4.1 Deformation of Solids Flashcards
Define
Mole
The mole is the amount of substance which contains as many particles (atoms or molecules) as there are atoms in 12g (0.012kg) of Carbon-12.
Equation
Moles
num of moles = total number of molectules⁄Avogadro constant
OR
number of moles = total mass⁄molar mass
Absolute zero
- The temperatuyre zero Kelvin is called absolute zero.
- It is the lowest temperature possible.
- At this temperature the gas molecules have zero KE, i.e. absolute zero is the temperature at which all molecular motion stops.
Define
Interal energy
Internal energy is the random distribution of kinetic and potential energy amongst the molecules of a substance,
Experiment
Charles’ Law
Considerations
- Air is trapped inside a capillary tube by a short length of concentrated sulphuric acid.
- As the cross-sectional area of the capillary tube is uniform, the length of the air column is directly proportional to the volume. Hence the length of the trapped air can be used in place of the volume of the air (volume = length x CSA).
- Rubber bands hold the capillary tube in place on the ruler and the bottom of the tube is positioned level with the zero on the ruler scale.
- The open end of the tube ensures that pressure remains constant throughout the experiment (atmospheric pressure + pressure of sulphuric acid column).
Carrying out
- The capillary tube, ruler and thermometer are placed in a beaker of water.
- The water is gently heated and stirred frequently, allowing the trapped air in the capillary tube to reach the temperature of the surrounding water.
- Corresponding readings of temperature and volume (or length) are taken for the air column at regular temperature intervals and recorded. e.g. 10°C
- The readings are then plotted on a graph of volume (or length) against temperature and analysed.
State
Charles’ Law
in words
The volume of a fixed mass of gas is directly proportional to its temperature in Kelvin if the pressure remains constant.
Equation
Charles’ Law
V⁄T = Constant
OR
V1⁄T1 = V2⁄T2
V is gas volume
T is temperature in Kelvin
Experiment
Boyle’s Law
Considerations
- The oil traps a fixed mass of gas (air) in the strong, closed glass tube.
- A car foot pump is used to increase the pressure which is measured / read using a (Bourdon) pressure gauge.
- A valve is used to maintain or release the pressure.
Carrying out
- The pressure of the trapped air is varied by using the foot pump (and valve) and then left for about 1 minute to allow it to return to room temperature before any results are taken (temperature must remain constant - i.e. compressing the gas warms it slightly).
- Each time the pressure is changed the reading on the pressure gauge is recorded and the corresponding volume of the trapped air is measured (using either a calibrated scale or by using the length of the air column to represent the volume in arbitrary units -as previously explained, the volume is directly proportional to length because the cross-sectional area of the glass tube is uniform).
- The readings for volume (or length) and pressure are then used to plot graphs of:
- Pressure on the x-axis against volume (or length) of air column on the y-axis.
- Pressure on the x-axis against volume-1 (or length-1) on the y-axis.
State
Boyle’s Law
in words
The volume of a fixed mass of gas is inversely proportional to its pressure if the temperature remains constant.
Equation
Boyle’s Law
pV = constant
OR
p1V1 = p2V2
p is the gas pressure
V is the gas volume
Experiment
The Pressure Law
Considerations
- The glass flask may expand a little on heating, allowing the gas to expand also (i.e. volume may not be perfectly constant).
- The tubing leading to the pressure gauge is not in the water bath, so the temperature of the air in this is not the same as the air in the flask. To minimise this, the tube should be as short as possible.
- The air temperature is not exactly the same as the water temperature.
Carrying out
- The glass flask and tubing leading to the pressure gauge trap a fixed mass of gas at constant volume.
- The flask is placed in a water bath which is gently heated and the water is regularly stirred to ensure an even temperature distribution. This brings the air in the glass flask quickly to approximately the same temperature as the water.
- As the temperature rises, the temperature and the corresponding pressure are measured and recorded at regular intervals (e.g. every 10°C, until water starts to boil).
- A graph is plotted of pressure (y-axis) against temperature (x-axis) and analysed.
State
The Pessure Law
in words
The pressure of a fixed mass of gas is directly proportional to its temperature in Kelvin if its volume remains constant.
Equation
Pressure Law
p⁄T = constant
OR
p1⁄T1 = p2⁄T2
p is the gas pressure
T is the temperature in Kelvin
Equation
The Gas Equation
p1V1⁄T1 = p2V2⁄T2
The temperature must be in Kelvin.
The mass of the gas must be constant.
The temperature must be in Kelvin.
The units of p and V must be the same on both sides.
Equation
Ideal Gas Equation
pV = nRT
OR
pV = NkT
p is the gas pressure
V is the gas volume
n is the number of moles
N is the total number of gas molecules
R is the molar gas constant
k is the Boltzmann constant
T is the gas temperature in Kelvin
Equation
Kinetic Theory of Gases
pV = 1⁄3Nm<c2>
p is the pressure of the gas
V is the volume of the gas
N is the number of gas molecules
m is the mass of a single gas molecule
<c2> is the mean squared speed of the gas molecules
Equation
Mean speed (<c>)
<c> = c1 + c2 + c3 + … + cN⁄N
Equation
Mean square speed (<c2>)
<c2> = c12 + c22 + c32 + … + cN2⁄N
Equation
Root mean square speed (crms)
crms = √c12 + c22 + c32 + … + cN2⁄N
OR
crms = √<c2>
Equation
Gas density
p = 1⁄3ρ<c2>
p is the gas pressure
ρ is the density of the gas
Define
Specific Heat Capacity
The specific heat capacity of a material is the amount of heat energy needed to raise the temperature of 1kg of the material by 1K.
Equation
Specific Heat Capacity
Q = mc∆θ
Q is the amount of heat energy supplied
m is the mass of the material
∆θ is the change of temperature
c is the specific heat capacity
