Unit: Thermochemistry

Heat, Temperature, Energy Conversions

Day 1 - Notes

After today you will be able to…

• Explain what thermochemistry is• List different types of energy• Explain what happens to particle

motion when heat energy is added

• Convert between units of calories (cal), Joules (J) , and kilo-Joules (kJ)

Thermochemistry: The study of heat changes that occur during chemical reactions and physical changes of state.

Energy: The ability to do work or supply heat.

Different Forms of Energy

•Kinetic•Potential•Heat•Solar

•Nuclear•Wind•Sound•Magnetic

Heat: (q) a form of energy• Flows from warmer objects to cooler

objects• If two objects come into contact

with one another, heat will move from the warmer object to the cooler object until they are the same temperature.

-At this point, equilibrium is reached.

When you add heat energy, molecules move faster; temperature increases.•Temperature: a measure of heat, increase heat, increase temperature

Chemical Potential Energy: stored energy in chemical bonds•Depends on the type of atoms and arrangement

In a chemical reaction, either:• PE is converted to heat (heat

is given off – feels hot, exothermic)• Heat is absorbed and

converted to PE (feels cool, endothermic)

Law of Conservation of Energy: Energy can neither be created nor destroyed, only converted from one form to another.

Units of Energy:•Joule (J)•calorie (cal): chemistry calorie!•Calorie (Cal): food calorie

- 1 food Cal = 1000 chemistry cal- 1 cal = 4.184J

Conversions between energy units:

Example: How many calories are in 287J?K: 287 J

U: ? cal287 J

1 4.184 J

1 cal 68.6 cal

x =

Conversions between energy units:

Example: How many kJ are equal to 1478cal?K:

1478calU: ? kJ

1478 cal 1 1 cal

4.184 J

6.184 kJx =x1000 J

1 kJ

Questions?Complete

WS 1