Thermal Energy. Thermal Energy is the TRANSFER of kinetic energy between two objects that are at different temperatures.

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1 Thermal Energy Thermal Energy is the TRANSFER of kinetic energy between two objects that are at different temperatures. And remember: heat will always transfer from a warm object to a cold object. HEAT When does heat transfer stop?

2 Kinetic Theory of Matter ALL matter is made up of MOVING particles Those particles have KINETIC and POTENTIAL ENERGY Particles bounce off each other, creating FRICTION (remember the 4 types we learned). This changes the kinetic and potential energy into THERMAL ENERGY

3 Thermal Energy * All matter is made of particles that are always in random motion * Thermal Energy is the TOTAL kinetic energy of the particles within a substance * The more of the substance there is, the higher the thermal energy Energy is created when the molecules inside of a substance bump into each other, creating friction.

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5 Put these things in order from most thermal energy to least thermal energy. a cup of ice water a swimming pool a cup of boiling hot water the Atlantic Ocean

6 Temperature Temperature is a measure of the AVERAGE kinetic energy of the particles within an object. In simple terms, the temperature of an object depends on the average kinetic energy of the moving particles within a substance. If the molecules in a substance are moving slower, the object will feel cooler. If the molecules in a substance are moving faster, the object will feel warmer.

7 THERMOMETER Thermometers are the instrument used to measure temperature January 09, 2013

8 Three different temperature scales Fahrenheit - based on the lowest temperature achieved with a salt water mixture. - the increments are called degrees Fahrenheit Celsius - based on the boiling and freezing point of water - divided into 100 equal parts called degrees Celsius (centigrade) Kelvin - based on ABSOLUTE ZERO - the point at which all molecular movement stops - degrees are called 'kelvins' (K), which are the same size as Celsius degrees

9 COMPARING THE 3 SCALES WHY WOULD A DOCTOR WORRY ABOUT A PATIENT WITH A FEVER OF A COUPLE OF DEGREES HIGHER THAN NORMAL CELSIUS RATHER THAN FAHRENHEIT?

10 THERMAL EQUILIBRIUM thermal equilibrium is when the heat transfer stops because the substances have reached the same temperature. a lack of heat energy is referred to as COLD

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12 CONDUCTION - heat transfer through direct contact Conduction is the reason it isn't a good idea to leave the spoon in the pot of soup! It is also the reason that food cooks in a frying pan.

13 Convection - when heat is transferred through a fluid (gas or liquid) the warm fluid rises forcing the cooler fluid downward.

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15 CONVECTION A B C

16 Radiation - heat transfer through space caused by electromagnetic waves.

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18 LAMP SILVER BLACK

19 THERMAL EXPANSION Thermal expansion is the increase in volume of a substance due to its increase in temperature Alcohol thermometer: As the temp. of the alcohol rises, the molecules move faster and spread out.

20 THERMAL CONTRACTION The decrease in volume of an object due to a decrease in temperature. Most objects contract if they cool off. This means that the spaces in between the sidewalks will grow wider when its temperature drops.

21 Mother Nature was SMART!! But that means water is weird! Water expands and floats (takes up more space per unit more volume--less dense!) Density of water 1.0 g/cm³ Density of ice 0.9 g/cm³ Ice forms on TOP of a pond. It insulates the water below, allowing wildlife to live through the winter. If it did not float, ponds would fill with ice, killing all plant and animal life!

22 CONDUCTORS and INSULATORS of heat CONDUCTOR is an object that easily transfers heat. Ex: metals INSULATOR is an object that does not easily transfer heat. Ex: rubber, wood, plastic, water BIMETALIC STRIP DEMO

23 SPECIFIC HEAT is a substance's unique ability to absorb (take in) or release (give off) heat. It is the amount of energy needed to change the temperature of one gram of a substance by 1º Celsius We will use calories as the unit of measure for heat energy Raise 1 g by 1º C = 1calories

24 The lower the specific heat of a material the better a conductor it is. For example, copper is a great conductor (specific heat =.09) Wood is a good insulator (specific heat =.41) Which means the lower the specific heat the better it transfers thermal energy. METAL FINGERS DEMO

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26 Specific Heats of common materials: Water 1 cal/g ºC Ice.5 cal/g ºC Steam.5 cal/g ºC Copper.09 cal/g ºC Aluminum.22 cal/g ºC Iron.11 cal/g ºC

27 Formula for calculating heat energy using specific heat Q = m C T = x x Thermal Energy (cal) mass Specific Heat Change in Temperature Q = heat energy gained or lost (in calories) m = mass (g) C = specific heat (cal/g ºC) T = change in Temp (ºC)

28 Try this... A B What is the energy required to raise the temperature of 100 g steel seatbelt from 75º C to 100º C? What is the energy required to raise the temperature of 100 g seatbelt cloth from 75º C to 100º C? Q = m C T Metal of seatbelt Cloth of seatbelt 0.12 cal/gºc 0.31 cal/gºc

29 Energy for the metal Q = mc T Q = (100g)(0.12 cal)(25º C) gºc Q = 300 cal Energy for the cloth Q = mc T Q = (100 g)(0.31 cal)(25º C) gºc Q = 775 cal The metal and the cloth need different amounts of energy to make the same temperature change. This is due to each substance's unique specific heat.

30 PUT THE FOLLOWING LABELS ON THE DIAGRAM: MOST DENSE LEAST DENSE MOST KINETIC ENERGY LEAST KINETIC ENERGY HIGHEST TEMPERATURE LOWEST TEMPERATURE LEAST DENSE MOST DENSE LEAST KINETIC ENERGY MOST KINETIC ENERGY LOWEST TEMP. HIGHEST TEMP.