Chemistry - Chapter 17 Flashcards Preview

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Flashcards in Chemistry - Chapter 17 Deck (35):
1

Thermochemistry

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

2

Chemical Potential Energy

The energy stored in the chemical bonds of a substance

3

Heat

(q), energy that transfers from one object to another because of temperature difference between the objects

4

System

part of the universe on which you focus your attention

5

Surroundings

everything else in the universe

6

Law of Conservation of Energy

states that in any chemical or physical process, energy is neither created nor destroyed

7

Endothermic Process

positive or negative value?

heat is absorbed from the surroundings

Heat flowing into a system from its surroundings = positive

8

Exothermic Process

positive or negative value?

one that releases heat to its surroundings

Heat flowing out of a system into its surroundings = Negative

9

Specific Heat

what else is this called?

amount of heat it takes to raise the temp. of 1g of the substance 1° C

Specific Heat Capacity

10

Calorimetry

measurement of the heat flow into or out of a system for chemical and physical processes

11

calorimeter

the insulated device used to measure the absorption or release of heat in chemical or physical processes

12

enthalpy (H)

accounts for the heat flow of the system at constant pressure

13

molar heat of fusion

heat absorbed by 1 mole of a solid substance as it melts to a liquid at constant temp.

S --> L

14

molar heat of solidification

the heat lost when 1 mole of a liquid substance solidifies at a constant temp.

L --> S

15

molar heat of vaporization

amount of heat required to vaporize 1 mole of a given liquid at constant temp.

L --> G

16

molar heat of condensation

the amount of heat released when 1 mole of vapor condenses at its normal boiling point

G --> L

17

molar heat of solution

the enthalpy change caused by the dissolution of 1 mole of substance

18

Calorie conversions (3)

1 Calorie = 1 Kilocalorie = 1000 calories

19

Calorie

quantity of heat needed to raise the temperature of 1g of pure water at 1°C

20

Joule conversions (2)

1 J = 0.2390 cal
1 cal = 4.184 J

21

Energy

capacity for doing work or producing heat

22

Specific Heat formula

Label the variables (4)

C = [q / (m x ΔT)]

C = specific heat
q = heat (J)
m = mass (g)
ΔT = Tf-Ti

23

How to calculate the heat absorbed / released by the surroundings

Label Variables (2)

qsurr = m x C x ΔT

m = mass of water (g)
C = specific heat of water (J/(g°C)

24

How to calculate the heat absorbed / released by the system

Label Variables (2)

qsys = ΔH = -qsurr = -m x C x ΔT

-m = -mass of water (g)
C = specific heat of water

25

heat capacity

the amount of heat needed to increase the temperature of an object exactly 1°C

26

Thermochemical Equation

a chemical equation that includes the enthalpy change (ΔH)

ex. CaO(s) + H2O(l) --> Ca(OH)2(s) + 65.2kJ

27

Heat of Reaction

the enthalpy (ΔH) change for a chemical equation exactly as it is written

ex. ΔH = -65.2 kj = heat of reaction

28

Heat of Combustion

The heat of reaction for the complete burning of 1 mole of a substance

ex. CH4(g) + 2O2(g) ---> CO2(g) + 2H2O(l) + 890kJ or
CH4(g) + 2O2(g) ---> CO2(g) + 2H20(l) ΔH = -890kJ

29

units for the molar heat of...

kJ / mol

29

What does energy lack? (2)

A mass or volume

30

How is energy detected?

By its effects

31

What determines the amount of energy stored in a substance?

The kind of atoms and the arrangement of the atoms in a substance

32

How does heat flow?

From the warmer object to the colder object

33

Heat capacity depends on....(2)

Mass and chemical composition

34

What has a high specific heat? Low specific heat?

High - water
Low - metals