1 / 29

# Heat - PowerPoint PPT Presentation

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.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Heat' - walter-hebert

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Heat

The Fire Down Below

• 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”

• 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

• 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

• 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

• Fahrenheit to Celsius

Cº = 0.55 (Fº - 32º)

• Celsius to Fahrenheit

Fº = (1.8 x Cº) + 32º

• Celsius to Kelvin

K = C + 273

Adjusts for differences in Zero temperature

• Watts

• Newtons

• Joules

• Mishbohah

• From low E to high E

• From high E to low E

• Across layers of density

• Downwards, like gravity

• Heat

• Energy

• Potential Energy

• Temperature

The temperature scale used in the USA is substance’s…

• Fahrenheit

• Celsius

• Kelvin

• Thermocline

The temperature scale used in SI is substance’s…

• Fahrenheit

• Celsius

• Kelvin

• Thermocline

The temperature scale used in science is substance’s…

• Fahrenheit

• Celsius

• Kelvin

• Thermocline

Thermal Energy substance’s…

• 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 substance’s…

• 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 substance’s…

• Notice the cracks that have formed in the concrete after some time of thermal expansion

Conductors substance’s…

• 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 substance’s…

• 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 substance’s…

• Conduction

• HTB direct particle contact

• Convection

• HTB mass movement of particles

• Conduction

• Convection

What type of heat transfer describes why a dark shirt feels warmer on sunny days?

• Conduction

• Convection

What type of heat transfer describes how a A/C system changes room temperature?

• Conduction

• Convection

What type of heat transfer describes how lake water is hot on top and cold on bottom?

• Conduction

• Convection

• Conduction

• Convection

Specific Heat oven?

• 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 oven?

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 (Tfinal – Tinitial)

Homework 26 oven?

• Pg. 163 – Questions # 1- 4

• Pg. 170 – Questions # 1 - 4

• 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