Thermal energy Chapter 4

Energy-influences everything.

Energy-The ability to cause change. Change in position or motion.

Kinetic Energy-Energy due to Motion. Kinetic energy has momentum. Momentum-the quantity of motion that an object has.

Kinetic Energy The faster the object moves, the more kinetic energy it has.

Kinetic Energy Depends on mass and speed.

Potential Energy-stored energy due to the interaction between objects and particles(position).

Potential Energy Objects with potential energy have the possibility to cause change.

Mechanical Energy-The sum of the potential and kinetic energy in a system.

Thermal Energy-the sum of kinetic and potential energy in particles of matter due to their random motion.

Thermal Energy

Temperature-The average kinetic energy of the particles that make up a material.

Temperature Two materials can have the same temperature but different thermal energy. Ex.-Ice/Water

Temperature

Thermometer-an instrument used to measure temperature.

Thermometer A bulb thermometer uses expansion and contraction of a liquid to measure temperature.

Thermometer An electronic thermometer measures the resistance in a circuit to measure temperature.

Temperature-the measure of the average kinetic energy of the particles in a material. Units-Kelvin (K)/Celsius(C)/Fahrenheit(F)

Low Kinetic Energy=“cold” Absolute Zero= –459.67F/–273.15°C Absolute zero-the lowest theoretically possible temperature. Atoms stop all movement.

Transfer of Thermal Energy *Heat-The movement of thermal energy from a region of higher temperature to a region of lower temperature. –Heating only occurs when thermal energy is transferred from one object to another.

Thermal Pollution-Adding warmer substances that increase the temperature of another substance. Increasing water temperature by adding warmer water.

Heat Transfer-the rate of transfer depends on the difference in temperature. The greater the difference in temperature, the faster the transfer. Heating continues until all substances that are in contact have reached the same temperature.

Heat Transfer Conduction-the transfer of thermal energy due to collisions between particles.

Thermal Conductor-material in which thermal energy moves quickly (metals).

Insulator-material in which thermal energy moves slowly(nonmetals).

Insulator An insulated can decreases the amount of heat flow, keeping it cold.

Conductors-low specific heat Insulators-high specific heat Specific Heat-the amount of thermal energy it takes to increase the temperature 1kg of a material by 1 degree Celsius. Conductors-low specific heat Insulators-high specific heat Water-high specific heat-good for cooling.

Thermal Expansion-the increase in volume that a material undergoes when the temperature increases. At higher temperatures, the particles are moving faster, requiring more space.

Thermal Contraction-the decrease in material’s volume when it’s temperature decreases.

Heat Transfer Convection-the transfer of thermal energy by movement of the particles from part to another. Occurs in fluids and gases.

Convection

Forced Convection

Heat Transfer Radiation-the transfer of thermal energy by electromagnetic waves. Energy transfer in a vacuum. All objects emit some form of electromagnetic radiation.

Radiation

Changes of State Melting/Freezing-Adding or taking away thermal energy.

Changes of State Vaporization/Condensation

Changes of State Sublimation/Deposition

Energy Transformation

The Law of Conservation of Energy. Energy cannot be created or destroyed. It can only change forms or move from one region to another.

Heating Appliances-devices that convert electric energy in to thermal energy.

Thermostat-a device that regulates temperature.

Refrigerator/Air conditioner-a device that uses electrical energy to pump thermal energy from a cooler location to a warmer location.

Refrigerator process A coolant flows through a pipe. It pulls thermal energy from the inside of the refrigerator and takes it out of the chamber. Good refrigerants have a low boiling point.

Heat Pump-a device that can be used for cooling and heating.

Heat Engine-a machine that converts thermal energy to mechanical energy. Combustion takes place outside the engine.

Internal Combustion Engine

Internal Combustion The fuel burns in a combustion cylinder chamber.

Combustion Diesel fuel is ignited by compression. Gasoline Fuel is ignited by a spark.

Cylinders-The more you have the more powerful the engine.