# THERMAL ENERGY HEAT

Document Sample

```					PHYSIAL SCIENCE

THERMAL ENERGY & HEAT
MRS. JOHNSTON

Heat, Temperature, & Thermal Energy
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Thermal Imaging look at the corporate website

Energy
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Moves from hotter to colder in the form of heat - this is why we feel hot or cold. Usable energy decreases during any process in which energy is transferred. Energy story

Heat Energy
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

 Heat energy (or just heat) is a form of energy which transfers among particles in a substance (or system) by means of kinetic energy of those particle. In other words, under kinetic theory, the heat is transferred by particles bouncing into each other. Heat always refers to the transfer of energy between systems (or bodies), not to energy contained within the systems (or bodies).

Heat -Energy in transit
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Is the transfer of energy from the particles of another object due to a temperature difference. Always from the higher temperature to the lower temperature. Thermal Equilibrium is when the two objects reach the same temperature. Explanation

Measuring Heat
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

The amount of heat or thermal energy transferred from one object to another can be measured in joules, which is the unit of energy. But more often, you see heat measured in calories. A calorie (cal) is the amount of heat required to raise the temperature of 1 gram of of water by 1° C. The relationship between joules and calories is: 1 cal = 4.186 J.

In other words …
THERMAL ENERGY & HEAT
 An object feels warm or hot if its temperature is higher than your skin. To say something is hot means its temperature is relatively high.  Cooling an object is when you are transferring thermal energy from the object from an another object that is at a lower temperature. You could say you are removing thermal energy from your object.  An object feels cool or cold if its temperature is lower than your skin. To say something is cold means its temperature is relatively low.  Whether heating or cooling, the end result is that the two objects become the same temperature after a period of time. This is called thermal equilibrium.

PHYSICAL SCIENCE

Heating and Cooling
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

These systems regulate temperature by transferring energy.
Solar energy

Using Heat
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Any device or process that transfers energy to a substance to raise the temperature of the substance is a heating system. Work can be done to increase temperature. The energy from food is transferred as heat to blood moving throughout the human body.

Heating Systems
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Heated water or air transfers energy as heat in central heating systems. Solar heating also uses warmed air or water Usable energy decreases in all energy transfers. On spacecraft

Cooling
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Device that transfers energy as heat out of an object to lower its temperature is a cooling system. Cooling systems often use evaporation to transfer energy from their surroundings.

Cooling Systems
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Refrigerant is a substance used in cooling systems that transfers large amounts of energy as it changes state. Condensation transfers energy to the surroundings. Heat pumps can transfer energy to or from rooms.

PHYSICAL SCIENCE
THERMAL ENERGY & HEAT

Air Conditioning System

Temperature
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

The measure of how hot or cold something is. A measure of the average kinetic energy of all particles within an object. Instrument used to measure temperature is a thermometer. Experiments –difference between heat and temperature.

Thermometers
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Work because matter expands as it warms up. Fahrenheit and Celsius are common scales used for measuring temperature. The Kelvin scale is based on absolute zero. In the words of Lord Kelvin.

Converting temperatures
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Absolute 0 = 0oK oC g oF = 1.8t + 32.0 oC g K = t + 273 oF g oC = (t – 32.0)/1.8 oF g K = convert to oC then to K

Measuring Temperature
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Measuring water in three scales Freezing Boiling Fahrenheit 32o 212o Celsius 0o 100o Kelvin 273 373 Absolute zero is the temperature at which an objects motion stops. Basis for the Kelvin scale.

Phase Changes
THERMAL ENERGY & HEAT

During a phase change, the temperature remains the same. For freezing and melting
heat = mass in grams x heat of fusion heat =mass in grams x heat of vaporization

PHYSICAL SCIENCE

For boiling and condensation

The heat of fusion of water = 340 J/g The heat of vaporization of water = 2,300 J/g

Particles at Different Temperatures
 Solids THERMAL ENERGY & HEAT
 Particles are bound together in a strong lattice. The individual particles vibrate in fixed positions with respect to each other.
 Particles are loosely bound and are free to move randomly about within the liquid. Occasionally some break free at the surface boundary (evaporation).  Particles are not bound and move freely through out the medium. The average speed is proportional to the temperature of the gas.  Explanation with pictures

PHYSICAL SCIENCE

 Liquids

 Gases

Thermal Energy
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

The motion energy of molecules. The transfer of heat. Thermal energy is the amount of internal kinetic energy and potential energy of an object. It is also simply called internal energy.

Experience Thermal Energy

THERMAL ENERGY & HEAT

1 lb. Coffee Can 3 lb. Coffee Can 1/2 cup Rock salt 1 pint Half and Half 1 1/2 tsps. Vanilla 1/3 cup + 2 tblsps. Sugar For flavored ice cream, choose one: 3 tblsps. of your favorite flavor of instant pudding 1/3 cup of fruit (such as, bananas, strawberries, peaches) 3 of your favorite cookies, crushed into pea-size pieces 1/4 cup finely chopped nuts Mix the first three basic ingredients together and pour into the one pound coffee can. Add flavorings if desired. Place the lid on securely and set inside the three pound can. Add ice, and alternate layers of ice and salt outside the small can and inside the large can. When totally full, secure the lid on the large can. You may wish to add duct tape for good measure. Now here comes the fun part! Place a sheet on the floor or wrap the can in a large towel. Roll the can back and forth for at least 10 minutes. Open the cans and check the ice cream. If it is not starting to freeze, replace lids and roll 10 minutes more. The ice cream should be frozen to the sides and bottom of the can. If not thick enough, place in freezer and check every 10 minutes or so. Serve and enjoy! Yield: 2 cups ice cream

PHYSICAL SCIENCE

Another recipe
THERMAL ENERGY & HEAT
Milk can become ice cream in five minutes! This homemade ice cream in a bag is a summertime delight for kids and adults alike. What you'll need:  1 tablespoon sugar  1/2 cup milk or half & half  1/4 teaspoon vanilla  6 tablespoons rock salt  1 pint-size Ziploc plastic bag  1 gallon-size Ziploc plastic bag  Ice cubes How to make it:  Fill the large bag half full of ice, and add the rock salt. Seal the bag.  Put milk, vanilla, and sugar into the small bag, and seal it.  Place the small bag inside the large one and seal again carefully.  Shake until mixture is ice cream, about 5 minutes.  Wipe off top of small bag, then open carefully and enjoy!

PHYSICAL SCIENCE

Conductors and Insulators
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Conductors - Materials through which energy is easily transferred as heat. Insulators – Materials that conduct energy poorly.

Thermos bottle Insulation

Conductors
THERMAL ENERGY & HEAT Materials through which energy is easily transferred as heat Experiment What is conduction? Conduction is the flow of heat through a solid. When you walk on a hot sidewalk, the concrete warms—or burns—your feet through conduction. When a warmer substance with quickly moving molecules (the sidewalk) comes into contact with a cooler substance with slowly moving molecules (your bare feet), the faster molecules bump into the slower ones and make them move faster, too.

PHYSICAL SCIENCE

Insulation
THERMAL ENERGY & HEAT

Minimizes energy transfer
R value – higher the better Double paned windows – air prevents the transfer of energy description

PHYSICAL SCIENCE

Spacesuit

Energy Efficiency
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Audit your home energy use Home energy checkup Energy games Types of energy Kids site but fun

Energy Transfer
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Thermal energy always moves from hotter to cooler. Methods of energy transfer are:

Explanation Diagrams

Conduction
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Objects must be in direct contact. Objects in contact are at unequal temperatures. Energy is transferred between molecules/ atoms. Ex: Metal rod held over a flame will conduct energy to the opposite end. Definition

Convection
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Transfer of energy by the movement of fluids. (Anything that flows, liquid or gas) Warm air becomes less dense and moves upward. It will be replaced by cooler air that will eventually do the same. Warm rising air will cool, contract, become dense and sink. This cycle is a convection current.

Sea Breeze
THERMAL ENERGY & HEAT

Convection of air

PHYSICAL SCIENCE

Since water gains and loses kinetic energy slowly, the air over land changes temperature faster than over water. During the day the air over land warms faster and rises and is replaced by cool air from the water. During the night the air over the water is warmer than land so it rises and is replaced by air from over the land.

THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Radiation doesn’t require physical contact between objects. Radiation is the transfer of energy by electromagnetic waves. Does not involve the movement of matter. (Hot objects radiate more heat.) Can move through space. Other types of electromagnetic waves include infrared, visible light and ultraviolet rays.

Specific Heat
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Compounds capacity to hold heat. Is the amount of energy transferred as heat that will raise the temperature of 1 kg of a substance by 1 K. Specific heat describes how much energy is required to raise an object’s temperature. Specific heat can change slightly with changing pressure and volume.

Specific Heat Capacity
THERMAL ENERGY & HEAT

PHYSICAL SCIENCE

Heat energy (lost or gained) (J) = mass (g) x change in temperature (TF –Ti) x specific heat (J/kgxoC) Q = m x rt x c

Laws of Thermodynamics
THERMAL ENERGY & HEAT
The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium. Systems tend toward randomness. 2. In any process, the total energy of the universe remains constant. You can’t create it or destroy it. The amount of energy in the universe is constant. 3. As temperature approaches absolute zero, the entropy of a system approaches a constant. This constant actually is zero. 1.

PHYSICAL SCIENCE

Explanation and another Simple explanation Why have them? Another explanation!

2nd Law Another Way
THERMAL ENERGY & HEAT There are other ways to demonstrate how "energy rules." A misguided entrepreneur thought he could raise cats for their fur and use rats as the food source for the cats. He had the bright idea that he would not have to buy food for the rats because the rodents could eat the deskinned cats. Voila! The cats eat the rats and the rats eat the cats. The silly furrier was thinking he was in a closed loop system with nothing being lost, but something was being lost. Energy! Both the cats and rats were emitting heat (and other waste materials) that were not in balance with what was gained from their food sources.

PHYSICAL SCIENCE

Perpetual Motion?
THERMAL ENERGY & HEAT
 A light connected to a solar cell. All the light from the light bulb shines on the solar cell, which makes electricity that goes into the light bulb, which lights the light bulb, and the light shines on the solar cell, and so on.  Would this example work? No, the light will not keep shining because some of the electricity is converted to heat, not light. The solar cell probably doesn't convert all the light to electricity. Some of the electricity is lost in heating the wires between the cell and the bulb. Again the solar cell-light bulb arrangement described above violates the second law of thermodynamics.  (Excerpt taken from KEEP Activity Guide "Energy Sparks.")

PHYSICAL SCIENCE

Review
THERMAL ENERGY & HEAT  Insulation  The Atoms Family  Energy Pioneers –many of these names should sound familiar  Energy review game  Energy experiments  Good review  Measuring energy  Mansfield school review  Quick powerpoint review  Review game

PHYSICAL SCIENCE

```
DOCUMENT INFO
Shared By:
Categories:
Stats:
 views: 4929 posted: 11/11/2009 language: English pages: 37