SWYK Unit 4 Thermal Energy

You have two liquids at 20°C. You heat each to 21°C. It takes more heat to get liquid B from 20°C to 21°C than it does liquid A. What can you tell about the two liquids, now at 21°C?

• Liquid A has more kinetic energy than liquid B.
• Liquid B has more kinetic energy than liquid A.
• Liquid A has more thermal energy than liquid B.
• Liquid B has more thermal energy than liquid A.

What event does this diagram of a collision between particles illustrate?

• the transfer of thermal energy through conduction, where the top substance is cooler than the lower substance
• thermal equilibrium, where the top substance is cooler than the lower substance
• thermal equilibrium, where the top substance is hotter than the lower substance
• the transfer of thermal energy through conduction, where the top substance is hotter than the lower substance

You fill two ice pop molds from the same room-temperature pitcher of lemonade. You put both in the freezer at the same time. After an hour, you take both out. One is frozen solid and one is only partially frozen. What can you infer?

• The mass of the frozen ice pop is less than the mass of the partially frozen ice pop.
• The type of matter of the frozen ice pop is less than the mass of the solidly frozen ice pop.
• The thermal energy of the frozen ice pop is greater than the thermal energy of the partially frozen ice pop.
• The kinetic energy of the frozen ice pop is greater than the kinetic energy of the partially frozen ice pop.

Different metals conduct heat at different rates. The table below ranks the thermal conductivity of five common metals. Which metal would you choose to line the bottom of your cooking pot for a faster rate of heating water and why?

• Bronze because it has a low thermal conductivity.
• Brass because it has a middle thermal conductivity.
• Copper because it has a high thermal conductivity.
• Any of the metals would be good since they all conduct thermal energy.

You decide to take a bath and discover that the water in the tub is different temperatures in different places Before getting into the tub, what type of thermal energy transfer could you use to get the water to thermal equilibrium.

• Thermal equilibrium can't be reached.
• Conduction
• Convection
• Raditation

The table below shows the thermal conductivity of four substances. Which substances should you use to spread heat quickly and which ones should you use to protect something against heat?

• for both spreading heat and protecting against heat, gold and aluminum
• for spreading heat, gold and aluminum; for protecting against heat, snow and Teflon
• for spreading heat, aluminum and snow; for protecting against heat, Teflon and gold
• for spreading heat, snow and Teflon; for protecting against heat, gold and aluminum

You have a sunroom. However, you are unable to enjoy it most of the time because it gets very hot during the day when the sun shines and very cold at night after the sun sets. You want to cover the room by using a material that can absorb heat during the day and then give off heat at night. What kind of material are you looking for?

• a material with low heat capacity
• a material with high heat capacity
• a material with low heat capacity and low conductivity
• a material with high heat capacity and high conductivity

Jorge wants to build a bench to use next to a swimming pond near his house. He has bricks, wood and plastic available to him. Since the bench will be in the sun and he will sit on it after swimming, Jorge is mostly concerned that the material might get too hot. What can Jorge do to make sure he builds a bench that is a comfortable temperature to sit on AND takes the least amount of work to build?

• Before building the benches, Jorge can touch each material to see whether it feels cool or warm to the touch. If he likes the feel of brick or wood, he can use that material. Otherwise, he should ask his mother to bring home the plastic blocks.
• The most efficient method is to build two benches, one each of wood and brick, and test them one sunny day in July. If Jorge is not satisfied with the temperature of the bench when he sits on it, he can ask his mother to bring home the plastic blocks to make a third bench.
• Jorge can research the density of all three materials online. He can leave the wood and bricks in the sun for a day in summer and touch them to determine if they are too hot or cool, then compare their density to that of the plastic blocks to determine which material he should use.
• Jorge can research the thermal conductivities of all three materials online. He can leave the wood and bricks in the sun for a day in summer and touch them to determine if they are too hot or cool, and then compare their conductivities to that of the plastic blocks to determine which material he should use.

Three identical flasks of boiling water were put into three identical wooden boxes. The first box has just air in it, the second box was filled with Styrofoam, and the third was filled with sand. The temperatures were recorded at one-hour intervals. The results are shown. Which material is the better insulator?

• Air
• Styrofoam
• Sand

Dew occurs when water vapor changes to liquid water on surfaces that have cooled during the night. What is happening to the thermal energy as the water changes from water vapor to liquid water?

• Thermal energy decreases as water turns from vapor to liquid.
• Thermal energy increases as water turns from vapor to liquid.
• Thermal energy becomes equal as water turns from vapor to liquid.
• There is no change in thermal energy as water changes from vapor to liquid.