Physics Final Exam
Physics Final Exam 1)Heat energy travels from an object with a high temperature to an object with a lower temperature. 2)A substance that heats up relatively quickly has a low specific heat. 3)Heat energy measured in units of calories and joules. 4)Ice has a lower density that water because ice is made of open-structured, hexagonal crystals. 5)Compared to a giant iceberg, a hot cup of coffee has higher temperature, but less internal energy. 6)When a bimetallic bar made of copper and iron strips is heated, the bar bends toward the iron strip. This reason for this is copper expands more than iron. 7)Room temperature on Kelvin scale is about 300K. 8)Some molecules are able to absorb large amounts of energy in the form of internal vibrations and rotations. Materials composed of such molecules have high specific heats. 9)If you measure a plot of land with a brass tape on a cold day, the actual amount of land you have will be larger than measured. 10)Substances absorb heat energy by the process of conduction, radiation and convection. 11)A good heat conductor is a poor insulator. 12)Warm air rises because faster-moving molecules tend to move to regions of less density and pressure. 13)The higher the temperature of an object the shorter the wavelengths it radiates. 14)Newton’s law cooling applies to objects that are heating and cooling. 15)Both black and white road surfaces absorb sunlight. At the end of a sunny day the warmer road surface will be the black surface. 16)Evaporation is a cooling process and condensation is a warming process. 17)Evaporation is a cooling process because the more energetic molecules are able to escape the liquid. 18)When liquids change to a solid state, they release energy. 19)To wholly convert a given amount of heat energy into mechanical energy is impossible regardless of technique used. 20)The first law of thermodynamics is a restatement of the conservation of energy.
Ch. 15 Temperature, Heat, & Expansion • What is the difference between temperature and heat? • Temperature is the measure of the amount of internal energy per particle an object has and heat is total amount of internal energy an object has. • Is there an upper limit on temperature? • No • Is there a lower limit on temperature? • YES! This is called absolute zero and is achieved when all of the heat is removed from a material. • What are the phases of matter? • Solid, liquid, gas, plasma • What are the differences between temperature scales? • F – 32o = freezing; 212o = boiling (for water) This system is based on arbitrary states. • C – 0o = freezing, 100o = boiling (for water). This system is based on the phase changes of water. • K – 0o = absolute zero. Has the same intervals as C (a change in 1o is equivalent in both C and K). This system of based on absolute zero. • How do we quantify heat in terms of energy? • Joules or calories • What does specific heat capacity represent? • The different amounts of heat a material can store. How readily a material can Ch. 16 Heat Transfer • What are the 4 phases of matter?
• Solid, liquid, gas, plasma • What is plasma? • A gas that has so much energy its atoms have become ionized. • Is evaporation make you feel cooler or warmer? • Cooler. Water molecules with more energy (heat) escape leaving behind water with less average energy. • What is sublimation? • Skipping a phase of matter. Going from a solid directly to a gas is an example of sublimation. • What happens to water molecules as they boil? • Water molecules move so fast that they escape the water and become a gas. • What happens to water molecules as they freeze? • Water molecules slow down and organize themselves into a crystal structure known as ice. • What is the heat of fusion? • The amount of energy needed to change a substance from a liquid at its freezing point to a solid and vice versa • What is the heat of vaporization? • The amount of energy needed to change a substance from a liquid at its boiling point to a gas and vice versa. Ch. 18 Thermodynamics According to the 1st law of thermodynamics (on the next slide), if I rub my hands together I am doing work on them. Am I increasing the internal energy of the system?
• Yes. This is why your hands feel warmer. • What is an adiabatic process? • A process in which only work is done on the system and no heat enters or leaves a system. This can be achieved by thermally insulating a system you are doing work on or doing it so fast that heat doesn’t have time to enter or leave the system. • Can you ever have an engine that converts all of its input energy into the same amount of output work? • No! That is because nothing is every 100% efficient as a consequence of the 2nd law of thermodynamics. (Which is listed on the slide after the next one.) • How does the 2nd law of thermodynamics cover that heat flows from warmer to cooler systems to increasing entropy? • Warmer systems have more internal energy, meaning that their particles are moving more than a cooler object. Cooler objects tend to be more organized. Since heat moves from hot to cold, heat also tends to make things less organized. Since entropy is the measure of disorder in a system, the direction
of heat flow also implies an increase in entropy. First Law of Dynamics
-
Conservation of Energy
o
Energy can neither be created nor
destroyed Increase in internal energy + work done by system = Heat added to system Second Law of Dynamics Heat itself never spontaneously flows from a cold object to a hot substance.
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Applied to heat engines
o
When work is done by a heat engine operating between two temperatures, T(hot) and T(cold) only some of the input heat at T(hot) can be converted to work, and the rest is expelled at T(cold)
-
Entropy
o
In natural processes, high-quality energy tends to transform into lower-quality energy – order tends to disorder.
Ch. 15 Temperature, Heat, & Expansion • What is the difference between temperature and heat? • Temperature is the measure of the amount of internal energy per particle an object has and heat is total amount of internal energy an object has. • Is there an upper limit on temperature? • No • Is there a lower limit on temperature? • YES! This is called absolute zero and is achieved when all of the heat is removed from a material. • What are the phases of matter? • Solid, liquid, gas, plasma • What are the differences between temperature scales? • F – 32o = freezing; 212o = boiling (for water) This system is based on arbitrary states. • C – 0o = freezing, 100o = boiling (for water). This system is based on the phase changes of water. • K – 0o = absolute zero. Has the same intervals as C (a change in 1o is equivalent in both C and K). This system of based on absolute zero. • How do we quantify heat in terms of energy? • Joules or calories • What does specific heat capacity represent? • The different amounts of heat a material can store. How readily a material can Ch. 16 Heat Transfer • What are the 4 phases of matter?
• Solid, liquid, gas, plasma • What is plasma? • A gas that has so much energy its atoms have become ionized. • Is evaporation make you feel cooler or warmer? • Cooler. Water molecules with more energy (heat) escape leaving behind water with less average energy. • What is sublimation? • Skipping a phase of matter. Going from a solid directly to a gas is an example of sublimation. • What happens to water molecules as they boil? • Water molecules move so fast that they escape the water and become a gas. • What happens to water molecules as they freeze? • Water molecules slow down and organize themselves into a crystal structure known as ice. • What is the heat of fusion? • The amount of energy needed to change a substance from a liquid at its freezing point to a solid and vice versa • What is the heat of vaporization? • The amount of energy needed to change a substance from a liquid at its boiling point to a gas and vice versa. Ch. 18 Thermodynamics According to the 1st law of thermodynamics (on the next slide), if I rub my hands together I am doing work on them. Am I increasing the internal energy of the system?
• Yes. This is why your hands feel warmer. • What is an adiabatic process? • A process in which only work is done on the system and no heat enters or leaves a system. This can be achieved by thermally insulating a system you are doing work on or doing it so fast that heat doesn’t have time to enter or leave the system. • Can you ever have an engine that converts all of its input energy into the same amount of output work? • No! That is because nothing is every 100% efficient as a consequence of the 2nd law of thermodynamics. (Which is listed on the slide after the next one.) • How does the 2nd law of thermodynamics cover that heat flows from warmer to cooler systems to increasing entropy? • Warmer systems have more internal energy, meaning that their particles are moving more than a cooler object. Cooler objects tend to be more organized. Since heat moves from hot to cold, heat also tends to make things less organized. Since entropy is the measure of disorder in a system, the direction
of heat flow also implies an increase in entropy. First Law of Dynamics
-
Conservation of Energy
o
Energy can neither be created nor
destroyed Increase in internal energy + work done by system = Heat added to system Second Law of Dynamics Heat itself never spontaneously flows from a cold object to a hot substance.
-
Applied to heat engines
o
When work is done by a heat engine operating between two temperatures, T(hot) and T(cold) only some of the input heat at T(hot) can be converted to work, and the rest is expelled at T(cold)
-
Entropy
o
In natural processes, high-quality energy tends to transform into lower-quality energy – order tends to disorder.
