Thermochemistry

Question 1

Thermochemistry

Answer 1

The study of ENERGY changes that occur during chemical REACTIONS and changes of STATE.

Question 2

Chemical Potential Energy

Answer 2

POTENTIAL energy is the energy stored within the chemical BONDS.

Question 3

Heat

Answer 3

ENERGY that is TRANSFERRED from object to object, because there is an energy difference between them.

Question 4

Law of Conservation of Energy

Answer 4

Energy is CONSERVED during a chemical reaction.

Question 5

System

Answer 5

The aspect of the universe that your FOCUS is on.

Question 6

Surroundings

Answer 6

Everything else - IMMEDIATE area around the system.

Question 7

Endothermic Process

Answer 7

A change in which ENERGY is ABSORBED from the surroundings, by the system. This INCREASES the PE of the system and makes it feel COLD.

Question 8

Exothermic Process

Answer 8

System —> Surroundings. DECREASES the PE of the system and makes it feel HOT.

Question 9

Heat Capacity (q)

Answer 9

The AMOUNT of heat needed to increase the temp of an object exactly 1 degree C. Depends on MASS and COMPOSITION.

Question 10

To solve for q…use which equation?

1. Given mass
2. Given volume

Answer 10

1. q=mcdeltat

2. q=vcdeltat

Question 11

Energy is measured in…

Answer 11

J, NOT grams.

Question 12

Energy can only be detected by…

Answer 12

It’s effects.

Question 13

During a chemical reaction, a substance is transformed into a _____, with ____ energies.

Answer 13

Differerent substance, different energies.

Question 14

The variable given to heat is…measured in…

Answer 14

Q in Joules.

Question 15

Heat flows from…to…

Answer 15

A warmer substance to a cooler one.

Question 16

A person sitting beside a fire in a(n) ___ reaction.

Answer 16

Endothermic. Person is system which is absorbing heat

Question 17

The law of conservation of energy states that…

Answer 17

Energy can neither be created nor destroyed.

Question 18

The heat capacity of an object depends on…

Answer 18

Both it’s mass and composition.

Question 19

Hfus= -____

Answer 19

Hsolid

Question 20

Hvap= -___

Answer 20

Hcond

Question 21

Melting and vaporizarion are….

Answer 21

Endothermic processes.

Question 22

Freezing and solidification are…

Answer 22

Exothermic processes.

Question 23

Key points of endothermic processes (7)

Answer 23

1. Heat in reactants
   2.Fusion (Solid —> Liquid)
   Vaporization (Liquid –> Gas)
   3.Reactants low PE, products high PE
   4.Bonds break
2. Energy is absorbed
   6.System is COLD
3. • H value

Question 24

Keys points of exothermic processes (7)

Answer 24

1. Heat in products
   2.Condensation (Gas –> Liquid)
   Solidification (Liquid –> Solid)
2. Reactants high PE, products low PE
   4.Bonds form
3. Energy is released
   6.System is HOT
4. -H value

Question 25

Enthalpy

Answer 25

The TOTAL amount of energy associated with a substance or reaction.

Question 26

Calorimetry

Answer 26

The process of measuring energy changes using a calorimeter, which is a closed system.

Question 27

Heat lost =

Answer 27

Heat gained

Question 28

Molar Heat of Solution

Answer 28

The enthalpy change caused by the dissociation of one mole of substance. (Hsoln)

Question 29

Warming or cooling

Answer 29

1. Involves change in temp and specific heat capacity.
2. q=mcdeltat
3. Change in kinetic energy

Question 30

Phase change

Answer 30

1. Involves no change in temp and energy or removed.
2. Change in PE
3. Hvap(or other) =nH(phase change)

Question 31

Hess’s Law of Summation

Reasoning

Answer 31

• Not every reaction of interst can be studied by means of -calorimetry.
• Reactions are slow (rusting of iron) and products vary (formation of carbon monixide).