Free KCSE Physics Topical Questions KNEC Standards

K.C.S.E Physics Q & A - MODEL 2019PP1QN18

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN18

(a) Figure 9 shows a graph of pressure against temperature for a fixed mass of gas at constant volume.

From the graph, determine the values of n arid e given that P = nT + c where n and c are constants.
(b) Explain why it is not possible to obtain zero pressure of a gas in real life situation.
(c) A fixed mass of a gas occupies 1.5 X 10^-3 m^-3 at a pressure of 760 mmHg and a temperature of 273 K. Determine the volume the gas will occupy at a temperature of 290K and a pressure of 720 mmHg.
(d) State any three assumptions made in kinetic theory of gases.

answers

(b) It is not possible to reduce the pressure of a gas to zero since by then most of the temperatures are very low hence the gas liquefies.

(d) Assumptions of the kinetic theory of gases:
Attraction of between the molecules is negligible.
Volume of the molecule is negligible compared to the volume of the container occupied by the gas.
The molecules undergo elastic collisions.
The length of time of a collision is negligible compared to the time between collisions.

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K.C.S.E Physics Q & A - MODEL 2018PP1QN18

29/7/2020

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K.C.S.E Physics Q & A - MODEL 2018PP1QN18

(a) State two quantities that must be kept constant in order to verify Boyle’s law.
(b) An air bubble at the bottom of a beaker full of water becomes larger as it rises to the surface. State the reason why;
(i) the bubble rises to the surface,
(ii) It becomes larger as it rises.
(c) State two assumptions made in explaining the gas laws using the kinetic theory of gases.
(d) Figure 11 shows an incomplete experimental set up that was prepared by a student to verify one of the gas laws.

(i) State with a reason which one of the laws may be verified using the set up.
(ii) State what the student left out in the diagram of the set up.
(c) The volume of a fixed mass of a gas reduced from 500 cm³ to 300 cm³ at constant pressure. The initial temperature was 90K. Determine the final temperature

answers

(a) Mass
Temperature
(b)(i) The gas is less dense than the water.
(ii) As it rises the pressure around the bubble reduces and since the temperature is the same, the volume increases.
(c) The size of the molecules is assumed to be negligible.
Intermolecular forces are also assumed to be negligible.
Real gases can never have zero volume yet the gas laws assume presence of zero volume.
(d)(i) The pressure law.
Has ability to measure the temperature and the pressure while keeping the volume constant.
(ii) Source of heating for the temperature to be changed.

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K.C.S.E Physics Q & A - MODEL 2018PP1QN10

28/7/2020

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K.C.S.E Physics Q & A - MODEL 2018PP1QN10

Figure 6 Shows the relationsh1 between Volume and pressure for a certain gas.

Name the law that the gas obeys.

answer

Boy1e’s law.

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State one assumption for the experiments carried out to verify the gas laws.

28/7/2020

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K.C.S.E Physics Q & A - MODEL 2017PP1QN10

State one assumption for the experiments carried out to verify the gas laws.

answer

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K.C.S.E Physics Q & A - MODEL 2016PP1QN15

27/7/2020

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K.C.S.E Physics Q & A - MODEL 2016PP1QN15

(a) State what is meant by an ideal gas
(b) The pressure acting on a gas in a container was changed steadily while the temperature of the gas maintained constant. The value of volume V of the gas was measured for various values of pressure. The graph in figure 11 shows the relation between the pressure, p and the reciprocal of volume 1/v

(i) Suggest how the temperature of the gas could be kept constant
(ii) Given that the relation between the pressure P1 and the volume, V₁ of the gas is given by PV = k, where k is a constant, use the graph to determine the value of k.
(iii) What physical quantity does k represent?
(iv)State one precaution you would take when performing such an experiment
(c) A gas occupies a volume of 4000 litres at a temperature of 37⁰C and normal atmospheric pressure. Determine the new volume of the gas if it is heated at constant pressure to a temperature of 67⁰C (normal atmospheric pressure P= 1.01 x 10⁵ pa)

answers

(a)A gas that obeys the gas laws perfectly
(b) (i)By changing pressure very slowly or by allowing gas to go to original temperature after each change

(iii)Work done on the gas
(iv)Use dry gas
Make very small changes in pressure

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K.C.S.E Physics Q & A - MODEL 2015PP1QN17

24/7/2020

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K.C.S.E Physics Q & A - MODEL 2015PP1QN17

(a) Figure 11 shows a graph of pressure (p) against volume (y) for a fixed mass of a gas at constant temperature

In the space provided, sketch the corresponding graph of p against 1/v.
(b) Explain the pressure law using the kinetic theory of gases.
(c) 20 cm3 of a gas exerts a pressure of 760 mmHg at 25°C. Determine the temperature of the gas when the pressure increases to 900 mmHg and the volume reduces to 15 cm3.
(d) Figure 12 shows the path of a light ball projected horizontally.

The ball is then made to spin in an anticlockwise direction as it moves:
(i) on the same axis, sketch the new path of the ball.
(ii) explain how the ball attains the new path

answers

(b) -P/T = constant at constant volume
as temperature increases, the kinetic energy of the molecules increases causing more collisions hence increased pressure.

(ii) Spinning causes high velocity of air above the ball hence reduced pressure which causes the ball to rise higher.

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K.C.S.E Physics Q & A - MODEL 2014PP1QN12

23/7/2020

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K.C.S.E Physics Q & A - MODEL 2014PP1QN12

On the axis provided, sketch the graph which shows the relationship between volume and temperature of a fixed mass of water in the temperature range 0°C to 10°C

answer

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K.C.S.E Physics Q & A - MODEL 2013PP1QN17

22/7/2020

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K.C.S.E Physics Q & A - MODEL 2013PP1QN17

Figure 11 shows an insulated cylinder fitted with a pressure gauge, a heating coil and a frictionless piston of cross-sectional area 100 cm².

(a) While the piston is at position O, the pressure of the enclosed gas is 10 Ncm^-2 at a temperature of 27°C. When a 10 kg mass is placed on the piston, it comes to rest at position A without change in the temperature of the gas.
(1) Determine the new reading on the pressure gauge.
(ii) State with a reason how the value obtained in (i) compares with the initial pressure.
(b) The gas is now heated by the heating coil so that the piston moves back to the original position O.
(î) State the reading on the pressure gauge.
(ii) Determine the temperature of the gas in oc.
(Take g = 10 Nkg^-1).

answers

(ii) Pressure has increased; because, when the volume reduces, the collisions between the gas molecules and walls of the container increases;

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K.C.S.E Physics Q & A - MODEL 2012PP1QN15

21/7/2020

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K.C.S.E Physics Q & A - MODEL 2012PP1QN15

(a) Figure 6 shows a graph of volume against temperature for a given mass of gas.

Use the graph to determine the absolute zero temperature in 0c.
(b) Figure 7 shows a horizontal tube containing air trapped by a mercury thread of length 24 cm. The length of the enclosed air column is 15 cm. The atmospheric pressure is 76 cm Hg.

(i) State the pressure of the enclosed air.
(ii)The tube is now held in a vertical position with the open end facing upwards as shown in Figure 8

Determine:
(i) The pressure of the enclosed air.
(II) The length (l) of the enclosed air column.
(c) In an experiment to demonstrate atmospheric pressure, a plastic bottle is partially filled with hot water and the bottle is then tightly corked. After some time the bottle starts to get deformed.
(i) State the purpose of the hot water.
(ii) State the reason why the bottle gets deformed.
(iii) Explain your answer in c (ii)

answers

(ii) (I) When vertical,
pressure of air = pressure due to mercury column-i-atmospheric pressure
= (24+76)cmHg
= lOOcmHg;

(c) (i) To expel air;
(ii) Pressure of air outside the bottle is greater than the pressure of air inside;
(iii) Cooling causes condensation of vapour;
Creating a partial vacuum;

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K.C.S.E Physics Q & A - MODEL 2012PP1QN08

20/7/2020

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K.C.S.E Physics Q & A - MODEL 2012PP1QN08

In verifying the pressure law of gases, the temperature and pressure of a gas are varied at constant volume. State the condition necessary for the law to hold.

ANSWER

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When the temperature of a gas in a closed container is raised, the pressure of the gas increases. Explain how the molecules of the gas cause the increase in pressure.

19/7/2020

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K.C.S.E Physics Q & A - MODEL 2011PP1QN08

When the temperature of a gas in a closed container is raised, the pressure of the gas increases. Explain how the molecules of the gas cause the increase in pressure.

ANSWER

Speed of molecules increases;
Molecules hit walls more frequently with greater momentum.

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K.C.S.E Physics Q & A - MODEL 2009PP1QN18

17/7/2020

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K.C.S.E Physics Q & A - MODEL 2009PP1QN18

(a) State the pressure law for an ideal gas
(b) An air bubble is released at the bottom of a tall jar containing a liquid. The height of the liquid column is 80 cm. The volume of the bubble increases from 0.5 cm³ at the bottom of the liquid to 1. 15 cm³ at the top. Figure 11 shows the variations of pressure, P, on the bubble with the reciprocal of volume 1/v, as it rises in the liquid.

(i) State the reason why the volume increases as the bubble rises in the liquid Column
(ii) From the graph, determine the pressure on the bubble:
(I) At the bottom of the liquid column;
(II) At the top of the liquid column
(iii) Hence determine the density of the liquid in kgm^-3
(iv) What is the value of the atmospheric pressure of the surrounding?
(c) A rubber tube is inflated to pressure of 2.7 x 10⁵ Pa and volume 3800 cm³ at a temperature of 25⁰C. It is then taken to another place where the temperature is 15⁰C and the pressure 2.5 x 10⁵ Pa. Determine the new volume.

answers

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K.C.S.E Physics Q & A - MODEL 2009PP1QN13

17/7/2020

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K.C.S.E Physics Q & A - MODEL 2009PP1QN13

State what is meant by absolute zero temperature (zero Kelvin or 273⁰C)

ANSWER

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K.C.S.E Physics Q & A - MODEL 2008PP1QN17

16/7/2020

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K.C.S.E Physics Q & A - MODEL 2008PP1QN17

a) What is meant by absolute zero temperature?
Fig. 10 shows a set up to investigate the relationship between temperature and volume for a certain gas.

b) State two factors that are kept constant, in order to determine the relationship.
c) The graph in Fig. 11 shows the relationship between volume and temperature for the experiment.

(i) What was the volume of the gas at 0⁰C?
(ii) At what temperature would the volume of the gas be zero?
(iii) Explain why the temperature in part (ii) above cannot be achieved.
d) A sealed gas cylinder contains 300cm³ of certain gas at a temperature of 25⁰C, and at a pressure of 9.5x 10⁴pa. the gas in the cylinder was then cooled to 10⁰C.
Determine the new pressure of the gas in the cylinder.

answers

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K.C.S.E Physics Q & A - MODEL 2007PP1QN12&13

15/7/2020

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K.C.S.E Physics Q & A - MODEL 2007PP1QN12&13

The graph in figure 7 shows the relationship between the pressure and temperature for an ideal gas. Use the information in the figure to answer questions 12 and 13

State the unit of the horizontally axis
Write a statement of the gas law represented by the relationship

answer

12. Kelvin (K) in words ( one triangle used follow)
13. The pressure of a fixed mass of a gas is directly proportional to its absolute ( Kelvin temperature provided the volume is kept constant P & T volume constant

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K.C.S.E Physics Q & A - MODEL 2006PP1QN16

14/7/2020

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K.C.S.E Physics Q & A - MODEL 2006PP1QN16

(a) State what is meant by an ideal gas
(b) The pressure acting on a gas in a container was changed steadily while the temperature of the gas maintained constant. The value of volume V of the gas was measured for various values of pressure. The graph in figure 9 shows the relation between the pressure, p and the reciprocal of volume 1

(i) Suggest how the temperature of the gas could be kept constant
(ii) Given that the relation between the pressure P1 and the volume, V1 of the gas is given by
PV = k
When k is a constant, use the graph to determine the value of k.
(iii) What physical quantity does k represent?
(iv) State one precautions you would take when performing such an experiment
(c) A gas occupies a volume of 4000 litres at a temperature of 37⁰C and normal atmospheric pressure. Determine the new volume of the gas if it heated at constant pressure to a temperature of 67⁰C (normal atmospheric pressure P= 1.01 x 10⁵ pa)

ANSWERS

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K.C.S.E Physics Q & A - MODEL 2006PP1QN09

14/7/2020

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K.C.S.E Physics Q & A - MODEL 2006PP1QN09

On the axes provided sketch the graph of pressure P against volume V for a fixed mass of an ideal gas.

answer

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K.C.S.E Physics Q & A - MODEL 2005PP1QN27

13/7/2020

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K.C.S.E Physics Q & A - MODEL 2005PP1QN27

The melting point of oxygen is given as -281.3⁰C. Covert this temperature to Kelvin (K)

ANSWER

273+ -281.3 = 8.3K

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K.C.S.E Physics Q & A - MODEL 2004PP1QN27

12/7/2020

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K.C.S.E Physics Q & A - MODEL 2004PP1QN27

A balloon is filled with air to volume of 200ml at a temperature of 293K. Determine the volume when the temperature rises to 353K at the voltmeter, V.

answer

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K.C.S.E Physics Q & A - MODEL 2003PP1QN24

11/7/2020

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K.C.S.E Physics Q & A - MODEL 2003PP1QN24

On the axes provided in Fig. 13, sketch a graph of pressure(p) against reciprocal of volume(1/V) for a fixed mass of an ideal gas at constant temperature.

answer

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K.C.S.E Physics Q & A - MODEL 2002PP1QN22

10/7/2020

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K.C.S.E Physics Q & A - MODEL 2002PP1QN22

On the axes provided sketch the P-V graph for a gas obeying Boyle's law.

answer

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K.C.S.E Physics Q & A - MODEL 2001PP2QN07

9/7/2020

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K.C.S.E Physics Q & A - MODEL 2001PP2QN07

ai) State the pressure law of an ideal gas.
ii) The pressure p, of a fixed mass of a gas at constant temperature T= 300K is varied continuously. The corresponding values of P and the volume V of the gas are shown in table 2.

Given that PV = 2RT where R is a constant, plot an appropriate graph and use it to determine r.

b) A tin closed with an airtight lid contains air at a pressure of 1.0 x 10⁵+ Pa and temperature of 12 C. The tin is heated in a water bath until the lid opens. If the temperature at which the lid opens is 88C, determine the pressure attained by the gas. (Ignore expansion of the tin).

answers

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K.C.S.E Physics Q & A - MODEL 2000PP2QN03

8/7/2020

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K.C.S.E Physics Q & A - MODEL 2000PP2QN03

a) Using the kinetic theory of gases, explain how a rise in the temperature of a gas causes a rise in the pressure of the gas if the volume is kept constant.
b) Fig. 5 shows a set up that may be used to verify Charles Law.

i) State the measurements that should be taken in the experiment.
ii) Explain how the measurements taken in (i) above, may be used to verify Charles Law.
iii) What is the purpose of the water bath.
c) A certain mass of hydrogen gas occupies a volume of 1 .6m³ at a pressure of 1.5 x10⁵ pa and temperature 12°C. Determine its volume when the temperature is 0°C at a pressure of 1.0 x 10⁵ pa.

answers

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State the reason why gases are easily compressible while liquids are solids are not?

8/7/2020

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K.C.S.E Physics Q & A - MODEL 2000PP1QN06

State the reason why gases are easily compressible while liquids are solids are not?

ANSWER

Particles of gases are relatively far apart while those of liquids and liquids are closely parked

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K.C.S.E Physics Q & A - MODEL 1999PP1QN27

7/7/2020

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K.C.S.E Physics Q & A - MODEL 1999PP1QN27

Determine the pressure required to compress a gas in a cylinder initially at 20C and at a pressure 1.03 x 10^-5 to one-eight of its original volume.

ANSWER

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K.C.S.E Physics Q & A - MODEL 2019PP1QN18

K.C.S.E Physics Q & A - MODEL 2018PP1QN18

K.C.S.E Physics Q & A - MODEL 2018PP1QN10

State one assumption for the experiments carried out to verify the gas laws.

K.C.S.E Physics Q & A - MODEL 2016PP1QN15

K.C.S.E Physics Q & A - MODEL 2015PP1QN17

K.C.S.E Physics Q & A - MODEL 2014PP1QN12

K.C.S.E Physics Q & A - MODEL 2013PP1QN17

Figure 11 shows an insulated cylinder fitted with a pressure gauge, a heating coil and a frictionless piston of cross-sectional area 100 cm2.

K.C.S.E Physics Q & A - MODEL 2012PP1QN15

K.C.S.E Physics Q & A - MODEL 2012PP1QN08

When the temperature of a gas in a closed container is raised, the pressure of the gas increases. Explain how the molecules of the gas cause the increase in pressure.

K.C.S.E Physics Q & A - MODEL 2009PP1QN18

K.C.S.E Physics Q & A - MODEL 2009PP1QN13

State what is meant by absolute zero temperature (zero Kelvin or 2730C)

K.C.S.E Physics Q & A - MODEL 2008PP1QN17

K.C.S.E Physics Q & A - MODEL 2007PP1QN12&13

K.C.S.E Physics Q & A - MODEL 2006PP1QN16

K.C.S.E Physics Q & A - MODEL 2006PP1QN09

K.C.S.E Physics Q & A - MODEL 2005PP1QN27

The melting point of oxygen is given as -281.30C. Covert this temperature to Kelvin (K)

K.C.S.E Physics Q & A - MODEL 2004PP1QN27

K.C.S.E Physics Q & A - MODEL 2003PP1QN24

K.C.S.E Physics Q & A - MODEL 2002PP1QN22

K.C.S.E Physics Q & A - MODEL 2001PP2QN07

b) A tin closed with an airtight lid contains air at a pressure of 1.0 x 105+ Pa and temperature of 12 C. The tin is heated in a water bath until the lid opens. If the temperature at which the lid opens is 88C, determine the pressure attained by the gas. (Ignore expansion of the tin).

K.C.S.E Physics Q & A - MODEL 2000PP2QN03

State the reason why gases are easily compressible while liquids are solids are not?

K.C.S.E Physics Q & A - MODEL 1999PP1QN27

Determine the pressure required to compress a gas in a cylinder initially at 20C and at a pressure 1.03 x 10-5 to one-eight of its original volume.

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Figure 11 shows an insulated cylinder fitted with a pressure gauge, a heating coil and a frictionless piston of cross-sectional area 100 cm².

State what is meant by absolute zero temperature (zero Kelvin or 273⁰C)

The melting point of oxygen is given as -281.3⁰C. Covert this temperature to Kelvin (K)

b) A tin closed with an airtight lid contains air at a pressure of 1.0 x 10⁵+ Pa and temperature of 12 C. The tin is heated in a water bath until the lid opens. If the temperature at which the lid opens is 88C, determine the pressure attained by the gas. (Ignore expansion of the tin).

Determine the pressure required to compress a gas in a cylinder initially at 20C and at a pressure 1.03 x 10^-5 to one-eight of its original volume.