Boyle's and Charles' Laws

Question 1

State Boyle’s Law

Answer 1

The pressure and volume of an ideal gas are inversely proportional when kept at a constant temperature

Question 2

State Charles’ Law

Answer 2

The absolute temperature and volume of a gas are directly proportional when kept at a constant pressure

Question 3

How would you measure the cross sectional area of inside of a syringe

Answer 3

• Remove the plunger and then using a micrometer measure the diameter of the seal
• This value can then be substituted into the circular area equation

Question 4

Why should the clip used to seal the tubing coming from the syringe be as close to the syringe tip as possible

Answer 4

The volume of air trapped in the tubing should be as small as possible so that is negligible in comparison to the volume in the syringe

Question 5

Suggest how a mass hanger could be attached to the plunger of the syringe

Answer 5

• A small piece of string can be tied to the plunger to form a loop
• The hanger can then hook onot this loop

Question 6

Why should the syringe be clamped above the region of the plunger’s motion

Answer 6

• Clamping the syringe can distort the barrel and hinder the motion of the plunger
• By clamping above the region in which the plunger moves, this problem is avoided
• It also ensures that the scale of the syringe isn’t covered by the clamp

Question 7

Why should the syringe be clamped at a relatively high positon

Answer 7

The syringe should be clamped at a height so that the plunger has space to move downwards as masses are added

Question 8

How can the force exerted by the masses by calculated

Answer 8

F = mg

Force = Mass x Gravitational Field Strength

Question 9

How can the pressure exerted by the masses on the air sample be calculated

Answer 9

Pressure = Force / Cross Sectional Area of Plunger

The pressure should then be subtracted from the standard atmospheric pressure

Question 10

State the value of standard atmospheric pressure

Answer 10

101 kPa

Question 11

Describe the relationship that should be found when a graph of 1/V against P is plotted

Answer 11

Pressure and volume are inversely proportioanl so the graph of 1/V against P should be a straight line that passes through the origin

Question 12

Suggest why a straight line may not be produced when plotting a graoh of 1/V against P

Answer 12

• The plunger may have experienced some resistance to its motion as masses were added
• This sticking of the plunger would create error that may result in an inaccurate measured change in volume

Question 13

What safety precautions should be taken when using concentrated sulfuric acid

Answer 13

• Safety googles should be worn to ensure no acid enters your eyes
• Gloves could be worn to ensure there is no contact between the acid and your skin

Question 14

What safety precautions should be taken when working with a hot beaker of water

Answer 14

• Avoid touching the hot beaker with bare hands, ensure it is handled with gloves and take care to avoid spillages
• A heatproof mat should be used to protect the bench

Question 15

What should you do before recording each measurement of water temperature

Answer 15

• You should aways stir the water before taking a temperature measurement
• This means that the reading is an appropriate and accurate reflection of the average temperature of the water in the beaker

Question 16

Explain how an estimate of absolute zero can be obtained from a graph of length of air sample against temperature

Answer 16

• The graph will be of the form
• L = mθ + c
• Substituting values from the graph to obtain c and then rearranging for θ when L = 0 to obtain a value for absolute zero