Energy 7a. Designing a diagram, model or analogy to show or describe the motion of molecules for a material in a warmer and cooler state. 7b. Explaining the difference among conduction, convection, and radiation and creating a diagram how heat energy travels in different directions and through different materials by each of these methods.

Vocabulary Combustion-chemical change that gives off heat and light. Conduction-energy transfer by contact between particles. Convection-energy transfer by the movement of a large mass of liquid or gas. Expansion-an increase in the size of an object. Heat-amount of energy transferred from one object or place to another

Specific Heat-A material’s ability to take in or give off heat. Insulator-Object or material that prevents conduction. Kinetic Energy-The particles of matter are in constant motion. Radiation-Transfer of energy as waves. Temperature-measure of the average kinetic energy of matter.

Temperature Temperature is a measure of the average kinetic energy of the individual particles in an object. Kinetic Energy is energy of motion.

Temperature Scales Fahrenheit Scale Celsius Scale Kelvin Scale

Thermal Energy Thermal Energy is the total energy in a substance. Depends on The temperature The mass How the particles are arranged.

Specific Heat Different Materials heat up and cool down at different rates. The amount of energy required to raise the temperature of 1 kilogram by 1 degree Kelvin Water has a high specific heat. It takes in and gives off heat very slowly.

Specific Heat Examples A lake’s large mass and water’s high specific heat prevent the lake’s temperature from changing quickly. Iron and Aluminum have low specific heats. Because they heat up quickly, they make good cooking utensils.

Producing Heat A heat source is anything that gives off heat. Most forms of energy produce heat. Heat moves from regions of high temperature to regions of low temperature.

Forms of Energy that Produce Heat 1. Electrical Energy- A. Toasters B. Irons C. Light Bulbs

2. Chemical Energy-Combustion of wood, oil, gas.

3. Mechanical Energy-Friction (two objects in motion that are in contact).

3 Types of Heat Transfer Conduction Convection Radiation

Conduction Objects are in direct contact. (Solid) The hot object transfers heat to the cold object. The fast moving particles in the hot object bump into the particles in the cold object and make them move faster.

Conductor Examples Metals such as aluminum and copper are good conductors of heat. Cloth, wood, and plastic are not good conductors. Poor conductors are insulators.

Convection Mass of liquid or gas moves. The material flow is a convection current. Most air and water currents are convection currents. A temperature difference between two places causes a convection current.

Convection Current Example: Heating a room in winter Air is heated by the radiator. Hot air is less dense than cold air and rises. As the hot air mixes with cool air it cools and falls. The cooler air sinks to the floor and is pushed toward the radiator for reheating by a current of air.

Other Convection Examples: Earth’s Tectonic Plates Atmospheric Currents Lake Turnover

2. Air Currents

3. Lake Turnover

Radiation Transfer of energy through waves.

Radiation Materials with dark colors absorb more radiant heat. Light colors reflect radiant energy. Air and glass allow radiation to pass through.

Radiation Example On a cold winter day, the sun shines through a window and warms you. The outside air and the window remain cold because the radiant energy pass through them without warming them.

Thermos A vacuum is an empty With no molecules to Transfer heat through Conduction or Convection. The shiny interior and exterior Prevents radiation energy from Entering from the outside or leaving From the Inside.

Expansion and Contraction Almost all materials take up more space when heated and less space when cooled. The Golden Gate Bridge is 1.5 meters longer during the summer than it is during the winter.

Water Cooled water contracts until it reaches 4 degrees Celsius. Below this temperature, water expands until it freezes at 0 degrees C.

Water The expansion makes ice less dense than water. So ice floats in water.