Forces, Motion, and Energy Ch. 6, Sec. 1 8th Grade - Mrs. Boguslaw Temperature Forces, Motion, and Energy Ch. 6, Sec. 1 8th Grade - Mrs. Boguslaw

What is temperature? a measure of the average kinetic energy of the particles in an object the faster an atom or molecule is moving, the more kinetic energy it has a measure of how hot (or cold) something is

What is temperature? temperature DOES NOT depend on how much of a substance you have

Particle Movement Particles of matter are ALWAYS moving …but in different directions …and at different speeds We can’t measure the kinetic energy of every particle, so we measure the average kinetic energy

Measuring Temperature Tool : thermometer How does it work? Thermal expansion thermal expansion: an increase in the size of a substance in response to an increase in the temperature of the substance as temperature increases, particles move faster and faster and spread out…which takes up more room!

Thermal Expansion at Work Expansion joints on highways Hot air balloons

Temperature scales

Temperature Scales Measured in… degrees Celsius degrees Fahrenheit Kelvins

Absolute Zero Absolute zero = 0 Kelvins The temperature at which atom movement STOPS Has not been achieved, but scientists have gotten close

Temperature Conversions

Forces, Motion, and Energy Ch. 6, Sec. 2 8th Grade - Mrs. Boguslaw What is Heat? Forces, Motion, and Energy Ch. 6, Sec. 2 8th Grade - Mrs. Boguslaw

Heat Heat: the energy transferred between objects that are at different temperatures Heat moves; cold doesn’t!

Thermal Energy thermal energy: the kinetic energy of a substance’s atoms

Conduction thermal conduction - the transfer of thermal energy from one substance to another through DIRECT CONTACT Example: when you put a hot spoon in a hot liquid, the end of the spoon eventually gets hot

Conductors and Insulators thermal conductor - a material through which energy can be transferred as heat thermal insulator - a material that reduces or prevents transfer of heat

fiberglass insulation Conductors Insulators curling iron flannel shirt cookie sheet oven mitt iron skillet plastic spatula copper pipe fiberglass insulation stove coil ceramic bowl

Convection convection - the transfer of thermal energy by the circulation or movement of a liquid or gas Example: boiling water repeatedly rises and sinks, wind is created by convection currents

Radiation radiation - the transfer of energy as electromagnetic waves Example: portable heater, the sun

Thermal Conductivity thermal conductivity - the rate at which a substance conducts thermal energy high thermal conductivity —> heat transfers easily low thermal conductivity —> heat doesn’t move through it easily

Specific Heat specific heat - the quantity of heat required to raise a unit mass of a homogenous material 1K or 1ºC conductors - low specific heats insulators - high specific heats Do you expect the specific heat of water to be low or high?

Calculating Heat heat = specific heat x mass x change in temperature heat = Joules (J) specific heat = J/kg x ºC mass = kg temperature = ºC

Forces, Motion, and Energy Ch. 6, Sec.3 8th Grade - Mrs. Boguslaw Matter and Heat Forces, Motion, and Energy Ch. 6, Sec.3 8th Grade - Mrs. Boguslaw

States of Matter states of matter - the physical forms in which a substance can exist three main states: solid, liquid, and gas

Solids particles do not move fast enough to overcome the strong attraction between them, so they are held tightly in place. particles vibrate in place

Liquids move fast enough to overcome some of the attraction between them particles slide past each other

Gases particles move fast enough to overcome almost all of the attraction between them particles move independently of each other

Changes in State changes in state - the change of a substance from one physical state to another only a physical change, not a chemical change. It looks different, but identity is the same

Forces, Motion, and Energy Ch. 6, Sec.4 8th Grade - Mrs. Boguslaw Heat Technology Forces, Motion, and Energy Ch. 6, Sec.4 8th Grade - Mrs. Boguslaw

Hot-Water Heating a hot-water heater raises the temperature of water water is pumped through pipes that go to a radiator in each room radiators heat the colder air around them water goes back to the water heater to be reheated

Warm-Air Heating air is heated in a furnace by burning fuel, usually natural gas Warm air travels to ducts in different rooms Warm air heats the rooms, cool air sinks down to a vent near the floor A fan forces cooler air back into the furnace to be heated

Heating and Insulation During cold weather, heat easily escapes a house; during warm weather, heat easily moves into a house Insulation reduces the transfer of thermal energy When insulation is used in walls, ceilings, and floors, less heat passes in and out of the building Keeps homes cooler in the summer (keeps hot air from moving in) and warmer in the winter (keeps hot air from moving out)

Solar Heating The sun gives off a LOT of energy Solar heating systems use the energy of the sun to heat homes and buildings can be passive (sun heats directly through the building) or active (see picture) Not great in really cold climates

Heat Engines heat engine: a machine that uses heat to do work heat engines burn fuel through a process called combustion external combustion engine: fuel burned outside the engine internal combustion engine: fuel burned inside the engine

External Combustion Engine

External Combustion Engines fuel is burned to heat water into steam Steam expands, which pushes a piston or a turbine The piston or turbine is attached to other parts of the machine that do work

Internal Combustion Engine

Internal Combustion Engines fuel (gasoline) is burned inside the cylinders in the engine Intake stroke - a mixture of gasoline and air enter the cylinders as the piston moves down Compression stroke - the crankshaft turns and pushes the piston up, compressing the fuel mixture Power stroke - a spark plug uses electrical energy to ignite the compressed fuel mixure As the fuel and air burns, it expands and forces the piston down Exhaust stroke - crankshaft turns and piston is forced back up, pushing exhaust gases out of the cylinder

Cooling Systems Cooling systems transfer thermal energy out of an area so that it feels cooler Thermal energy usually travels from higher temperature to lower temperature, so to move thermal energy the opposite way requires work Most cooling systems (like refrigerators or air conditioners) require electricity to do work

Thermal Pollution thermal pollution: the temperature increase of a body of water that is caused by human activity and has a harmful effect on water quality and the ability of that body of water to support life Often happens near large power plants If the temperature of water is increased, it can harm animals that live there and disrupt the ecosystem