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Energy transfer by heating

3 methods - conduction, convection, radiation

the bigger the temperature difference between an object and its surrounding, the faster the rate at which energy is transferred by heating.

rate of transfer of energy depends on surface area and volume, object materials, surfaces.

Infrared Radiation

all objects emit and absorb infrared

the hotter an object is the more infrared radiation it emits in a given time

dark, matt surfaces are good aborbers and good emitters

light shiny surfaces are poor absorbers, poor emitters and good reflectors

Particles

In an object, the more kinetic energy the particles have, the hotter the object is.

Solid - fixed in place, least amount of KE but still some movement

liquid - some fixed arrangements, free to slide over each other, more KE than solids

gas - free to move about randomly, no fixed arrangement, lots of KE

Evaporation

Particles in a liquid are held together by forces

the particles need losts of kinetic energy to overcome these forces

particles can gain kinetic energy through heating but that energy has to come from somewhere

liquids on your skin get the energy they need for evaporation from your skin

so you skin is losing energy through heating the particles and it will feel coler

if particles are leaving the liquid on your skin through evaporation, they are taking kinetic energy with them

the average kinetic energy of the liquid on your skin has dropped