Thermal Energy Intro Video

Thermal Energy The total energy of particles of a substance or material. As thermal energy increases, particle movement increases. 3 states of matter: Solids – thermal energy is low due to little to no particle movement. Liquids – thermal energy is minimal due to slight particle movement. Gases – thermal energy is high due to rapid particle movement.

As thermal energy increases, particle movement increases.

Thermal Energy Reactions When a substance or material gains or loses thermal energy, two types of reactions are taking place: Endothermic Reaction – A chemical change that absorbs heat. Ice melting or water evaporating Exothermic Reaction – A chemical change that gives off heat. Digesting food, fire burning, or condensation.

Endothermic Reactions Energy is absorbed by a substance/material. The final temperature of the substance is greater than the beginning temperature. Potential energy < Kinetic Energy (Positive KE) +KE Activation Energy ΔH PE

Exothermic Reaction Energy is released by a substance/material. The final temperature of the substance is lower than the beginning temperature. Potential Energy > Kinetic Energy (negative KE) Activation Energy PE ΔH -KE

Heat A form of energy caused by the internal motion of molecules of matter. An increase in temperature = heat is being added. A decrease in temperature = heat is being removed. Measured in units called Calories. 1 calorie = the amount of heat needed to raise the temperature of 1g of water 1°C. The amount of heat needed for temperature change depends on the mass of the water being heated.

Specific Heat Capacity Mass is not the only factor that determines temperature change, what the substance is made of also affects its ability to absorb or lose heat – specific heat. The number of calories needed to raise or lower the temperature of 1g of a substance 1°C. Knowing the specific heat of a substance is useful in trying to decide what substance should be used for a specific purpose.

Specific Heats Mercury - .03 Water – 1.0 Copper - .09 What substance heats/cools the fastest? What substance heats/cools the slowest? To boil water the fastest, what type of pan would I want to heat it up in; aluminum, copper, glass or iron? Substance Specific Heat Air .25 Aluminum .22 Copper .09 Glass .2 Ice .5 Iron .11 Mercury .03 Ocean Water .93 Water 1.0 Wood .42 Mercury - .03 Water – 1.0 Copper - .09

Thermal Expansion As a substance gains or loses heat, the surface of the substance changes – thermal expansion. Gains heat = expands Molecules gain energy and therefore move more rapidly. Increases the substances volume and decreases its density. Loses heat = contracts Molecules lose energy and therefore move slower. Decrease the substances volume and increases its density.

Mechanics of a Hot Air Balloon Why does a hot air balloon fly? What needs to be done to get the balloon to land? Hot air = increased thermal temp. Increased volume Decreased density Balloon rises. Cooler air = decreased thermal temp. Decreased volume Increased density Balloon sinks

Heat Transfer 3 Types of Energy Transfer: Heat moves between objects constantly. But it always moves from a warmer object to a cooler object – Heat Transfer. 3 Types of Energy Transfer: Conduction Convection Radiation

Conduction The transfer of heat from one substance to another through direct contact. All molecules have motion: Faster = more heat energy Slower = less heat energy. Heat always moves from the faster moving particle (hot) to the slower moving particle (cold). Slower Faster

Conductor Vs. Insulator Any substance that permits the flow of heat or electricity freely – Conductor Any substance that does not permit the flow of heat or electricity freely – Insulator Example Insulator Conductor Using a metal spoon to stir hot water. Using a Styrofoam cup to carry hot coffee. Wearing a feather filled coat in the winter. Putting a paperclip into an electrical outlet. X X X X

Convection The transfer of heat by the movement of currents within a fluid (liquid or gas). Hotter fluid = faster moving particles less dense and rises to the surface. Cooler fluid = slower moving particles More dense and sinks to the bottom.

Convection Currents Many of nature’s occurrences happen due to convection currents. Wind Currents Continental Plates Shifting Ocean Currents

Radiation The transfer of heat energy through empty space by waves = electromagnetic spectrum. Does NOT require matter for the energy to be transferred. Low Energy High Energy 10-10 103 10-12 10-8 10-5