Physics 110 Name________________________________________ Buoyancy, Heat & Temperature Quiz Formulas & Constants Q = m c ΔT 4.18 J = 1 calorie 1000 calories = 1 Calorie Cwater = 4190 J/kg oC Lfusion = 334,000 J/kg Lvaporization = 2,260,000 J/kg Cice = 205,000 J/kg oC Part I: Marbles are primarily composed of glass. In an experiment to determine the mass of a glass marble, a marble is placed in boiling water (100.0 oC) and allowed to reach thermal equilibrium. It is taken out and placed in 75.0 mL of room temperature water (20.0 oC). The temperature of the water increases to 25.5 oC. Show your calculations to determine the mass of the marble. Express your answer to 3 significant figures. Data Table

Water Marble

Mass Specific Heat Δ T Mass Specific Heat Δ T

0.0750 kg 4190 J/kg oC 5.5 oC 0.0273 kg 850 J/kg oC 74.5 oC

(0.0750 kg) (4190 J/kg oC) (5.5 oC) Mass of Marble = (850 J/kg oC) (74.5 oC) Benny’s had other glass marbles that were half the size (mass) of the marbles used in this experiment. If a smaller marble was used, what changes, if any, would occur in the following values? For the following criteria, circle the correct responses.

Change in temperature of the water Increased Decreased No Change

Specific heat capacity of the marble Increased Decreased No Change

Heat released by the marble Increased Decreased No Change

Benny’s had steel marbles that were the same mass as the marbles used in this experiment. Steel has a specific heat capacity of 450 J/kg oC. If a steel marble was used, what changes, if any, would occur in the following values? For the following criteria, circle the correct responses.

Change in temperature of the water Increased Decreased No Change

Heat released by the steel marble Increased Decreased No Change

Part II: I’m Melting! A piece of metal and a marble which have identical masses were placed in boiling water. They were removed and placed on the wax block and allowed to cool. Using your observations, compare the specific heat capacities for the marble and metal. The metal released more heat to the wax than the marble. Since the heat released is directly proportional to the specific heat capacity of the substance, the greater the heat released the greater the specific heat. The metal absorbed more heat energy from the boiling water and therefore released more heat to the wax upon cooling. Part III: Feel the Heat Place a finger as close as you can to the side of the flame. Then, place a finger as close as you can to the top of the flame. Where can you place a finger closer to the flame? Use the Kinetic Molecular Theory to explain your observations. You can place your fingers closer to the side of the flame because heat rises due to the fact that hot air is less dense than the cooler air surrounding the flame. Heat is transferred upward through the process of convection. As air is heated the particles increase their velocity and the spaces between particles increases causing an increase in volume and decrease in density. It is the more dense cooler air that is pushing the hot air upward. Place the nail into the flame for a short while until you feel the end of the nail becoming warm. Use the Kinetic Molecular Theory to explain your observations. Heat is transferred through the nail via conduction. The hotter and faster particles of the metal nail transfer energy to colder, slower particles through direct contact (collisions). Heat energy is transferred between particles so that hotter particles slow down (decrease velocity) while the cooler particles speed up (increase velocity).

Part V: Multiple Choice & Short Answer 1. A hot air balloon rises because a. hot air weighs less than cold air. b. hot air is composed of helium. c. hot air is less dense than cold air. d. hot air molecules push against the top of the balloon. e. air escaping from the bottom of the balloon pushes the balloon upward. 2. As a metal rod is heated at one end in a fire, the opposite end will become hot through the process of a. conduction b. convection c. radiation d. osmosis e. diffusion 3. Suppose you put a closed, sealed metal can of air on a hot stove burner. The contained air will undergo an increase in: a. density b. mass c. volume d. pressure e. weight 4. On a hot summers day I often sit in front of a fan to cool myself since I do not have air conditioning. The reason I feel cool is: a. The fan blows cool air across my skin. b. The air removes the heat from my skin. c. Perspiration condenses to remove the heat. d. The fan helps evaporate perspiration. 5. When you placed your hands on the upper flask of air on Galileo’s Thermoscope the temperature of the air increased and the water level in the glass tube: a. increased because of an increase in atmospheric pressure. b. increased because of a decrease in pressure inside the flask. c. decreased because of an increased in atmospheric pressure. d. decreased because of an increased pressure inside the flask. 6. When a bimetallic bar made of brass and iron strips is heated, the bar bends toward the brass strip. The reason for this is a. iron strip gets hotter before the brass strip. b. the brass strip gets hotter before the iron strip. c. the brass strip expands more than the iron strip. d. the iron strip expands more than the brass strip. 7. Wearing a black T-shirt on a hot summer day makes you feel hotter because: a. the color black reflects all of the light and absorbs the heat. b. the color black absorbs all of the light and reflects the heat. c. the color black absorbs all of the light and absorbs the heat. d. the color black absorbs all of the light which is converted to heat. 8. A refrigerator a. produces cold energy. b. causes thermal energy inside to disappear. c. removes thermal energy from the inside. d. converts heat energy into cold energy. 9. I crushed a soda can during a previous class. This was accomplished by a. increasing the pressure inside the can b. decreasing the pressure inside the can c. increasing the pressure outside the can d. decreasing the pressure outside the can