Kelvin is an important scale used in most of science. The ... Web viewWater freezes at the value 273.15 and boils at 373.15 Kelvin. The word "Kelvin" comes from Lord Kelvin, who did

UNIT 3A STUDY REFERENCEENERGYLAGRECA SCIENCE

UNIT 3a STUDY REFERENCE-ENERGY

UNIT 3a-6.P.3-Understand characteristics of energy transfer and interactions of matter and energy

Part 1: 6.P.3.1-Energy Transfer-Illustrate the transfer of heat energy from warmer objects to cooler ones using examples of conduction, radiation, and convection the effects that may result

Heat and Thermal Energy

When scientists originally studied thermodynamics, they were really studying heat and thermal energy. Heat can do anything: move from one area to another, get atoms excited, and even increase energy. Did we say energy? That's what heat is. When you increase the heat in a system, you are really increasing the amount of energy in the system. Now that you understand that fact, you can see that the study of thermodynamics is the study of the amount of energy moving in and out of systems.

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Heat of Atoms

Now all of this energy is moving around the world. You need to remember that it all happens on a really small scale. Energy that is transferred is at an atomic level. Atoms and molecules are transmitting these tiny amounts of energy. When heat moves from one area to another, it's because millions of atoms and molecules are working together. Those millions of pieces become the energy flow throughout the entire planet.

Temperature- average kinetic energy of an object’s molecules. The more kinetic energy molecules have, the higher the temperature.

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Heat Movement

Heat moves from one system to another because of differences in the temperatures of the systems. If you have two identical systems with equal temperatures, there will be no flow of energy. When you have two systems with different temperatures, the energy will start to flow. Air mass of high pressure forces large numbers of molecules into areas of low pressure. Areas of high temperature give off energy to areas with lower temperature. There is a constant flow of energy throughout the universe. Heat is only one type of that energy.

Energy Likes to Move

If there is a temperature difference in a system, heat will naturally move from high to low temperatures. The place you find the higher temperature is the heat source. The area where the temperature is lower is the heat sink.

Energy can be transferred from one system to another in different ways:

1. Thermally-when a warmer object is in contact with a cooler object2. Mechanically-when two objects push or pull on each other over a distance3. Electrically-when an electrical source such as battery or generator is

connected in a complete circuit to an electrical device4. By electromagnetic waves, as light travels

Thermal energy

Thermal energy is transferred through a material by the collision of atoms within the material. Heat flows through the material from warm objects to cooler objects, until both objects are at equilibrium.

Heat travels through solids by a process called conduction, of two objects touching each other

Heat travels through liquids and gases through convection.

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Heat travels in the form of electromagnetic radiation through radiation.

Ever Hear of Convection Ovens?

Convection is the way heat is transferred from one area to another when there is a "bulk movement of matter." It is the movement of huge amounts of material, taking the heat from one area and placing it in another. Warm air rises and cold air replaces it. The heat has moved. It is the transfer of heat by motion of objects. Convection occurs when an area of hot water rises to the top of a pot and gives off energy. Another example is warm air in the atmosphere rising and giving off energy. They are all examples of convection. The thing to remember is that objects change position.

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Radiating Energy

When the transfer of energy happens by radiation, there is no conductive medium (such as in space). That lack of medium means there is no matter there for the heat to pass through. Radiation is the energy carried by electromagnetic waves (light). Those waves could be radio waves, infrared, visible light, UV, or Gamma rays. Heat radiation is usually found in the infrared sections of the EM spectrum. If the temperature of an object doubles (in Kelvin), the thermal radiation increases 16 times. Therefore, if it goes up four times, it increases to 32 times the original level.

Scientists have also discovered that objects that are good at giving off thermal radiation are also good at absorbing the same energy. Usually the amount of radiation given off by an object depends on the temperature. The rate at which you absorb the energy depends on the energy of the objects and molecules surrounding you.

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Conducting Energy and Heat

Conduction is a situation where the heat source and heat sink are connected by matter. As we discussed before, the heat flows from the source down the temperature gradient to the sink. It is different from convection because there is no movement of large amounts of matter, and the transfers are through collisions. The source and the sink are connected.

If you touch an ice cream cone, the ice cream heats up because you are a warmer body. If you lie on a hot sidewalk, the energy moves directly to your body by conduction. When scientists studied good thermal radiators, they discovered that good thermal conductors are also good at conducting electricity. So when you think of a good thermal conductor, think about copper, silver, gold, and platinum.

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Getting Hotter = Getting Bigger

Now you need to think about states of matter a little bit. We'll start with gases. The idea behind thermal expansion is that gases expand as the temperature increases. If you have a balloon and you heat up the contents, the balloon will get larger. Scientists use the term ideal gas law to describe this activity.

Liquids expand and contract, too, but there is a lot less change than in gases. Scientists say they have a smaller thermal expansion coefficient. As you can probably figure out, solids expand and contract the least of all the states of matter. The expansion coefficient is different for each piece of matter. It is a unique value, just like specific heat capacity. Two examples of coefficients are air at .00367 and alcohol at .000112.

Things Shrink When They get Cold

The opposite of expansion is contraction. If things expand with the addition of heat, it makes sense that they contract when heat is removed. If you remove enough heat from a gas it will become a liquid. Liquids can turn into solids with further cooling. What happens when you remove almost all of the energy from a system? Scientists use the terms absolute zero to describe a system that has no kinetic energy. When there is no kinetic energy in a system, all molecular motion

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stops. It seems that even the atoms begin to merge at these low temperatures. Physicists have recently created the Bose-Einstein state of matter that has a small group of atoms with nearly all of the kinetic energy taken out of the system

More Transfer of Energy

Heat is the thermal energy transported from one system to another because of a temperature difference. The transfer of that energy stops when the temperature balances out in the entire environment. Scientists use the unit of a calorie to measure heat. You might be saying, "I've heard of calories. Are those like the ones in food?" The answer is "Yes." One calorie is measured as the amount of energy needed to raise the temperature of one gram of water, one degree Celsius. When you “burn” food (this happens VERY slowly in your body), you release energy.

Three Big Temperature Scales

Since we're going to be talking about heat, temperatures, and energy, we wanted to introduce you to how temperature is measured. The big three are Fahrenheit, Celsius and Kelvin. Even though scientists may use only a few scales to measure temperature, there are dozens of types of devices that measure temperatures. All of these devices are called thermometers because they measure temperature. There are thermometers to measure your body temperature, the temperature in your oven, and even the temperature of liquid oxygen.

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Fahrenheit is the Classic

Fahrenheit is the classic English system of measuring temperatures. Water freezes at 32 degrees Fahrenheit and boils at 212 degrees. The scale was created by Gabriel Daniel Fahrenheit in 1724 and divides the difference between the boiling point and freezing point of water into 180 equal degrees. You will probably be asked to convert temperatures back and forth from Fahrenheit to Celsius. Here's the formula: (Fahrenheit-32)*5/9=Celsius.

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Celsius Based on Water

Celsius is the modern system of measuring temperature. It fits in with much of the metric system and has nice round numbers. In Celsius, we call the freezing point of water 0 degrees Celsius, and the boiling point 100 degrees Celsius. Then the scale is divided into 100 equal degrees between those two points. The scale used to be known as centigrade but the name was changed several years ago. Both Celsius and Fahrenheit are used when discussing our day-to-day weather temperatures. Celsius degrees are larger than Fahrenheit degrees.

Kelvin to Absolute Zero

Kelvin is an important scale used in most of science. The big difference is that it is based on a single point (absolute zero) which is given a value of 0 degrees. From there, the scale increases by degrees that are the same size as Celsius degrees. It is a scale that is based on energy content, rather than on arbitrary temperature

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values like the other two scale (based on water). Water freezes at the value 273.15 and boils at 373.15 Kelvin. The word "Kelvin" comes from Lord Kelvin, who did a lot of work with temperatures.

Thermodynamic Laws that Explain Systems

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A thermodynamic system is one that interacts and exchanges energy with the area around it. The exchange and transfer need to happen in at least two ways. At least one way must be the transfer of heat. If the thermodynamic system is "in equilibrium," it can't change its state or status without interacting with its environment. Simply put, if you're in equilibrium, you're a "happy system," just minding your own business. You can't really do anything. If you do, you have to interact with the world around you.

A Zeroth Law?

The zeroth law of thermodynamics will be our starting point. We're not really sure why this law is the zeroth. We think scientists had "first" and "second" for a long time, but this new one was so important it should come before the others. And voila! Law Number Zero! Here's what it says: When two systems are sitting in equilibrium with a third system, they are also in thermal equilibrium with each other.

In English: systems "One" and "Two" are each in equilibrium with "Three." That means they each have the same energy content as "Three". But if THAT’S true, then all the values found in "Three", match those in both "One" and "Two". It’s obvious, then, that the values of "One" and "Two" must ALSO match. This means that "One" and "Two" have to be in equilibrium with each other.

A First Law

The first law of thermodynamics is a little simpler. The first law states that when heat is added to a system, some of that energy stays in the system and some leaves the system. The energy that leaves does work on the area around it. Energy that stays in the system creates an increase in the internal energy of the system.

In English: you have a pot of water at room temperature. You add some heat to the system. First, the temperature and energy of the water increases. Second, the system releases some energy and it works on the environment (maybe heating the air around the water, making the air rise).

A Second Law

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The big finish! The second law of thermodynamics explains that it is impossible to have a cyclic (repeating) process that converts heat completely into work. It is also impossible to have a process that transfers heat from cool objects to warm objects without using work.

In English: that first part of the law says no reaction is 100% efficient. Some amount of energy in a reaction is always lost to heat. Also, a system can not convert all of its energy to working energy.

The second part of the law is more obvious. A cold body can't heat up a warm body. Heat naturally wants to flow from warmer to cooler areas. Heat wants to flow and spread out to areas with less heat. If heat is going to move from cooler to warmer areas, it is going against what is “natural”, so the system must put in some work for it to happen.

Part 2: 6.P.3.3-Technological Design-Explain the sustainability of materials for use in technological design based on a response to heat (to include conduction, contraction, expansion) and electrical energy

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UNIT 3a-ENERGY VOCAB

6.P.3.1-Energy Transfer

Energy-the ability to cause changes

Kinetic energy-energy of motion

Potential energy-stored energy

Heat-the transfer of thermal energy from one object to another when the objects are at different temperatures

Temperature-average kinetic energy of an object’s molecules. The more kinetic energy molecules have, the higher the temperature.

Thermal-relating to heat, like a thermal sweater, thermal cup

Thermal energy-energy due to the motion of particles in matter

Degree-a unit of measurement, such as temperature

Farhrenheit- the classic English system of measuring temperatures. Water freezes at 32 degrees Fahrenheit and boils at 212 degrees.

Celsius- the modern system of measuring temperature. It fits in with much of the metric system and has nice round numbers.

Heat flow-the transfer of energy from a warmer object to a cooler object. The molecules in the warm object give the energy to the

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molecules in the cold object. This process continues until all the molecules are at the same temperature

The place you find the higher temperature is the heat source. The area where the temperature is lower is the heat sink

Equilibrium- The point of heat transfer when all the molecules are at the same temperature

Conduction-is a situation where the heat source and heat sink are connected by matter. Heat flows from the source down the temperature gradient to the sink. It is different from convection because there is no movement of large amounts of matter, and the transfers are through collisions. The source and the sink are connected.

Convection-is the way heat is transferred from one area to another when there is a "bulk movement of matter." It is the movement of huge amounts of material, taking the heat from one area and placing it in another. Warm air rises and cold air replaces it. The heat has moved. It is the transfer of heat by motion of objects.

Radiation-Energy that is transferred through electromagnetic waves. When the transfer of energy happens by radiation, there is no conductive medium (such as in space). That lack of medium means there is no matter there for the heat to pass through. Radiation is the energy carried by electromagnetic waves (light). Those waves could be radio waves, infrared, visible light, UV, or Gamma rays. Heat radiation is usually found in the infrared sections of the EM spectrum.

6.3.3.3-Technological design

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http://www.physics4kids.com/files/light_emtype.html


Expansion-the expanding of molecules as the temperature increases or an object is heated

Contraction-the opposite of expansion, that occurs when temperature decreases or an object is cooled

Conductor-a material that is good at transferring heat, where the thermal energy flows easily. Example is a hot spoon since the heat is spread throughout the spoon

Insulator-a material that is not good at transferring heat, where thermal energy doesn’t flow easily. Example is wood since the heat is not spread throughout the wood

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Documents

Kelvin is an important scale used in most of science. The ... Web viewWater freezes at the value 273.15 and boils at 373.15 Kelvin. The word "Kelvin" comes from Lord Kelvin, who did