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Review Questions from Textbook: Pg 311 #28, 31, 33, 34, 35, 38, 39, 40, 41, 44, 45, 46, 54, 63, 65, 66, 67
What is the Kinetic Molecular Theory of Matter?
Atoms and molecules that attract each other and vibrate because of kinetic energy. An increase of particle motion makes an object feel warmer and a decrease in particle motion makes the object feel colder.
What was the purpose of Joule's Experiment?
The purpose was to figure out that there's a measurable unit of energy to increase the temperature of water.
How was Joule's experiment performed?
This was done by agitating the water by dropping masses with a measurable energy and watching the change in temperature.
What were the results of Joule's Experiment?
The water increased in temperature and the experiment proves that the energy output can be equated to the energy input.
What is the SI unit for temperature and how does it relate to a Celsius?
The SI unit for temperature is Kelvin (K). TC = TK - 273 and TK = TC + 273
What is the difference between thermal energy and heat?
Thermal energy is the total kinetic and potential energy of molecules. Heat is the transfer of thermal energy.
What type of potential energy do particles experience?
Particles will experience chemical potential energy which is stored in the bonds between atoms and molecules.
What is meant by Absolute Zero and what does it represent?
Absolute zero is when matter has no kinetic energy. It is equal to 0 K° and -273 C°.
Why can no mechanical process be perfectly efficient?
A machine would require itself to create extra input energy to account for any loss, which breaks the first law of thermodynamics. Due to the second law, all machines create small amounts of friction with the air or other molecules and heat will be released and it will eventually run out of energy.
In which direction does thermal energy transfer?
Thermal energy transfers from hot, high-energy molecules to cold, low-energy molecules creating an even distribution of energy
Define temperature and what causes a change in temperature?
Temperature is the average kinetic energy of a molecule. A change in temperature is caused by an increase or decrease in kinetic energy.
What is Conduction?
When two substances touch each other, the fast particles of a warmer material collide with the slow particles of a colder material. This causes the slow particles to speed up and the fast particles to slow down, so the colder object warms up and the warmer object cools down.
What is Convection?
It occurs when colder, denser fluid falls and pushes up warmer, less dense fluid. The colder fluid sinks and pushes up the heated fluid and becomes closer to the heat source repeating the cycle. This is called a convection current, which also forms in gases.
What is Radiation?
A thermal energy transfer that involves electromagnetic waves that are emitted from sources like: lamps, flames, and the Sun. All particles with kinetic energy emit some radiant energy.
Why are conductors of electricity also good conductors of thermal energy?
For something to be a good conductor of electricity, the material needs to have a free flow of electrons which also allows the atoms and molecules to vibrate easily.
What type of energy can be transferred through empty space?
Radiation is the only type of energy that can be transferred through empty space.
What are three ways to heat food or liquids at home.
Putting water in an oven (heats via convection) Putting in a microwave (heats via radiation) Putting water in a pot on a stove (heats via conduction)
What is an insulator?
A material that is unable to transfer electrical/thermal energy well.
What are the three basic concepts of thermal insulation?
Prevent Radiation
Prevent Conduction
Prevent Convection
What is a vacuum flask?
A two-walled bottle that prevents all forms of heat transfer between the inside and outside walls with a vacuum between them.
How does a vacuum flask work?
There is no connection between the two walls which prevents conduction (no transfer of thermal energy). The inside wall is reflective which deflects radiation. Creating a tight seal prevents convection (no air).
What are some home improvements that improve energy efficiency?
Double-paned windows with a vacuum between them. Air-tight doors (seal gaps between rooms) Insulation between walls (fibreglass) High-efficiency furnace
What is the heat capacity and specific heat capacity?
Heat capacity is the amount of thermal energy required to change the temperature of any substance by 1°C/K. Specific heat capacity is the heat capacity of 1.0 kg of a specific substance
How can we measure the quantity of Thermal Energy transferred?
The total amount of thermal energy transferred from a warmer substance to a colder one is the quantity of heat (Q) unit is Joules Q = mcΔT
Explain how the quantity of Thermal Energy (Q) can be both positive and negative.
Q is positive when the material absorbs thermal energy and increases its temperature. Q is negative when it releases thermal energy and decreases its temperature.
What three factors affect the amount of thermal energy transferred?
m = mass (kg) c = specific heat capacity (J/(kg·°C/K)) T = temperature (°C/K), ΔT = Tf - Ti
What is the Principle of Heat Exchange?
Also known as the conservation of energy. When a warmer object touches a colder one, thermal energy is transferred from the warmer object to the colder object until all thermal energy is evenly distributed in both. Q released (neg) + Q absorbed (pos) = 0
How can we measure the specific heat capacity?
Apply the principle of heat exchange to two substances. Use the c value for one substance to calculate energy the energy released/absorbed and use that energy to calculate the c value of the other substance.
What do meteorologists mean by 'wind chill factor'?
Wind Chill factor is the temperature one feels outside when accounting for the wind. Bodies have heat and air molecules remove thermal energy from the body, move away and new molecules do the same. Repeat.
How does energy relate to states of matter and phase transitions?
When an object changes state from solid to liquid, liquid to gas, etc. This is known as a phase change. During phase changes, Temperature does not change. The energy changes forms.
How do kinetic and potential energy change as thermal energy is added?
During the phase change, the average kinetic energy doesn't change and it gets converted to Chemical potential energy in the bonds.
What is the latent heat of fusion and vaporization?
The latent heat of fusion is the amount of thermal energy absorbed when a substance melts and released when it freezes. The latent heat of vaporization is the amount of thermal energy absorbed when it evaporates (boils) and released when it condenses (gas to liquid).
What is the specific latent heat of fusion/vaporization and how can it be found?
The specific latent heat of fusion (Lf) is the thermal energy required to melt/freeze 1 kg of a substance. The specific latent heat of vaporization (Lv) is the thermal energy required to boil/condense 1 kg of a substance. Q = mLf (melting or freezing) Q = mLv (boiling or condensing)
What is a heat pump?
A heat pump exchanges warm air with cold air and vice versa. It takes cold air from outside, heats it up and pumps it inside. It can also take the hot air that rises to the top of the room through a vent and pumps it outside.
How does a refrigerator work?
The high pressure refrigerant is converted into a cold liquid that passes through the walls and absorbs heat. Evaporator coils change the liquid refrigerant into a high pressure gas. A condenser coil converts the gas back into a high pressure liquid, releasing the extra heat through coils, and the cycle repeats.
What classifies a good refrigerant and what are some examples of refrigerants?
A good refrigerant has a low boiling point so it can turn into a gas easily. Some examples are: water (100°C), and Hydrofluorocarbons (Ex: R410A (-48.5°C)).
What is a ground source heat pump and how does it work?
A heat pump that takes water from the surface, puts it deep underground where it can heat up and turn into vapor. The water vapor will rise and can then be used for heating and the cycle repeats.
