Heat Transfer

Heat is responsible for changing matter from one phase to another Heat energizes the particles, adds temperature, and makes the atoms and molecules move faster

Heat Transfer Video on liquid nitrogen

Heat Transfer We measure heat in the unit known as calories A calorie is defined as the amount of heat to change 1 gram of water 1 C° We say “cal” for short calories is a kilocalorie

Heat Transfer Materials have a quantity known as specific heat capacity. Specific heat capacity is how much heat a material can hold per mass and degree Celsius. We use the variable “c” to define specific heat. Units are calories/(grams °C)

Heat Transfer The higher the specific heat capacity, the more heat a material can hold. Material with lower specific heat capacities get hotter quicker, like Iron or sand. Water has a high specific heat capacity = 1cal/g°C

Heat Transfer The quantity of heat, which will be defined with the variable Q, can be found with the following equation Q = mcΔT Heat = mass x specific heat capacity x Temperature change (Celsius)

Heat Transfer Try these problems

Heat Transfer You can calculate the heat required to change the phase of a material from one phase to another Q = mL Heat = mass x latent heat The units of latent heat are calories/gram. Every phase change has a specific latent heat. Heat of fusion involves interchanging between a solid and liquid, and heat of vaporization involves changing between a liquid and a gas.

Heat Transfer Example: The latent heat for water to vaporize to a gas from a liquid is 540 calories/gram. How much heat is needed to convert 1.2 kilograms of liquid water into a gas?

Heat Transfer Example 2: Calculate the heat released by 20 grams of 100°C steam that condenses and then cools to 0°C. The latent heat of vaporization for water is 540cal/g.

Heat Transfer Homework Pg 322: # 17, 20, 23 Pg 351: #2, 4, 8, 21, 22, 23