Energy and Specific Heat Date:

Energy The ability to do work Multiple forms of energy We are going to focus on heat, q

Chemical Potential Energy Energy stored in the composition of the chemical – how the atoms are bonded.

Law of Conservation of Energy Just as matter is conserved, energy is too Energy cannot be created or destroyed by any physical or chemical change, it is simply transferred.

Thermochemistry Thermos (Greek) hot Heat changes that occur with chemical reactions

Burning Calories During exercise bodies break down sugar and/or fat to CO 2 and H 2 O and produce heat A Calorie (notice the big C) is actually a kilocalorie

A calorie The amount of energy/heat to raise temperature of 1 g H 2 O 1 o C. So a 2000 Calorie diet is actually a calorie diet The SI Unit of heat is the Joule –1 cal = J

Heat Capacity The amount of heat to change an objects temperature by 1 o C Depends on mass and composition –Soup or toast to warm you up?

Specific Heat The amount of heat necessary to raise the temperature of one gram of a substance one degree Celsius. (Water’s specific heat is one cal). J/g o C cal/g o C

High specific heat –Takes a lot of heat to change the temperature therefore heats up and cools down SLOWLY –Glass pan Low specific heat –Takes less heat to change the temperature therefore heats up and cools down QUICKER –Al foil

Beach set up

How do we calculate energy? Energy = mass * specific heat * temperature change q = m*s*  T  T = T f – T i

Since J of heat were used to raise the temperature of 160 g of wood to 150 o C, what was the original temperature of the wood? Specific heat of wood 1.8 J/g o C.

If -180 J of heat were released when the temperature of grain alcohol was lowered by 5 o C, how many grams of grain alcohol were present? (2 SF) Specific heat of grain alcohol 2.4 J/g o C.

How much heat in calories is necessary to raise the temperature of 163 g of silver 106 o C? Specific heat of silver 0.24 J/g o C (3 SF)

If 960 J of heat are added to 10 g of chloroform, what is the temperature change that will result? Specific heat of chloroform 0.96 J/g o C

If 1920 J of heat are used to heat 200g of silver to a temperature of 75 o C, what was the initial temperature of the silver? Specific heat of silver 0.24 J/g o C

If 4232 J of heat is used to heat 230 g of iron originally at 13 o C, what is the final temperature of the iron? Specific heat of iron 0.46 J/g o C

Beach check

Homework Solve equations using specific heat formula.