Heat The Fire Down Below

Heat A flow of energy from objects of higher thermal energy to objects of lower thermal energy Heat is measured in Joules (J) because it is a form of energy Described as a flow from hot to cold No such thing as “cold”

Temperature Based on the motion of the particles in a substance Fast motion = high temperature Slower motion = lower temperature Relatively describes how the particles collide with the surface of the thermometer Collisions transfer energy

Temperature Scales Fahrenheit Common in the US Freezing point of water is 32ºF Boiling point of water is 212ºF Celsius Common in the rest of the world (SI) Freezing point of water is 0ºC Boiling point of water is 100ºC

Temperature Scales Kelvin Used for science, as there are NO negative values 0K is set at Absolute Zero, the temperature at which all particle motion stops Freezing point of water is 273K Boiling point of water is 373K NOTE – 100K between freezing and boiling, so Kelvin uses the same degrees as Celsius

Converting Temperatures Fahrenheit to Celsius Cº = 0.55 (Fº - 32º) Celsius to Fahrenheit Fº = (1.8 x Cº) + 32º Celsius to Kelvin K = C Adjusts for differences in Zero temperature

Because heat is a form of energy, heat is measured in … 1.Watts 2.Newtons 3.Joules 4.Mishbohah

Heat always flows… 1.From low E to high E 2.From high E to low E 3.Across layers of density 4.Downwards, like gravity

The average motion of particles in a substance defines that substance’s… 1.Heat 2.Energy 3.Potential Energy 4.Temperature

The temperature scale used in the USA is 1.Fahrenheit 2.Celsius 3.Kelvin 4.Thermocline

The temperature scale used in SI is 1.Fahrenheit 2.Celsius 3.Kelvin 4.Thermocline

The temperature scale used in science is 1.Fahrenheit 2.Celsius 3.Kelvin 4.Thermocline

Thermal Energy Usually based on the total number of particles, as most temperatures in which we survive are relatively close together (-15ºF to 130ºF) More particles = more thermal energy Ex. boiling cabbage, frying foods, ocean water

Thermal Expansion As substances increase in temperature, the particles move apart Substances expand and become less dense when heated Substances shrink and become more dense when cooled Explains expansion joints in bridges and concrete sidewalks Water is one very important exception

Examples of Thermal Expansion Notice the cracks that have formed in the concrete after some time of thermal expansion

Conductors Allows heat (and electricity) to flow easily with little or no resistance Heats up quickly, cools down quickly Low “Specific Heat” Usually metals High density, free electrons

Insulators Resist the flow of heat (and electricity) High “Specific Heat” Resisted heat can build up and cause the substance to burn Usually nonmetals Large molecules, no free electrons

Heat Transfer Conduction HTB direct particle contact Convection HTB mass movement of particles Radiation HTB invisible infrared radiation

What type of heat transfer describes cooking on an electric range? 1.Conduction 2.Convection 3.Radiation

What type of heat transfer describes why a dark shirt feels warmer on sunny days? 1.Conduction 2.Convection 3.Radiation

What type of heat transfer describes how a A/C system changes room temperature? 1.Conduction 2.Convection 3.Radiation

What type of heat transfer describes how lake water is hot on top and cold on bottom? 1.Conduction 2.Convection 3.Radiation

What type of heat transfer describes cooking in an electric oven? 1.Conduction 2.Convection 3.Radiation

Specific Heat Amount of energy that has to be lost or gained by a substance to change temperature Note: Water has an incredibly high specific heat value due to the bonds between water molecules

Specific Heat Q = m c  T where m is the mass of the substance c is the specific heat value  T is the change in temperature of the substance (T final – T initial )

Homework 26 Pg. 163 – Questions # 1- 4 Pg. 170 – Questions # 1 - 4

Layers and Heat Transfer Layers trap air in a “dead air space” More layers mean it’s harder to change temperatures between layers Ex. double-paned windows, dressing in layers, layers of construction on a house

More on Radiation Emitters are substances that give off radiation Stars, campfires, space heaters, etc. Absorbers capture radiation Black shirts, asphalt, water Reflectors return most of the radiation that is emitted towards them Mirrors, aluminum foil, ice & snow