thermochemistry

Question 1

Energy

• potential energy
• kinetic energy

Answer 1

:the capacity to supply heat or do work

• the energy an object has because of its relative position, composition, or condition
• the energy that an object possesses because of its motion

Question 2

Law of conservation of energy

Answer 2

during a chemical or physical change, energy can be neither created nor destroyed, although its form can change.

Question 3

Heat(q)

Heat flow

Answer 3

• is the transfer or thermalenergy between two bodies at different temperatures
• ( a redundant term, but no one commonly used) increases the thermal energy of one body and decreases the thermal energy of the other.

Question 4

Thermal energy

Temperature

Answer 4

• kinetic energy (KE) associated with the random motion of atoms and molecules.
• quantitative measure of ¨hot¨ or ¨cold¨.
• more fast-moving molecules→high thermal energy→¨hot¨
• more slow-moving molecules→low thermal energy→¨cold¨

Question 5

exothermic process

endothermic process

Answer 5

• a change that releases heat
  example: the combustion reaction that occurs when using an exycetylene torch.
• a change that absorbs heat
  example: the reaction in a cold pack used to treat muscle strains

Question 6

calories(cal)

a joule(J)

Answer 6

• amount of energy required to raise one gram of water by 1°C (or 1 Kelvin)
• amouth of energy used when a force of 1 newton moves an object 1 meter

Question 7

value of q is postive

value of q is negative

Answer 7

• substance gains thermal energy, T final > T initial
• substance loses thermal energy, T final < T initial

Question 8

heat capacity (C)

specific heat capacity (c)

Answer 8

• quantity of heat (q) it absorbs or releases when it it experiencs a temperature change (♦T) of 1°C (or 1 Kelvin)
• quantity of heat required to raise the temperature of 1 gram of a subtance by 1 °C (or 1 Kelvin)

Question 9

Calorimetry

Answer 9

measure the amount of heat transferred to or from a substance

Question 10

system

surroundings

the universe

Answer 10

• subtance or substances undergoing the chemical or physical change
• all other matter
• system + surroundings

Question 11

Metal liquid heat transfer

Answer 11

hot piece of metal (M) and cool water (W)

heat will transfer from M to W

temperature of M will decrease, W will increase

heat exchange is only between M and W.

The net exchange in heat is zero

q_m+q_w=0

q_m=-q_w

The heat of both substances is equal in magnitude but opposite in sign

Question 12

calorimeter

Answer 12

• device used to measure the amount of heat involved in a chenical or physical process.
• coffee-cup calorimeters, are often used in general chemistry labs
• commerical calorimeters of better design are used in industry and for research

Question 13

reaction solution heat transfer

Answer 13

qreaction + qsolution = 0

qreaction = -qsolution

Question 14

internal energy (U), E

the first law of thermodynamics

Answer 14

the total of all possible kinds of energy present in a substance

♦U = q + w

-where w is the work done on (or by) the system, and w=-P -W when a gas expands against a constant external pressure

Question 15

energy can be transported into a system, resulting in an increase in internal energy

energy can also be transferred out of a system, resulting in a decrease in internal energy

Answer 15

• the system absorbs heat from the surroundings: +q
• or the surroundings do work on the system: +w
• the system releases heat to the surroundings: -q
• or the system does work on the surroundings: -w