Heat and Heat Transfer

EQ: How can Thermal Energy (heat) be transferred from one object to another?

Forms of Energy Mechanical Electrical Electromagnetic Nuclear Chemical Sound Thermal

HEAT (Thermal Energy) Created by the movement of particles (atoms) that produces heat. Energy can take on many forms and can change from one form to another. Many different types of energy can be converted into heat energy. Light, electrical, mechanical, chemical, nuclear, sound and thermal energy itself can each cause a substance to heat up by increasing the speed of its molecules. put energy into a system and it heats up, take energy away and it cools.

Heat (Thermal Energy) The more energy that goes into a system, the more active its molecules are. The faster molecules move, the more heat or thermal energy they create. The amount of heat a substance has is determined by how fast its molecules are moving, which in turn depends on how much energy is put into it.

Heat Heat (thermal energy) is transferred from one object to another when the objects are at different temperatures. Thermal Energy always moves from a warmer object to a cooler object

Thermal Energy moves through matter in 3 ways: Conduction Convection How does heat move? Thermal Energy moves through matter in 3 ways: Conduction Convection Radiation

Conduction The transfer of heat by direct contact (particles collide) “the process that moves energy from one object to another when they are touching physically” The transfer of heat by direct contact (particles collide) Physical contact must be made for conduction to occur

Conduction Occurs most easily in solids and liquids In order for conduction to occur, objects must be at different temperatures and must come into contact with each other Occurs most easily in solids and liquids

Conductors Conductor - “substances that transfer thermal energy very well” Conductors have a low specific heat in most cases Example: copper, gold, and iron

Insulators Insulator- “substances that do not transfer heat very well” Electrons move extremely slow through good insulators Electrons are tightly bound to the atoms in good insulators and electrons are not free to move around Good Insulators: wood, plastic, foam, rubber, glass

Convection “ the flow of currents in a liquid or gas” The process that transfers energy by the movement of large numbers of particles in the same direction within a liquid or gas. Kinetic energy increases, particles spread out over a large area. “ the flow of currents in a liquid or gas” A current is created when the warmer (less dense) material rises forcing the cooler (more dense) material to sink

How does convection happen?? Kinetic energy increases -> particles spread out Increased distance between particles -> decrease in the density Cooler, denser mass of the gas of liquid replaces a warmer, less dense mass of the gas or liquid by pushing it up Convection is a cycle in nature responsible for most winds and ocean currents.

How does convection happen??

How does convection happen??

How does convection happen??

Convection Hot air rises in the atmosphere as cool air sinks EXAMPLES OF CONVECTION: Hot air rises in the atmosphere as cool air sinks Hot water rises to the top (rolling boil) as cold moves to the bottom of the pot to be heated up and sent to the top of the water again. In a fire, you are always told to get on all fours and crawl across the floor because the warm air (smoke filled) will rise and cool air (non-smoke air) will sink to the bottom. A basement in a house is known for being naturally cooler than an attic (which is known for being hot/warm) because of convection.

Radiation “Heat transfer through space by electromagnetic waves (light)” Visible light Microwaves Infrared light The Sun is the most significant source of radiation on Earth ALL OBJECTS emit SOME radiation ALL OBJECTS absorb radiation Can travel through empty space, occurs in solids, liquids, and gasses. Moves from warmer to cooler objects

Examples of Radiation Waves such as visible light, infrared, and ultraviolet light Heat from a light bulb Microwave oven You get a sunburn from being in the sun too long Cooking a hamburger over a charcoal flame

Radiation

Radiation https://www.youtube.com/watch?v=5GoZZKcNZiQ