Gr.11 T3 Chemistry (energy+chemical change, gases) Flashcards
Activation energy
The minimum amount of energy required to make a reaction happen
Bond energy
The amount of energy needed to break the bonds in a molecule
Catalyst
A substance that increases the rate of the reaction by lowering the activation energy.
Enthalpy
The total energy of a system.
Chemical potential energy
Energy due to the relative positions of atoms
What happens to enthalpy when wood burns?
Enthalpy of the system decreases, so heat energy is given off (NB!)
Endothermic reaction
Products contain more chemical potential energy than reactants.
What is the symbol for enthalpy ?
H
Define combustion of fuels
An exothermic reaction if a substance reacts rapidly with oxygen
Fuel
A substance that releases energy when it burns
What is an ideal gas?
A hypothetical gas that obeys all the gas laws
What is the ideal gas model? (5)
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
Define temperature of a gas
A measure of the average kinetic energy of all the molecules in that gas
Pressure of a gas
A result of the collisions of particles with the sides of the container
What happens at 0 Kelvin?
Particles don’t move or exert pressure
State Boyle’s Law
The volume of a given gas is inversely proportional to the pressure exerted on it, at a constant temperature
What formula represents Boyle’s Law?
p1V1 =p2V2
Explain Boyle’s Law using the Kinetic Molecular Theory
Volume decreased
Less space for molecules to move
Collide more with walls of container in same amount of time
Pressure increases
T versus t?
T: temperature in Kelvin
t: temperature in degrees Celcius
State Charles’ Law
The volume of a given gas, at constant pressure, is directly proportional to its temperature (K)
State the Gay-Lussac relationship
Won’t be asked in tests
The pressure of an enclosed mass of gas is directly proportional to the temperature (K) of the gas for constant volume
What formula represents Charles’ Law?
V1 V2
– = –
T1 T2
What formula represents the Gay-Lussac relationship?
p1 p2
– = –
T1 T2
What is the air pressure at sea level?
101,3 kPa
Explain Charles’ Law using the Kinetic Molecular Theory
Volume decreases Less space for molecules to move Collide more in same amount of time Average kinetic energy increases Energy increases, so temperature increases
Give the units of measurement for the following formula:
pV=nRT
p: Pa V: m3 n: mol R: 8,31 (unit unimportant) T: K
What shows us the change in enthalpy?
the heat of a reaction (at constant pressure)
How does ice cool something down?
Ice melts
Heat energy absorbed from surroundings
Surrounding get colder
Why does panting cool a dog down?
Water evaporates from tongue
Heat taken from surroundings
Dog cools down
Give an application of exothermic and endothermic reactions.
Cold packs (endothermic) Hot packs (exothermic) Self-heating cups (exothermic)
The Kinetic Molecular Theory
Explains observed changes in terms of position and speed of particles
Fill the gap:
1 Pa = 1 ____
-2
N.m
Fill the gap:
1 bar = ____ kPa
100 kPa
Fill the gap:
-3
1 kPa = ____ N.m
1000
What can be used to measure pressure?
A pressure meter/ pressure guage
