Physics Paper 1A, May/June 2012  
Questions: 1 2 3 Main
General Comments

Question 2A

            Question 2


You are provided with a syringe, a petri-dish firmly attached to the base of the movable piston (Plunger) of the syringe, a set of weights and other necessary apparatus.

  1. Pull the piston of the syringe upward until it can no longer move.

Read and record this position of the piston on the graduated mark on the syringe as V,

  1. Clamp the syringe and ensure that it is vertical.
  2. Place a mass M ~ 500g gently at the      centre of the petri-dish
  3. Read and record the new position of the piston as V.
  4. Evaluate V1
  5. Repeat the procedure for four other values of M = 1000 g, 1500 g. ?.000g and       2500g.
  6. Tabulate your readings.
  7. Plot a graph with V on the vertical axis and M on the horizontal axis, starting       both

axes from the origin (0,0).

  1. Determine the slope,s, of the graph.
  2. Evaluate K = s 1
  3. State two precautions taken to ensure accurate results.

(b) (i) When a weight is placed on the petri-dish, which quantities of the gas in the syringe (α) increases,
(β) decreases?

What is responsible for the pressure exerted by a gas in a closed vessel?



Few candidates attempted this question. The few that attempted it were not able to get good graphs as a result of poor readings from the set-up.
Many candidates did not record the initial value of the volume V0. Those that did record it to the wrong number of decimal place e.g.

V0 = 10cm3 instead of 10.00cm3. Few other candidates failed to express v-1 to 3d.p or 3s.f.
However, the values of V were well determined.
Part (b) was poorly handled. Many candidates were unable to state correctly the quantity that increase 0,e pressure) and decrease (i.e volume) nor were they able to use kinetic theory to explain what Is responsible for pressure in the vessel.
The expected answers are:
(jj) Initial volume V0 read and recorded correctly to at least 1 d.p in cm3

  1. Five values of M correctly recorded in gm
  2. Five values of V correctly read and recorded to at least 1 d.p in cm3 and in trend

(Trend: As M increases, V decreases)

  1. Five values of V'1 correctly evaluated to at least 3 d.p
  2. Composite table showing M, V and V1

Candidates are also expected to:
plot five points on graph distinguish between the axes

  1. chose reasonable scales draw line of best fit
  2. determine the slope of the graph
  3. evaluate k = s 1
  4. State any two of the following precautions in acceptable language.
  5. Avoided parallax error in reading the syringe
  6. Syringe was firmly clamped
  7. Repeated readings ( Shown on table)

(b)   (i)       (α) Pressure increases
                     (β) Volume decreases

        (ii)The collision of the molecules of the gas with the walls of the


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