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Flashcards in Thermodynamics Deck (29)
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1

thermochemistry

study of energy changes that occur during chemical reactions and changes in state

2

Two types of energy

Chemical Potential Energy (PE)
Kinetic Energy (KE)

3

chemical potential energy

energy stored within a chemical bond

4

kinetic energy

energy of motion

5

2 Laws of Thermodynamics

1. law of conservation of energy
2. High energy to low energy; high temperature to low temperature

6

Heat

Form of energy that flows
Always travels from warm areas to cool areas
high kinetic energy areas to low kinetic eergy areas

7

temperature

a measure of average kinetic energy of particles. As the average kinetic energy of the particles increases, the temperature increases

8

Units for heat

Joules (J) Kilojoules (kJ)
calorie (cal) Kilocalories (C)

9

calorie to joule conversion

1 cal = 4.184 J

10

joule to kilojoule
calorie to kilocalorie
conversions

1000 joules = 1 kilojoule
1000 calories = 1 kilocalorie

11

On a heating/cooling curve, the flat surfaces show...

potential energy

12

On a heating/cooling curve, the upward sloping lines show...

kinetic energy

13

Heat capacity

the amount of heat needed to raise the temperature of something 1 degree celcius

14

Heat capacity depends on...

1. how much substance you have (mass)
2. the chemical composition

15

specific heat capacity equation and meaning of variables

q = m*c*delta(T)
q = heat (J)
m = mass (g)
delta(T) = change in temp.
Cp = specific heat capacity

16

Exothermic reaction

the system releases heat to the surroundings

17

Endothermic reaction

the system absorbs heat from the surroundings

18

calorimetry

precise measurement of heat flow in or out of the system during a chemical or physical process

19

Equation for heat of fusion/vaporization and meaning of variables

q = delta(H) * mol
q = heat
mol = moles
delta(H) = enthalpy

20

enthalpy

heat content of a system

21

Heat of fusion (melting)

heat/mole asorbed to melt a substance

22

Heat of vaporization

heat/mol needed to vaporize a substance

23

Thermochemical equation

contains the enthalpy (hea) change when a chemical reaction takes place
can be written two ways

24

In an endothermic reaction, the enthalpy symbol...

is included on the reactant side
written with a plus

25

In an exothermic reaction, the enthalpy symbol...

is included on the product side
written with a negative

26

All decomposition reactants are...

endothermic

27

3 Exothermic phase changes

1. condensation
2. freezing
3. deposition

28

3 endothermic phase changes

1. evaporation
2. melting
3. sublimation

29

Changes that spread molecules out..

take in heat while changes that condense molecules give off heat.