Physics: Heat Assessment
Radiation
- the transfer of thermal energy by electromagnetic radiation - does not require a medium
Units for measuring energy
joules calories BTUs
Metal Specific Heat Metal Specific Heat aluminum 900 J/kgC° mercury 140 J/kg.C° copper 385 J/kg.C° sand 664 J/kg.C° Which substance would require the most heat to raise the temperature of 1,000 g 1°C? A. aluminum B. mercury C. copper D. sand
aluminum
1 calorie equals...
= 0.001 kcal = 4.186J
1 Joule equals...
= 0.239 cal = 0.000239 kcal
1 kcal equals...
= 1,000 cal = 4186
1 kcal is
Calorie (Cal), or dietary calorie
Which two temperature scales are a US scientist most likely to use in his or her work? A. Fahrenheit and Kelvin B. Fahrenheit and Celsius C. Celsius and Kelvin D. Kelvin and joule
Celsius and Kelvin
temperature scales
Fahrenheit, Celsius, and Kelvin
Which of the following correctly describes heat? A. Heat is thermal energy flowing from a lower temperature object to a higher temperature object. B. Heat is thermal energy flowing from a higher temperature object to a lower temperature object. C. The total heat contained in an object is the same as its temperature. D. Heat is the total amount of energy associated with an object.
Heat is thermal energy flowing from a higher temperature object to a lower temperature object.
Heat
a measure of thermal energy in transit
objects that have different masses and/or different specific heats
may require different amounts of thermal energy to reach the same temperature
Increased kinetic energy increases the temperature, except at _____________. In this case, the temperature is __________ while the ___________ is accomplished.
phase-change points constant phase change
example of radiation
the warmth felt near a hot fire
Convection is the transfer of ________ along with moving matter. A. thermal energy B. radiation C. phase changes D. specific heat
thermal energy
Heat transfers energy until __________ is reached.
thermal equilibrium
The specific heat of a material is the amount of energy required A. to induce a phase change in the material. B. to bring the material to 0°C. C. to move it with a force of 1 N over a distance of 1 m. D. to change 1 g of the material by 1°C or 1 K.
to change 1 g of the material by 1°C or 1 K.
example of conduction
heating one end of an iron bar. Soon, the other end of the bar becomes hot
If one end of an iron bar is heated, what causes thermal energy to transfer to the other end? A. convection B. conduction C. radiation D. heat of fusion
conduction
At the phase-change points, the temperature remains _________ until the _________ is complete.
constant phase change
The SI unit of measure for thermal energy is a A. calorie B. joule C. BTU D. degree Celsius
joule
The common units used to measure thermal energy
joules (J) and calories (cal)
As energy is added to a substance, either the _______________ or ________________.
kinetic energy of its particles increases a phase change happens
The "kcal" unit is A. a kilogram calorie B. 1,000 calories C. 0.001 calories D. different from a dietary calorie
1,000 calories
Larger units of kilojoules (kJ) and kilocalories (kcal) are also used. They are_________ times larger than joules and calories, respectively.
1000
Which tool would be used to measure the changes in thermal energy of an object? A. hydrometer B. calorimeter C. specific heat meter D. can't measure it
calorimeter
Metal Specific Heat Metal Specific Heat aluminum 900 J/kgC° mercury 140 J/kg.C° copper 385 J/kg.C° sand 664 J/kg.C° One substance gave off 2695 J of heat when a 1,000. g mass of it had its temperature lowered by 7.0°C. This substance was A. aluminum B. mercury C. copper D. sand
copper
Which of the following is not a unit of energy? A. degree Celsius B. calorie C. kilocalorie D. joule
degree Celsius(it's a unit of temperature)
The flow of thermal energy from an object at a high temperature to one at low temperature is called . A. potential energy B. heat C. work D. temperature
heat
Thermal energy flows from________ temperature to__________ temperature.
higher lower (No process allows the reverse without work being done in an isolated system.)
Thermal energy
the total kinetic energy of the particles that make up a substance
example of convection
the upward flow of air above a room heater
The total energy of the particles that make up an object is A. kinetic energy B. temperature C. thermal energy D. specific heat
thermal energy
Explain the difference between thermal energy and temperature.
thermal energy = total KE (adding it changes temp or state) temperature =average KE
Which of the following cannot be the only movement of thermal energy in an isolated system? A. thermal energy transferred from a hotter object to a colder object B. thermal energy transferred from a colder object to a hotter object C. thermal energy transferred from one object to another D. temperature changes among the system's objects
thermal energy transferred from a colder object to a hotter object
In the context of heat, radiation is the transfer of ________ by ________. A. heated fluids; convection B. molecular kinetic energy; conduction C. heat; phase changes D. thermal energy; electromagnetic radiation
thermal energy; electromagnetic radiation
The warmth felt next to a hot fire is mainly due to ________. A. convection of air heated by the fire B. thermal radiation emitted by the fire C. conduction of heat through the air D. the visible radiation changing to heat as it shines on surfaces
thermal radiation emitted by the fire
The specific heat of a material is the amount of energy required A. to induce a phase change in the material. B. to bring the material to 0°C. C. to move it with a force of 1N over a distance of 1m. D. to change 1g of the material by 1°C or 1K.
to change 1g of the material by 1°C or 1K.
Thermal energy is transferred by
transferred by conduction, convection, and radiation
To solve calorimetry problems
use the principle of the conservation of energy in an isolated system and the specific heat equation Q = mcΔT.
Which of the following can cause objects to require different amounts of thermal energy to reach the same temperature? A. different materials B. different specific heats C. different masses D. all of the above
all of the above
An object with a specific heat of 525 J/kg.C° goes through a temperature change of 5°C. What additional information would you need to calculate the change in thermal energy? A. initial temperature of the object C. mass of the object B. final temperature of the object D. volume of the object
mass of the object
Metal Specific Heat Metal Specific Heat aluminum 900 J/kgC° mercury 140 J/kg.C° copper 385 J/kg.C° sand 664 J/kg.C° Fifty grams of each substance are placed in an oven. After 15 minutes of heating, which substance would go through the greatest temperature change A. aluminum B. mercury C. copper D. sand
mercury
Thermal energy is being steadily added to a system. Which two effects do not occur at the same time? A. change of state and phase change B. average kinetic energy increase and temperature increase C. phase change and temperature increase D. total kinetic energy increase and phase change
phase change and temperature increase
Thermal energy is being steadily added to a system. Which two effects do not occur at the same time? A. change of state and phase change B. average kinetic energy increase and temperature increase C. phase change and temperature increase D. total kinetic energy increase and phase change
phase change and temperature increase
One calorie is the amount of energy required to ________. A. exert a force of 1 N over a distance of 1 m B. raise the temperature of 1 kg of water by 1°C C. raise the temperature of 1 g of water by 1°C D. change the state of matter of 1 g of water
raise the temperature of 1 g of water by 1°C
One calorie is the amount of energy required to________. A. exert a force of 1N over a distance of 1m B. raise the temperature of 1 kg of water by 1°C C. raise the temperature of 1 g of water by 1°C D. change the state of matter of 1 g of water
raise the temperature of 1 g of water by 1°C
Adding thermal energy to a substance either increases its________ or changes its_________.
temperature state
Specific heat
the amount of energy required to raise the temperature of 1 g of the material by 1ºC
Which physical principle is the main foundation for solving thermal energy transfer problems for a particular system? A. the law of conservation of energy B. mass balancing C. conservation of temperature D. temperature averaging
the law of conservation of energy (the first law of thermodynamics)
Calorimetry
the study of the thermal-energy transfer between different substances
Calorimetry is ________. A. changing calories into metric units B. the measurement of heat imparted to substances from calorimeters C. the study of thermal energy exchange during thermodynamic processes D. the comparison of calories with the amount of heat represented by other units
the study of thermal energy exchange during thermodynamic processes
Which of the following correctly describes heat? A. when the substance is in it gaseous state B. when the substance is undergoing a phase change C. when it has reached its specific heat capacity D. when its molecules are gaining kinetic energy
when its molecules are gaining kinetic energy
When does the flow of thermal energy stop? A. when the objects are in thermal equilibrium B. when all the thermal energy has transferred to the cooler object C. when the cooler object cannot absorb more thermal energy D. when the objects have both changed temperature by the same amount
when the objects are in thermal equilibrium
When does the flow of thermal energy stop? A. when the objects are in thermal equilibrium B. when all the thermal energy has transferred to the cooler object C. when the cooler object cannot absorb more thermal energy D. when the objects have both changed temperature by the same amount
when the objects are in thermal equilibrium
Under what conditions does thermal-energy transfer between objects at different temperatures?
- The objects must be in thermal contact. - Hot to cold
Temperature
- a measure of the average kinetic energy of the particles in a substance - tells how "hot" or "cold" something is
Convection
- energy transfer by moving matter - works with fluids (liquids and gases). - does not work in a vacuum
0.239 cal is equivalent to ________. A. 1 J B. 239 kcal C. 1 kJ D. 239 J
1 J
Which of the following can cause objects to require different amounts of thermal energy to reach the same temperature? A. different materials B. different specific heats C. different masses D. all of the above
all of the above
Thermal energy added during a phase change
allows the particles to overcome the intermolecular forces holding them together instead of increasing their kinetic energy
Conduction
- happens within a substance - Energy applied to one area moves to other areas - Particles transfer kinetic energy by way of collisions - works best with solids - works less well with liquids and not well with gases - It does not work in a vacuum.
Explain how putting a block of metal and a block of wood in the freezer is an example of heat. Even though they would both eventually reach the same temperature, the metal would cool down faster - explain why. If you grabbed them both out of the freezer after they were the same temperature, the metal would feel "colder" - explain why?
-2 things of different temperatures coming into contact and exchanging heat(def. of heat) -metals have lower specific heat -metals are conductors (heat flows in and out faster)
0.239 cal is equivalent to________. A. 1 J B. 239 kcal C. 1 kJ D. 239 J
1 J
The energy required to raise the temperature of 1 kg of water by 1°C is A. 1 J. B. 1 K. C. 1 cal. D. 1 kcal.
1 kcal.
The "kcal" unit is A. a kilogram calorie B. 1,000 calories C. 0.001 calories D. different from a dietary calorie
1,000 calories
The emission and absorption of electromagnetic radiation results in the transfer of thermal energy. The best example of this is ________. A. a microwave oven B. a pot sitting on a stovetop burner C. a convection space heater D. a fan
a microwave oven
The SI unit of measure for thermal energy is a A. therm B. joule C. BTU D. degree Celsius
joule
A=200g and 50˚C B=200g 70˚C C=400G 70˚C Assuming beakers A, B and C all contain pure water, which beaker contains water molecules with the greatest average kinetic energy? A. beaker A B. beaker B & C C. beaker C D. the average kinetic energy is equal in all three
beaker B & C
Which of the following is the best example of convection? A. hot air naturally flowing upward above a heater B. the handle end of a metal spoon in a pot of boiling water becoming hot C. the warmth felt next to a lit incandescent light bulb D. a black asphalt driveway becoming hot in the Sun
hot air naturally flowing upward above a heater
During a phase change, as energy is added, the temperature of a substance ________. A. increases B. is constant C. decreases D. first increases and then decreases to its original value
is constant
During a phase change, as energy is added, the temperature of a substance ________. A. increases B. is constant C. decreases D. first increases and then decreases to its original value
is constant
When energy is added to a substance at constant volume and pressure, its temperature increases except ________. A. when the substance is in it gaseous state B. when the substance is undergoing a phase change C. when it has reached its specific heat capacity D. when its molecules are gaining kinetic energy
when the substance is undergoing a phase change