Name: _ Period: Date: _ Notes: Thermal Energy Transfers Directions: Read/complete the following sections on the Transfer of Thermal Energy Conduction Heat is transmitted by conduction, convection and radiation. CONDUCTION is the movement of heat from something hot to something colder, by direct contact, but without perceptible movement of the substances themselves. The amount of heat transferred is proportional to the difference in temperature between the two bodies, the contact surface area and the material they are made of. The effectiveness of any substance in conducting heat is called its thermal conductivity. Metals are good conductors; glass, plastic and ceramics are poor conductors, which can protect us from heat. In practical terms this means that a metal saucepan will heat a sauce quickly, but it needs a plastic handle to make it possible for us to touch it. Liquids and gases are fluids, which expand when they are heated. The particles in these fluids can move from place to place very quickly when hot. Conductor- Thermal energy flows freely through an object Insulator- Thermal energy does not flow freely through an object Convection CONVECTION occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection. A practical example is heating water or oil in a pan to cook food. Radiation RADIATION is heat carried by electromagnetic waves (infrared rays) from a hot body and absorbed by a colder body. The transmission by radiation takes place with no direct contact between the bodies and it is only possible provided that there is nothing between them that can absorb the waves. In other words heat radiation mainly takes place in a void or in the air. For all cooking methods, apart from heat radiation, you need both a source of heat and a conductor. Conductors can be animal or vegetable fats, water or water vapour, air, metal, ceramic or pots and pans made of other materials. Label the following pictures with the correct term (Conduction, Convection, Radiation)
Answer the following statements with the correct term (Conduction, Convection, Radiation)
1. Hot coffee is stirred with a spoon, the spoon gets hot due to 2. A chair is placed several feet from a fire in a fireplace. The fireplace has a glass screen. The side of the chair facing the fireplace gets warm because of 3. A certain type of decorative lamp contains colored liquids. These liquids form globs that break off and rise to the top of the liquid. The globs rise due to 4. Near the ceiling of a room the air is warmer. The warm air rises because of 5. A college student holds the back of his hand near an iron to see if it is hot. Heat is transferred to his hand by 6. A heater is placed under one corner of a water bed mattress. Warm water moves throughout the mattress because of 7. A certain type of stainless steel cookware has a layer of copper applied to the bottom to help it heat evenly. The copper transfers heat to the pan by 8. In a swimming pool, the water near the surface is slightly warmer. The warm water rises because of 9. One end of a copper rod is placed in a flame of a Bunsen burner. Small pieces of wax placed along the rod melt at progressively larger distance from the flame. Heat is transferred through the rod by 10. A house burns down. On the house across the street, all of the vinyl siding is twisted and warped by the heat. The heat was transferred across the street by 11. Warm air over the beach rises while cooler dense air from the ocean rushes in due to 12. The metal skewer gets so hot that you drop your marshmallow in the campfire because of 13. A huge rock at the state park gets so hot during the day that you can t sit on it from 14. You lay on that same rock at night so that you can keep warm by 15. A fireman feels a door and it is hot from the fire on the other side due to 16. The cause of weather systems on earth is 17.You are in the top bunk of a bunk bed and you want to turn the air conditioner on while your friend on the bottom bunk is fine is caused by
Look at the graph showing the conductivity of different materials and write a short paragraph describing it. Use the information from the text to help you and remember to include the following information: A general description of the graph (include the terms insulators and conductors) Which materials we use to heat things in the kitchen (i.e. good conductors); Which materials we use to protect ourselves from heat (i.e. for handles, spoons, etc.); Which materials we use to eat and drink out of (i.e. cups, plates, dishes), keeping food warm but not impossible for us to touch Which materials we use to eat with (cutlery).