AP PHYSICS 2 WHS-CH-14 Heat Show all your work, equations used, and box in your answers! 1 108kg

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1 AP PHYSICS 2 WHS-CH-4 Heat Show all your work, equations used, and box in your answers! James Prescott Joule (88 889) James Prescott Joule studied the nature of heat, and discovered its relationship to mechanical work. Multiple Choice How much heat is required to raise the temperature of a 0.04 kg stainless steel spoon from 20 o C to 50 o C if the specific heat of stainless steel is 0.50 KJ/kg x o C? (A) 200 J (B) 400 J (C) 600 J (D) 800 J (E),000 J The melting point of copper is,080 o C and its heat of fusion is 200 KJ/kg. If a copper coin at this temperature is completely melted by the absorption of 2,000 J of heat, what is the mass of the coin? (A), 080kg (B) 540kg (C) 08kg (D) 00kg (E) 50kg Water has the specific heat 4.86 KJ/Kg. o C, a boiling point of 00 o C, and a heat of vaporization of 2,260 KJ/kg. A sealed beaker contains 00 g of water that s initially at 20 o C. If the water absorbs 00 KJ of heat, what will its final temperature be? (A) 00 o C (B) 9 o C (C) 43 o C (D) 83 o C (E) 239 o C On a cold winter day (5 o C), the foundation block for a statue is filled with 2.0 m 3 of concrete. By how much will the concrete s volume increase on a very warm summer day (35 o ) if its coefficient of volume expansion is 4.0 x 0-5 / o C? (A) 60 cm 3 (B),200 cm 3 (C),600 cm 3 (D) 2,400 cm 3 (E) 3,200 cm 3 A thermally-isolated system is made up of a hot piece of aluminum and a cold piece of copper, with the aluminum and copper in thermal contact. The specific heat capacity of aluminum is more than double that of copper. Which object experiences the greater magnitude of gain or loss of heat during the time the system takes to reach thermal equilibrium? (A) Aluminum (B) Copper (C) Neither, because both undergo the same magnitude of gain or loss of heat (D) Requires knowing the mass As a solid goes through a phase change to a liquid, heat is absorbed and the temperature: (A) fluctuates (C) decreases (B) remains the same (D) increases

2 Objects and 2 are heated from the same initial temperature (Ti) to the same final temperature (Tf). Object has three times the specific heat capacity of Object 2 and four times the mass. If Object absorbs heat Q during this process, what is the amount of heat absorbed by Object 2? (A) (4/3)Q (C) 6Q (B) (3/4)Q (D) (/2)Q The transfer of energy from molecule to molecule is: (A) conduction (C) convection (B) equilibrium (D) radiation The process whereby heat flows by the mass movement of molecules from one place to another is known as: (A) inversion (C) convection (B) radiation (D) conduction Once a steady-state heat flow is established, the thickness of a wall built from solid uniform material is doubled. Relative to the original value, what is the result for the rate of heat loss for a given temperature difference across the wall?. 2. (A) / 2 (B) ¼ (C) 2 times (D) ½ If 60 g of material at 00 o C is mixed with 200 g of water at 0 o C, the final temperature is 40 o C. What is the specific heat of the material? (A) 2.2 kcal/kg. o C (C) 0.4 kcal/kg. o C (B) 6.3 kcal/kg. o C (D) 4.6 kcal/kg. o C An engineer is studying the rate of heat loss, Q/ t through a sheet of insulating material as a function of the thickness of the sheet. Assuming fixed temperatures on the two faces of the sheet and steady-state heat flow, which of the following graphs best represents the rate of heat transfer as a function of the thickness of the insulating sheet? 3. Compared to a giant iceberg, a hot cup of coffee has: (A) a higher temperature, but more thermal energy (B) a greater specific heat and more thermal energy (C) a higher temperature, but less thermal energy (D) more thermal energy and lower temperature 2

3 4. 5. An 830 g meteor impacts the Earth at a speed of,250 m/s. If its kinetic energy is entirely converted to heat of the meteorite, by what temperature does it increase? (Use specific heat for the meteor = 08 cal/kg. o C and cal = 4.86 J) (A),728 o C (C) 2,628 o C (B),346 o C (D) 7,42 o C A student heats 90 g of water using 50 W of power, with 00% efficiency. How long does it take to raise the temperature of the water from 0 o C to 30 o C? (Use specific heat of water c = 4.86 J/g o C) (A) 232 s (C) 59 s (B) 8 s (D) 5 s 6. A runner generates,260 W of thermal energy. If her heat is to be dissipated only by evaporation, how much water does she shed in 5 minutes of running? (Use the latent heat of vaporization of water Lv = 22.6 x 0 5 J/kg) (A) 500 g (C) 350 g (B) 35 g (D) 50 g An aluminum electric tea kettle with a mass of 500 g is heated with a 500 W heating coil. How many minutes are required to heat kg of water from 8 o C to 98 o C in the tea kettle? (Use specific heat of aluminum = 900 J/kg.K and specific heat of water = 4,86 J/kg.K) (A) 6 min (C) 8 min (B) 2 min (D) 4 min A 4.5 g lead BB moving at 46 m/s penetrates a wood block and comes to rest inside the block. If half of the kinetic energy is absorbed by the BB, what is the change in the temperature of the BB? (Use specific heat of lead = 28 K/kg.K) (A) 2.8 K (C).6 K (B) 3.6 K (D) 4. K When a solid melts, what change occurs in the substance? (A) Heat energy dissipates (C) Temperature increases (B) Heat energy enters (D) Temperature decreases Substance A has a higher specific heat than substance B. With all other factors equal, which substance requires more energy to be heated to the same temperature? (A) Substance A (B) Substance B (C) Both require the same amount of heat (D) Depends on the density of each substance What is the maximum temperature rise expected for a waterfall with a vertical drop of 30m? (Use acceleration due to gravity g = 9.8 m/s 2 and specific heat of water = 4,86 J/kg.K) (A) 0. o C (C) 0.5 o C (B) 0.06 o C (D) 0.07 o C The process whereby heat flows by means of molecular collisions is known as: (A) radiation (C) conduction (B) inversion (D) convection 3

4 A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper, with the aluminum and the copper in thermal contact. The specific heat capacity of aluminum is more than double that of coper. Which object experiences the greater temperature change during the time the system takes to reach thermal equilibrium? (A) Both experience the same magnitude of temperature change (B) The mass of each is required (C) The copper (D) The aluminum In liquid water of a given temperature, the water molecules are moving randomly with different speeds. Electrostatic forces of cohesion tend to hold them together. However, occasionally one molecule gains enough energy through multiple collisions to pull away from the others and escape from the liquid. Which of the following is an illustration of this phenomenon? (A) When a large steel suspension bridge is built, gaps are left between the girders (B) When John steps out of a swimming pool and stands in the wind, he feels colder than if he was not exposed to the wind (C) Increasing the atmospheric pressure over a liquid causes the boiling temperature to decrease (D) If snow begins to fall when Mary is skiing, she feels colder than before it started to snow Object has three times the specific heat capacity and four times the mass of Object 2. The same amount of heat is given to the two objects. If the temperature of Object changes by an amount of ΔT, what is the change in temperature of Object 2? (A) 2ΔT (C) ΔT (B) 3ΔT (D) (3/4)ΔT A machine part consists of 0.5 kg of iron and 0.20 kg of copper. How much heat must be added to the material to raise its temperature from 23 o C to 58 o C? (Use specific heat for iron = 470 J/kg.K and specific heat for copper = 390 J/kg.K) (A) 2,800 J (B) 5,98 J (C) 90 J (D) 4,200 J A glass window pane is 3. m high,.8 m wide and 9 mm thick. The temperature at the inner surface of the glass is 22 o C and at the outer surface 7 o C. Given the properties of glass listed below, how much heat is lost through the window every hour? Density 2,50 kg/m 3 Specific Heat 790 J/kg o C Coefficient of Linear Thermal Expansion 8. x 0-6 o C - Thermal Conductivity 0.8 W/m o C (A) 8.8 x 0 5 J (C) 2.7 x 0 7 J (B) 7.4 x 0 3 J (D) 4.3 x 0 4 J 28. An investigator uses 8 grams of water which is initially at 00 o C. The water is poured into a cavity in a very large block of ice initially at 0 o C. How many grams of ice melt before thermal equilibrium is attained? (Use the latent heat of fusion for ice Lf = 80 kcal/kg) (A) 80 g (C) 00 g (B) 0 g (D) 800 g 4

5 29. A sphere, 0.3 m in radius, has a surface emissivity of 0.55 and is at a temperature of 500 K. The sphere is surrounded by a concentric spherical shell whose inner surface has a radius of 0.8 m and emissivity of. The temperature of the shell is 400 K. What is the rate at which heat is radiated in the space between the sphere and the shell? (Use temperature of radiation TH in K, temperature of surrounding TC in K, Stefan Boltzmann constant x0 W / m K ) (A).3 kw (C) 3.6 kw (B) 4.3 kw (D) 7.8 kw A glass beaker of unknown mass contains 65 ml of water. The system absorbs,800 cal of heat and the temperature rises 20 o C. What is the mass of the beaker? (Use specific heat of glass = 0.8 cal/g. o C and specific heat of water = cal/g. o C) (A)342 g (C) 546 g (B) 39 g (D) 268 g The water flowing over a large dam drops a distance of 60 m. If all the gravitational potential energy is converted to thermal energy, by what temperature does the water rise? (Use acceleration due to gravity g = 0 m/s 2 and specific heat of water = 4,86 J/kg.K) (A) 0.34 o C (C) 0.09 o C (B) 0.44 o C (D) 0.4 o C SHOW ALL WORK FOR THE FOLLOWING CALCULATIONS IN THE FORMAT REQUIRED. Gold has a specific heat of 30 J/kg.0 C and a mass of.0 kg. If it absorbs 400 J of heat, how much will its temperature increase? 2. Water is poured into an insulated container from a height of 80 meters. How much does the temperature of the water increase? Specific heat of water is 486 kj/kg. 3. How much heat is required to raise the temperature of an empty 40-kg iron caldron from 0 0 C to 00 0 C? 4. If 400 cm 3 of water at 00 0 C is poured into a 300-g container initially at 20 0 C, what will be the final temperature T of the mixture when equilibrium is reached? Assume no heat flows into the surroundings. 5. A new alloy weighing kg is heated to C. It is quickly placed in 800 g of water at 0 0 C, which is contained in a 400-g aluminum calorimeter cup. The final temperature of the mixture is 40 0 C. What is the specific heat of the alloy? 5