Heat Chapter 9

Temperature 1. How hot or cold something feels 2. The amount of Kinetic energy a substance has a. Kinetic energy is energy of motion b. The more the molecules move, the more Kinetic energy they have. c. The more kinetic energy the molecules have the higher the temperature. d. The faster the molecules, the harder they hit and the further apart they spread out

Thermal Expansion 1. The higher the temperature the more the energy the molecules have 2. The more energy the molecules have the more they move 3. The molecules do 3 things a. Speed up b. Hit harder c. Move further apart

Thermal Expansion 4. When the molecules move further apart, the SUBSTANCE spreads out or EXPANDS 5. When the molecules slow down, hit less hard, and move closer together the SUBSTANCE gets smaller or CONTRACTS 6. Examples a. Potholes and side walk cracking

Measuring Temperature 1. Use a thermometer a. When the temperature of the liquid in the thermometer increases (move faster, hit harder, and move further apart), it expands up the tube. 1. The height of the tube depends on the temperature

Temperature Scales 1. Fahrenheit scale a. Freezing point 32 degrees b. Boiling point 212 degrees 2. Celsius Scale a. Freezing point 0 degrees b. Boiling point 100 degrees

Converting Fahrenheit and Celsius F to C: C = (5/9)(F-32) 86 degrees F into degrees C 86 degrees F into degrees C C = (5/9)(86-32) C = (5/9)(86-32) Order of operations states do parenthesis 1 st C = (5/9)(54) C = 5 x 54 / 9 Order of operations states multiply BEFORE divide C = 270 / 9 C = 30 degrees

Converting continued C to F F = (9/5)(C ) degrees C to degrees F = (9/5)(57 )+ 32 Order of operations says to multiply first F = (9 X 57)/ Order of operations says multiply before divide F = 513 / F = F = 134.2

Convert 10 degrees C into Fahrenheit F = (9/5)(C) + 32

Convert 45 degrees F into Celsius C = (5/9)(F - 32)

Thermal Energy 1. All of the potential (stored) energy, and the kinetic (moving) energy added together 2. The more molecules a substance has the more thermal energy it has 3. Example a. Which has more thermal energy a match or an ice sculpture? 1. Ice sculpture because it’s bigger (more molecules)

Heat 1. Definition: thermal energy that is transferred from one object to another 2. The amount of heat transferred depends on the difference in temperature between the two objects 3. Heat is transferred until both objects are the same temperature a. Heat moves from areas of high heat to areas of low heat

Conduction 1. Heat transfer by DIRECT touch (notice the “d” in conduction 2. Examples a. Curling or straightening hair with an iron b. Ironing your clothes c. Hot pizza and the roof of your mouth d. Holding an ice cube e. Touching something hot f. Frying food on the stove

Radiation 1. Definition: When heat is transferred through electromagnetic waves 2. Can transfer heat through a vacuum (like space) 3. Examples a. We get heat from the sun by radiation b. Holding your hands over a fire to “feel the heat”

Convection 1. Definition: Heat transfer through fluids (liquid or gas) 2. Examples: a. Blow drying your hair b. Boiling noodles c. Water cycle d. A fan blowing hot air e. Baking food in the oven

Water Cycle (natural convection) 3. The cold temperature causes the molecules to slow down, hit less hard and move closer together. Density increases and move closer together. Density increases Water vapor turns back into water (condenses) 2. Water vapor rises through the 4. water falls as rain Atmosphere to the top where its cold 1. Puddle on the ground Sun heats up the water (the molecules speed up, hit harder, and move further apart density decreases) Water turns into a gas (evaporates)

Forced Convection 1. When an outside force pushes a fluid 2. Examples a. Computer fan b. Ceiling fan c. Oscillating fan

Thermal Conductors 1. Definition: a materials that easily transfers heat a. Usually metal (because of metallic bonds) 1. Metal atoms share e-, so there’s already a path for the heat to follow b. Glass

Thermal Insulators 1. Definition: Materials that do NOT allow heat to transfer a. The atoms hold on to their e- tightly b. Examples 1. Air 2. Plastic 3. Cloth 4. Wood 5. 5.

Specific Heat 1. The amount of heat needed to raise the temperature of 1 kg of that substance by 1 degree. a. A substance with a low specific heat, heats up quickly, and cools off quickly 1. Like sand on the beach. It’s very hot at 12:00pm, but by 3:00 it’s cool b. A substance with a high specific heat, heats up slowly, and cools of slowly 1. Like a pool full of water. Its fun to go night swimming because the water stays warm from the day

Thermal Pollution 1. Increasing the temperature of a body of water a. The warmer water has less oxygen in it 1. Organisms die due to lack of oxygen b. The warmer water makes organisms more sensitive to chemical pollutants, parasite and diseases.

Heat Engine 1. Converts (changes) thermal energy into mechanical energy 2. Forms of energy a. Chemical energy 1. Energy stored in the chemical bonds of substances b. Mechanical energy 1. Energy from machines c. Nuclear energy 1. Energy stored in the nuclei of an atom d. Radiant Energy 1. Energy from electromagnetic waves

The Law of Conservation of Energy 1. Energy can not be created or destroyed, it just changes forms a. All the energy that was here when the dinosaurs were here, is still here a. All the energy that was here when the dinosaurs were here, is still here b. It’s just in different forms

Internal Combustion Engines 1. Fuel burns in a combustion chamber in the engine a. Gas is release at the top of the cylinder, right above the piston. b. The spark plug “sparks” setting the gas vapor on fire, causing a small explosion c. The small explosion forces the piston downward. d. The piston then pops back up e. The up and down motion of the piston turns a “crankshaft”, which in turn, turns the wheels

Refrigerators/air conditioners/ heat pumps 1. Work by removing heat from objects by using a liquid coolant 2. The liquid coolant is forced through an expansion valve, and changes into a gas 3. The gas is VERY cold. Heat from the objects in the refrigerator moves from the objects to the cold gas.

Releasing Thermal Heat 4. The gas is still colder than the outside air (so the heat won’t move) 5. The coolant goes through a “compressor” that pushes all the gas together. This warms the gas up 6. The heat from the gas is now warmer than the room, so it will be blown out the bottom of the fridge into the room