 1 degree C.
Land areas warm up more rapidly than water areas for the same heat input.
Latent heat is the heat required to change a state of matter (from solid to liquid, or liquid to gas)
The water latent heat of fusion is 80 cal/g. The water latent heat of evaporation is 600 cal/g. When water evaporates, it takes heat from the environment. When it condenses, it releases heat to the environment. Latent heat of evaporation/condensation is an important sink/source of atmospheric energy. This latent heat drives hurricanes and thunderstorms.
Differences in ground temperatures causes hot and cool spots. Warm air is forced upwards by the cooler air (convection). Rising air parcel goes to lower pressure. Air parcel expands and cools (gas law). If the air parcel is still warmer (buoyant) than the environment, then it will continue to rise. On the other hand, if the air parcel is the same or cooler temperature than the environment, then it will stop rising.
d. Describe the methods of heat transfer by conduction, convection, and radiation, and provide examples for each
Conduction- transfer of energy through matter from one atom/molecules to the next within a substance. Conduction is most effective in solids, but can also take place in fluids. For clarification: the atoms/molecules do not move from one place to another. The energy is transferred by the electrons that are able to move about. An example of conduction is putting a lit match up to a metal needle. The heat is transferred along the needle as the heated electrons gain kinetic energy. The electrons begin to move fast in all directions, colliding with other atoms, passing on heat energy. The atoms, themselves, only vibrate and collide with their neighbors.
Aluminum, bronze, copper, gold, iron are just a few examples of materials that are good conductors.
More Examples:
Ice cube- an ice cube in your hand will eventually melt. The heat is being conducted from your hand into the ice cube.
Ironing- when ironing an item of clothing, the heat from the iron is transferred onto the clothing item.
Convection- heat is transferred in liquids and gases. It is due to the actual motion of the atoms/molecules by movement of currents. If liquid is heated, it expands, becomes less dense, and rises. The cooler, less dense fluid then sinks to take its place. An example of this transfer of heat is by the ocean. During the day, the land heats up faster than the sea. The cooler air over the sea sinks and takes the place of the air over the land, which is warmer (less dense) and rises up in the air. As this air cools over the ocean, it sinks and the cycle continues.
More Examples:
Mantle-The rocky mantle of the earth is slowly moving due to the convection currents that transfers heat from the interior of the Earth towards the surface. This is the reason why the tectonic places are slowly moving around the Earth.
Hot air balloon- The heater inside the balloon heats the air. This warm air moves upward causing the balloon to rise as a result of the hot air trapped inside. In order to descend, you release some of this hot air, allowing cool air to replace it.
Radiation- heat energy in the form of electromagnetic waves is transferred from a hotter to a cooler place without the use of a medium. An example would be the sun. Since there is no large object connecting the Earth and the sun, then conduction cannot take place to bring energy to Earth. In addition, since there is no fluid or gas in space, then convection cannot take place. Thus, the only method in which energy can reach the earth is through electromagnetic waves from the sun.
More Examples:
Microwaves
Radio waves
Campfire's heat- the energy of heat can make light. This light, being a wave, carries energy and moves from one place to another in straight lines. This is the reason that when you are facing the fire, only the front is warmed.
e. Explain how chemical energy in fuel is transformed to heat
Chemical energy is stored in fuel as potential energy and can be released when these compounds undergo chemical reactions. For example, when fuel is burned, the chemical energy is converted to heat energy (exothermic).
The chemical energy in food is converted by the body into mechanical energy and heat.
f. Design and explain experiments to induce a physical change such as freezing, melting, or boiling
http://mypages.iit.edu/~smile/guests/chgstate.htm
http://www.teach-nology.com/teachers/lesson_plans/science/chemistry/reactions/
g. Distinguish between physical and chemical changes and provide examples of each
http://www.learner.org/courses/essential/physicalsci/session4/
http://www.learner.org/courses/essential/physicalsci/session3/
http://www.sciencenetlinks.com/lessons.php?BenchmarkID=4&DocID=402
Physical Change- in a physician change, the chemical composition of the object does not change. If you melt ice, the physical change has occurred (solid substance into a liquid substance, but its chemical composition is still the same (water), H2O).
Chemical Change- in a chemical change, a chemical reaction takes place. The composition of the object changes and we observe a new set of properties; the formation of a new substance. For example, an antacid dropped in a glass of water produces water. A firework displays colorful lights. When a new substance is formed, we usually observe one or more of the following:
1. Frying an egg
2. vaporization of dried ice
3. boiling water
4. burning gasoline
5. baking Cookies
6. souring milk
Answer:
1. Frying an egg ==> Chemical Change
2. vaporization of dried ice ==> Physical Change
3. boiling water ==> Physical Change
4. burning gasoline ==> Chemical Change
5. baking Cookies ==> Chemical Change
6. souring milk => Chemical Change 6. Chemical Change
© Science CSET: Free Prep Guides, 2008. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Science CSET: Free Prep Guides with appropriate and specific direction to the original content.
http://www.grc.nasa.gov/WWW/K-12/airplane/thermo1.html
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEner1.html
Law of Conservation of Energy (also known as First Law of Thermodynamics)- in the middle of the 19th century, it was proposed by the English and German scientists that the total energy in the universe is constant. Essentially, energy cannot be created nor destroyed. Energy can, however, by converted from one form to another. The total amount of energy stays the same.
There are five different forms of energy present in the universe: mechanical (associated with the motion), heat, chemical, electromagnetic, and nuclear.
Examples of Energy Transfer:
A car engine burns fuel. This converts the fuel's chemical energy into mechanical energy in order to make the car move.
Windmills changes wind's energy into mechanical energy to turn turbines, which then produce electricity.
Solar cells changes the sunlight, which is radiant energy, into electrical energy.
Potential Energy- this type of energy has not yet been used.
Kinetic Energy- an object is considered to have kinetic energy if it has mass and is in use or in motion. The formula for kinetic energy is:
KE= 1/2mv2
Example:
A tank of gasoline has potential energy that is converted to kinetic energy by the engine.
b. Discuss how the transfer of energy as heat is related to changes in temperature
http://www.learner.org/courses/essential/physicalsci/session7/
Simply put, heat will naturally move from high to low temperatures. The region you find the higher temperature in is called the heat source. The region with lower temperature is called the heat sink. Heat and temperature are both measures of energy.
Heat does not equal temperature.
Heat- measures total kinetic energy of molecules in motion
Temperature- measures the average kinetic energy of the movement of particles. Higher temperature= faster particles. Lower temperature = slower particles.
Heat is always transferred in three ways:
- Convection- movement of huge amounts of material taking the heat from one area and bringing it in another. For example, when warm air (less dense) rises, cold air which is more dense sinks to replace it. The heat has moved.
- Radiation- transfer of energy where there is no conductive medium (for example in space) for heat to transfer through. Heat takes place instead in the form of electromagnetic waves. When these waves fall on an object, some of the energy is absorbed, increasing the objects internal energy.
- Conduction- heat source and heat sink are connected by matter. Transfer of heat occurs through collisions. Heat energy is transferred in solids, liquids, and gases (but in a lesser extent). Energy is transported by conduction as molecules vibrate, rotate, and/or collide into each other.
Specific heat is the amount of heat needed to raise one gram of material one degree Celsius.
1 Calorie of heat will raise 1 gram of water 1 degree C.
Land areas warm up more rapidly than water areas for the same heat input.
Latent heat is the heat required to change a state of matter (from solid to liquid, or liquid to gas)
The water latent heat of fusion is 80 cal/g. The water latent heat of evaporation is 600 cal/g. When water evaporates, it takes heat from the environment. When it condenses, it releases heat to the environment. Latent heat of evaporation/condensation is an important sink/source of atmospheric energy. This latent heat drives hurricanes and thunderstorms.
Differences in ground temperatures causes hot and cool spots. Warm air is forced upwards by the cooler air (convection). Rising air parcel goes to lower pressure. Air parcel expands and cools (gas law). If the air parcel is still warmer (buoyant) than the environment, then it will continue to rise. On the other hand, if the air parcel is the same or cooler temperature than the environment, then it will stop rising.
d. Describe the methods of heat transfer by conduction, convection, and radiation, and provide examples for each
Conduction- transfer of energy through matter from one atom/molecules to the next within a substance. Conduction is most effective in solids, but can also take place in fluids. For clarification: the atoms/molecules do not move from one place to another. The energy is transferred by the electrons that are able to move about. An example of conduction is putting a lit match up to a metal needle. The heat is transferred along the needle as the heated electrons gain kinetic energy. The electrons begin to move fast in all directions, colliding with other atoms, passing on heat energy. The atoms, themselves, only vibrate and collide with their neighbors.
Aluminum, bronze, copper, gold, iron are just a few examples of materials that are good conductors.
More Examples:
Ice cube- an ice cube in your hand will eventually melt. The heat is being conducted from your hand into the ice cube.
Ironing- when ironing an item of clothing, the heat from the iron is transferred onto the clothing item.
Convection- heat is transferred in liquids and gases. It is due to the actual motion of the atoms/molecules by movement of currents. If liquid is heated, it expands, becomes less dense, and rises. The cooler, less dense fluid then sinks to take its place. An example of this transfer of heat is by the ocean. During the day, the land heats up faster than the sea. The cooler air over the sea sinks and takes the place of the air over the land, which is warmer (less dense) and rises up in the air. As this air cools over the ocean, it sinks and the cycle continues.
More Examples:
Mantle-The rocky mantle of the earth is slowly moving due to the convection currents that transfers heat from the interior of the Earth towards the surface. This is the reason why the tectonic places are slowly moving around the Earth.
Hot air balloon- The heater inside the balloon heats the air. This warm air moves upward causing the balloon to rise as a result of the hot air trapped inside. In order to descend, you release some of this hot air, allowing cool air to replace it.
Radiation- heat energy in the form of electromagnetic waves is transferred from a hotter to a cooler place without the use of a medium. An example would be the sun. Since there is no large object connecting the Earth and the sun, then conduction cannot take place to bring energy to Earth. In addition, since there is no fluid or gas in space, then convection cannot take place. Thus, the only method in which energy can reach the earth is through electromagnetic waves from the sun.
More Examples:
Microwaves
Radio waves
Campfire's heat- the energy of heat can make light. This light, being a wave, carries energy and moves from one place to another in straight lines. This is the reason that when you are facing the fire, only the front is warmed.
e. Explain how chemical energy in fuel is transformed to heat
Chemical energy is stored in fuel as potential energy and can be released when these compounds undergo chemical reactions. For example, when fuel is burned, the chemical energy is converted to heat energy (exothermic).
The chemical energy in food is converted by the body into mechanical energy and heat.
f. Design and explain experiments to induce a physical change such as freezing, melting, or boiling
http://mypages.iit.edu/~smile/guests/chgstate.htm
http://www.teach-nology.com/teachers/lesson_plans/science/chemistry/reactions/
g. Distinguish between physical and chemical changes and provide examples of each
http://www.learner.org/courses/essential/physicalsci/session4/
http://www.learner.org/courses/essential/physicalsci/session3/
http://www.sciencenetlinks.com/lessons.php?BenchmarkID=4&DocID=402
Physical Change- in a physician change, the chemical composition of the object does not change. If you melt ice, the physical change has occurred (solid substance into a liquid substance, but its chemical composition is still the same (water), H2O).
Chemical Change- in a chemical change, a chemical reaction takes place. The composition of the object changes and we observe a new set of properties; the formation of a new substance. For example, an antacid dropped in a glass of water produces water. A firework displays colorful lights. When a new substance is formed, we usually observe one or more of the following:
- permanent change in color
- odor (gas)
- bubbles (gas released)
- light (energy released)
- heat (energy released)
- formation of solid substance by combining two solutions
1. Frying an egg
2. vaporization of dried ice
3. boiling water
4. burning gasoline
5. baking Cookies
6. souring milk
Answer:
1. Frying an egg ==> Chemical Change
2. vaporization of dried ice ==> Physical Change
3. boiling water ==> Physical Change
4. burning gasoline ==> Chemical Change
5. baking Cookies ==> Chemical Change
6. souring milk => Chemical Change 6. Chemical Change
© Science CSET: Free Prep Guides, 2008. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Science CSET: Free Prep Guides with appropriate and specific direction to the original content.