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thermal equiibrium - answer two objects would not exchange heat or electromagnetic radiation if they were placed in a thermal contact thermal contact - answer two objects are in thermal contact with eachother if energy can be exchanged between them zeroth Law of thermodynamics - answer if objects A and B are separately in equilibrium with a third object C, then A and B are in thermal equilibrium with each other. if two objects have different temperatures, they are not in thermal equilibrium temperature - answer property that determines whether or not energy will transfer between two objects when there is thermal contact only temperatures of A and B will determine if energy will transfer from one to other when placed in thermal contact (not mass, size, material, density, or anything else) Two objects, with different sizes, masses, and temperatures, are placed in thermal contact. In which direction does the energy travel? - answer Answer: Energy travels from the object at a higher temperature to the object at a lower temperature. Explanation: The direction of the transfer of energy depends only on temperature and not on the size of the object or on which object has more mass.
Thermometers are based on principle that some physical property of system changes as system's temperature changes. Here are the 6 principles - - answer 1.) Volume of liquid 2.) Dimensions of solid 3.) Pressure of gas at constant volume 4.) Volume of gas at constant pressure 5.) Electric resistance of conductor 6.) Color of object Celsius - answer -the ice point of water is 0° celsius -the steam point of water is 100° celsius -there are 100 units between these points which are called celsius degrees Fahrenheit - answer -the ice point of water is 32° Fahrenheit -the steam point of water is 212° Fahrenheit -there are 180 units between these points which are called Fahrenheit degrees Kelvin - answer -absolute 0 is 0 Kelvin -triple point of water is 273.16 kelvins -units are kelvins (not degrees kelvin) -size of 1 K unit = 1° celsius unit celsius and kelvin relationship - answer Tc = T - 273. (T: absolute temperature, 0K, cannot be achieved) celsius and fahrenheit relationship - answer Tf = (9/5)Tc + 32°F
On a day when the temperature reaches 50°F, what is the temperature in degrees Celsius and in kelvins? - answer 10°C and 283 K thermal expansion - answer -consequence of change in average separation between atoms in object -as temperature increases, volume increases
- as temperature of solid increases → atoms oscillate with greater amplitudes -average separation between them increases → the object expands thermal expansion/contraction equations - answer ∆L = change in length ∆ T = change in temperature Li = Initial length α = constant (average coefficient of linear expansion) β = constant (average coefficient of volume expansion) A = area V = volume ∆ L/Li = α∆T or ∆L = αLi∆T ∆ A = 2 αAi∆T ∆ V = 3 βVi∆T If you are asked to make a very sensitive glass thermometer, which of the following working liquids would you choose? a.) mercury
b.) alcohol c.) gasoline d.) glycerin - answer Answer: c.) gasoline Explanation: Gasoline has the largest average coefficient of volume expansion. Two spheres are made of the same metal and have the same radius, but one is hollow and the other is solid. The spheres are taken through the same temperature increase. Which sphere expands more? a.) The solid sphere expands more. b.) The hollow sphere expands more. c.) They expand by the same amount. d.) There is not enough information to say. - answer Answer: c.) They expand by the same amount. Explanation: A cavity in a material expands in the same way as if it were filled with the material. A segment of steel railroad track has a length of 30.000m when the temperature is 0.0°C, a.) what is its length when the temperature is 40.0°C? b.) What if the temperature drops to -40.0°C? What is the length of the unclamped segment? - answer a.) using ∆L = αLi∆T, the answer is 30.013m b.) Lf = 30.000m - 0.013m = 22.987m. A poorly designed electronic device has two bolts attached to different parts of the device that almost touch each other in its interior as in the figure. The steel and brass bolts are at different electric potentials, and if they touch, a short circuit will develop, damaging the device. The initial gap between the ends of the bolts is d = 5.0 mm at 27°C. At what temperature will the bolts touch? Assume the distance
T = temperature R = universal gas constant = 8.314 J/(mol×k) = 0.082 L ×atm/(mol×K) Kb = 1.38×10^-23 J/K (Boltzman's constant) N = total number of molecules Na = 6.022 X 10^23 (Avogadro's number) PV = nRT PV = NKbT n = m/M and n = N/Na kb = R/Na A common material for cushioning objects in packages is made by trapping bubbles of air between sheets of plastic. Is this material more effective at keeping the contents of the package from moving around inside the package on a.) a hot day, b.) a cold day, or c.) either hot or cold days? - answer Answer: a.) a hot day Explanation: On a cold day, the trapped air in the bubbles is reduced in pressure according to the ideal gas law. Therefore, the volume of the bubbles may be smaller than on a hot day and the package contents can shift more. A spray can containing a propellant gas at twice atmospheric pressure (202 kPa) and having a volume of 125.00 cm3 is at 22°C. It is then tossed into an open fire. When the temperature of the gas in the can reaches 195°C, what is the pressure inside the can? Assume any change in the volume of the can is negligible. - answer
Answer: Using PV = nRT → PV/T = nR →Pf = (Tf/Ti)Pi → (468K/295K)(202 kPa) = 320 kPa Body A has a higher temperature than body B. Which of the following statements is true? a.) Body A will feel hotter than body B. b.) Body A contains more energy than body B. c.) If places in contact with each other, energy will flow from body A to body B. d.) If placed in contact with a third body having temperature greater than body A, body B will absorb more heat than A. e.) More than one statement is true. - answer Answer: If placed in contact with each other, energy will flow from body A to body B. Explanation: If two bodies of different temperatures are places in thermal contact, heat always flows from the higher-temperature one to the lower-temperature one. Temperature is a measure of... a.) the total amount of heat possessed by something. b.) the flow of energy to or from something. c.) the total energy possessed by something. d.) the total kinetic energy of the constituents of something. e.) the amount of useful work that could be extracted from something. f.) none of the above. - answer Answer: Best choice is none of the above. -temperature is not a description of any other quantity, it is a quantity to itself. -none are accurately a "measure" of temperature.
