ThermochemistryWhat does temperature measure?

What does pressure measure?

ThermochemistryHeat changes that occur during a chemical

reactionEnergy- the capacity for doing work or

supplying heatEnergy is weightless, colorless, and

odorlessEnergy that is stored in the bonds of

chemical substances is called chemical potential energy. (Example: gasoline)

What is Work and Heat?Work- when a force is used to move an objectHeat- energy that is transferred from one

object to anotherThrough a temperature change

Neither senses nor instruments can detect heat; only changes in heat can be detected

Heat flows from warm to cold until equilibrium is reached

SurroundingsSystem

Key terms for describing the flow of energySystem- part of the

universe you are interested in

Surroundings- everything else in the universe

Universe- the system and the surroundings

The Universe is Everything

EndothermicWhen heat flows

into a system from the surroundings the process is called endothermic+q

ExothermicWhen heat flows

out of a system into the surroundings the process is called exothermic-q

What is a calorie?The quantity of heat

required to raise one (1) gram of water one (1) C

The unit that we will be using that is the SI system of measurement for heat is the joule1 joule = 0.2390 calories1 calorie = 4.184 joules

Heat CapacityThe amount of heat

needed to raise the temperature of substance 1 C

Heat capacity depends on the composition and the mass of the substance

Specific Heat CapacityThe amount of heat it

takes to raise 1 gram of a substance 1 C

We can determine the heat capacity using the equation

C = Specific Heat (J/g C or cal/g C)

q = heat (J or cal)m = mass (g)T = Tfinal – Tinitial (C)

T m

q Cp

ExampleWhen 400 J of heat is

added to 4.0 grams of olive oil at 20C, the temperature increases to 60C. What is the specific heat of olive oil?

C = ?q = 400 Jm = 4.0 gT = Tfinal – Tinitial =

60C – 20C = 40 C

Tm

qC

Cg

JC

400.4

400

Cg

JC

5.2

Another ExampleHow much heat is

required to raise the temperature of 200.0 g of mercury 50 C? The specific heat of mercury is 0.15 J/g C.

C = 0.15 J/g Cq = ? m = 200.0 gT = 50 C

Tm

qC

TmCq

CgCg

Jq

500.20015.0

Jq 1500