 What Is Heat

Objectives:

1.    Define how heat is defined in the kinetic theory.

Key Terms:

kinetic theory

Notes: (12-5)

Temperature and Heat:

When you ask most people what heat is you will see that there is little understanding of if except that it is hot.  Some may tell you that it is a form of energy but exactly what form is it and how is it created?  Early scientists (Antoine Lavoisier) thought that heat was an invisible weightless fluid that flowed from one substance to another.  Lavoisier called this substance caloric (now called the calorie).  Over time this theory lost favor with the scientific community and the Kinetic Theory became excepted as the explanation of heat. Heat is due to the motion and vibration of particles in matter Temperature is the measure of the kinetic energy of molecules Heat transfer is the transfer of kinetic energy from one substance to another (hotter to colder)

Heat is the amount of kinetic energy in a substance – depends on the mass Can measure temperature not heat Unit is the calorie (cal) or joule (J) 1cal = 4.184J a cal is the amount of heat needed to raise 1g of water 1 degree

Specific heat Is the amount of heat (cal) needed to raise 1g of a substance 1oC Can be used to calculate the amount of heat gained or lost by a substance Is the ability of a substance to absorb heat High specific heat – slow to heat up and slow to cool down (& visa versa)

Calculating heat energy Can be measured using a calorimeter Mass · DT · Specific heat
Heat PE can be stored in the bonds of fuels and food