Science 10 Mr. Jean April 25 th, 2012. The plan: Video clip of the day Physics test etc… Thermal Energy Thermal Energy Calculations.

Science 10Mr. JeanApril 25th, 2012

The plan: Video clip of the dayPhysics test etcThermal EnergyThermal Energy Calculations

Physics Test People who have not written their science test need to do so.

Alex B, Taylor M, Morgan J, Nathaneal G, Travis S and Alex S.

Color of emission

Solar Energy:

Energy in the Atmosphere:

The process of atmospheric scattering causes rays of sunlight to be redirected to a new direction after hitting a particle in the atmosphere. In this illustration, we see how three particles send light rays off into three different directions. Scattering does not change the striking light ray's wavelength or intensity.

Atmospheric absorption. In this process, sunlight is absorbed by an atmospheric particle, transferred into heat energy, and then converted into long wave radiation emissions that come from the particle.

Atmospheric reflection. In this process, the solar radiation striking an atmospheric particle is redirected back to space unchanged.

Sunlight reaching the Earth's surface unmodified by any of the above atmospheric processes is termed direct solar radiation. Solar radiation that reaches the Earth's surface after it was altered by the process of scattering is called diffused solar radiation. Not all of the direct and diffused radiation available at the Earth's surface is used to do work. As in the atmosphere, some of the radiation received at the Earth's surface is redirected back to space by reflection.

Temperature Scales:What is a thermometer?

Thermometers measure temperature. The first known accurate thermometer was invented about 350 years ago.

Triple Boiling Point of water

James Joule, 1818-1889 Image credit: Wikipedia

How does Energy effect matter?

The point of thermal dynamics (Study of heat energy) is really to do work. We know that heat is really a form of motion in particles and this motion can be used to produce energy.

Heat Engine ConceptAny time a temperature difference exists between two bodies, there is a potential for heat flowExamples:heat flows out of a hot pot of soupheat flows into a cold drinkheat flows from the hot sand into your feetRate of heat flow depends on nature of contact and thermal conductivity of materialsIf were clever, we can channel some of this flow of energy into mechanical work

Heat WorkWe can see examples of heat energy producing other types of energyAir over a hot car roof is lofted, gaining kinetic energyThat same air also gains gravitational potential energyAll of our wind is driven by temperature differencesWe already know about radiative heat energy transferOur electricity generation thrives on temperature differences: no steam would circulate if everything was at the same temperature

How much work can be extracted from heat?Hot source of energyCold sink of energyheat energy delivered from sourceheat energy delivered to sinkexternally delivered work:conservation of energyQ

Lets crank up the efficiencyLets extract a lot ofwork, and deliver very little heat to the sinkIn fact, lets demand 100%efficiency by sending no heatto the sink: all convertedto useful work

Thermal Energy Formula:Q = mcT

Q = Amount of thermal energy (J)m = mass in grams (g)c = Specific heat capacity (J / g)T = Temperature change (C)

Specific Heat Capacities: Each substance has its own specific heat capacity. For example water is 4.18 J/g * C.

Sample Question: If 1g of ethanol is burned to heat 100g of water, raising its temperature by 42K, how many energy was released by the ethanol?

The point of thermal dynamics (Study of heat energy) is really to do work. We know that heat is really a form of motion in particles and this motion can be used to produce energy.

Heat Engine ConceptAny time a temperature difference exists between two bodies, there is a potential for heat flowExamples:heat flows out of a hot pot of soupheat flows into a cold drinkheat flows from the hot sand into your feetRate of heat flow depends on nature of contact and thermal conductivity of materialsIf were clever, we can channel some of this flow of energy into mechanical work

Heat WorkWe can see examples of heat energy producing other types of energyAir over a hot car roof is lofted, gaining kinetic energyThat same air also gains gravitational potential energyAll of our wind is driven by temperature differencesWe already know about radiative heat energy transferOur electricity generation thrives on temperature differences: no steam would circulate if everything was at the same temperature

How much work can be extracted from heat?Hot source of energyCold sink of energyheat energy delivered from sourceheat energy delivered to sinkexternally delivered work:conservation of energyQ

Lets crank up the efficiencyLets extract a lot ofwork, and deliver very little heat to the sinkIn fact, lets demand 100%efficiency by sending no heatto the sink: all convertedto useful work

Try this: Using the table found on page 427 solve the following.

1) How much energy is used to heat 1000g of liquid water by 10 degrees?

2) If we put 1000J of energy into 500g of ethanol how much does it warm up by?

1) How much energy is used to heat 1000g of liquid water by 10 degrees?

2) If we put 1000J of energy into 500g of ethanol how much does it warm up by?