Gr.11 T3 Chemistry (energy+chemical change, gases)

Question 1

Activation energy

Answer 1

The minimum amount of energy required to make a reaction happen

Question 2

Bond energy

Answer 2

The amount of energy needed to break the bonds in a molecule

Question 3

Catalyst

Answer 3

A substance that increases the rate of the reaction by lowering the activation energy.

Question 4

Enthalpy

Answer 4

The total energy of a system.

Question 5

Chemical potential energy

Answer 5

Energy due to the relative positions of atoms

Question 6

What happens to enthalpy when wood burns?

Answer 6

Enthalpy of the system decreases, so heat energy is given off (NB!)

Question 7

Endothermic reaction

Answer 7

Products contain more chemical potential energy than reactants.

Question 8

What is the symbol for enthalpy ?

Answer 8

H

Question 9

Define combustion of fuels

Answer 9

An exothermic reaction if a substance reacts rapidly with oxygen

Question 10

Fuel

Answer 10

A substance that releases energy when it burns

Question 11

What is an ideal gas?

Answer 11

A hypothetical gas that obeys all the gas laws

Question 12

What is the ideal gas model? (5)

Answer 12

Particles in continuous motion in all directions

Very small particles - don’t contribute to volume

No forces between molecules/ between container and molecules except when colliding

Collisions are elastic (no energy lost to surroundings)

All molecules are identical

Question 13

Define temperature of a gas

Answer 13

A measure of the average kinetic energy of all the molecules in that gas

Question 14

Pressure of a gas

Answer 14

A result of the collisions of particles with the sides of the container

Question 15

What happens at 0 Kelvin?

Answer 15

Particles don’t move or exert pressure

Question 16

State Boyle’s Law

Answer 16

The volume of a given gas is inversely proportional to the pressure exerted on it, at a constant temperature

Question 17

What formula represents Boyle’s Law?

Answer 17

p1V1 =p2V2

Question 18

Explain Boyle’s Law using the Kinetic Molecular Theory

Answer 18

Volume decreased
Less space for molecules to move
Collide more with walls of container in same amount of time
Pressure increases

Question 19

T versus t?

Answer 19

T: temperature in Kelvin
t: temperature in degrees Celcius

Question 20

State Charles’ Law

Answer 20

The volume of a given gas, at constant pressure, is directly proportional to its temperature (K)

Question 21

State the Gay-Lussac relationship

Won’t be asked in tests

Answer 21

The pressure of an enclosed mass of gas is directly proportional to the temperature (K) of the gas for constant volume

Question 22

What formula represents Charles’ Law?

Answer 22

V1 V2
– = –
T1 T2

Question 23

What formula represents the Gay-Lussac relationship?

Answer 23

p1 p2
– = –
T1 T2

Question 24

What is the air pressure at sea level?

Answer 24

101,3 kPa

Question 25

Explain Charles’ Law using the Kinetic Molecular Theory

Answer 25

Volume decreases
Less space for molecules to move
Collide more in same amount of time 
Average kinetic energy increases
Energy increases, so temperature increases

Question 26

Give the units of measurement for the following formula:

pV=nRT

Answer 26

p: Pa
V: m3
n: mol
R: 8,31 (unit unimportant)
T: K

Question 27

What shows us the change in enthalpy?

Answer 27

the heat of a reaction (at constant pressure)

Question 28

How does ice cool something down?

Answer 28

Ice melts
Heat energy absorbed from surroundings
Surrounding get colder

Question 29

Why does panting cool a dog down?

Answer 29

Water evaporates from tongue
Heat taken from surroundings
Dog cools down

Question 30

Give an application of exothermic and endothermic reactions.

Answer 30

Cold packs (endothermic)
Hot packs (exothermic)
Self-heating cups (exothermic)

Question 31

The Kinetic Molecular Theory

Answer 31

Explains observed changes in terms of position and speed of particles

Question 32

Fill the gap:

1 Pa = 1 ____

Answer 32

-2

N.m

Question 33

Fill the gap:

1 bar = ____ kPa

Answer 33

100 kPa

Question 34

Fill the gap:
-3
1 kPa = ____ N.m

Answer 34

1000

Question 35

What can be used to measure pressure?

Answer 35

A pressure meter/ pressure guage