Week 1 Heat energy and transfer

heat

form of energy; energy that flows from higher temperature object to a lower temperature object

how is heat measured in SI unit?

in Joules (J) [because SI unit for energy is joules]

temperature

the degree of hotness or coldness of a substance

what is temperature measuring?

measures the heat energy (which is related to the average kinetic energy) of the particles in a sample of matter

the three temperature scales

celsius, fahrenheit, and kelvin scale

formula to convert celsius to fahrenheit

(C x 1.8) + 32 = F

formula to convert fahrenheit to celsius

(F - 32) x 5/9 = C

formula to convert celsius to kelvin

C + 273.15 = K

formula to convert kelvin to celsius

K - 273.15 = C

types of temperature measuring devices

liquid in glass thermometer, thermocouple, resistance temperature detectors, thermistors, temperature indicators - thermochronic paints, temperature indicating crayons

the three modes of heat transfer

conduction, convection, radiation

conduction

transfer of energy (in the form of heat) from one part of a body to another (or from one body to another) without the particles of the body being exchanged

what does conduction require?

contact

what is conduction associated with?

solids (can take place in liquids and gases but not as effective because the atoms or molecules are more spread apart [harder to collide with each other])

where can there not be any conduction of heat?

in vacuum

convection

process in which heat is carried form one place ot another by the bulk movement of a fluid (i.e. gas or liquid)

can there be convection of heat in a solid?

no (solid will conduct heat not convect)

where can there not be any convection of heat?

in vacuum and solids

radiation

transfer of heat energy from a hot body to a cooler one by electromagnetic waves

does radiation require matter to transfer thermal energy?

no (meaning heat transfer by radiation can take place in a vacuum)

vacuum

a space that contains very little or no matter, creating a region of extremely low pressure (ex. outer space)

what is the mechanism for conduction?

the atoms or molecules with more heat (more kinetic energy) move faster and bump into other atoms or molecules, causing them to move faster, which also means they gain more heat energy

(for metals, the same happens but their free electrons spread throughout the metal, transporting the energy much quicker, making them great conductors)

as fluid gets heated it moves faster, which leads to 

its density decreasing as the atoms or molecules spread out

what happens when the fluid becomes less dense

it rises

convection current

fluid gets heated, gains energy, becomes less dense, and rises —> cooler fluid replaces the heated fluid, then it also gains energy, and rises, and the cyle repeats

do all “hot” (above absolute zero) objects emit heat radiation?

only if it’s hotter than its surroundings

what object surface is the best at emitting/absorbing heat radiation?

matte black

what object surface is the worst at emitting/absorbing heat radiation?

shiny silver (it relfects the radiation)