KCSE 2011 General Science Paper 1 Questions with Marking Scheme

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Answer all the questions in the spaces provided.

    1. Name the branch of biology that deals with the study of animals.(1 mark)
    2. Give two reasons for classifying living organisms.(2 marks)
    3. Give a reason why respiration is important in living organisms. (1 mark)
    1. Name the organelles observed under the light microscope in plant cells but not in animal cells.(2 marks)
    2. State two precautions that should be taken when placing a microscope on a table for use. (2 marks)
  3. In an experiment a solution was poured around a potted plant and left for 24 hours. The set up is as shown below.
    1. State the nature of the solution.
    2. Explain the observations made after the 24 hours.(2 marks)
    1. Name one raw material for photosynthesis. (1 mark)
    2. With the exception of guard cells, how are the upper epidermal cells of a leaf adapted to their function? (2 marks)
    1. Distinguish between ingestion and egestion?(1 mark)
    2. The diagram below represents a villus of the human alimentary canal.
      Name the substances that are absorbed through the structures labelled X and Y.(2 marks)
  6. Explain why a person in a poorly ventilated room with a burning charcoal stove may suffocate to death. (3 marks)
    1. Name the causative agent of pneumonia.(1 mark)
    2. State two characteristics of an efficient respiratory surface which are absent in an amoeba.(2 marks)
    3. How is anaerobic respiration applied in the baking industry?(1 mark)
    1. Explain how euphorbia leaves affect its transpiration.(2 marks)
    2. Explain one adaptation of the root hair to its function. (2 marks)
    1. State two functions of the kidney. (2 marks)
    2. Name two metabolic wastes removed through the skin. (2 marks)
  10. State the effects of vasodilation. (2 marks)

Answer all the questions in this section in the spaces provided.

  1. What is meant by the following terms?
    Valency.(1 mark)
    Electron affinity (1 mark)
  2. The information in the table below gives atomic sizes of elements P, Q and R that belong to the same group in the periodic table. Study it and answer the question that follows. P, Q and R are not the actual symbols of the elements.
    Elements Atomic size (nm)
    Which element has the highest ionisation energy? Explain. (2 marks)
    1. Why is air considered a mixture and not a compound?(1 mark)
    2. Give one similarity between rusting and combustion. (1 mark)
    3. Which reagent will decompose to give oxygen gas in the presence of manganese (IV) oxide? (1 mark)
    4. Carbon (IV) oxide does not support burning yet a piece of burning magnesium ribbon continues to burn in a gas jar full of carbon (IV) oxide. Explain. (1 mark)
    1. Using dots() and crosses (x) to represent electrons, draw the structure of sodium chloride. (Na = 11.0, Cl = 17.0). (2 marks)
    2. Name the type of bond in diamond. (1 mark)
  5. Describe how a student would obtain sand from a mixture of sand and sugar. (2 marks)
    1. State the purpose of pH scale. (1 mark)
    2. Hydrochloric acid is a strong acid. Explain the meaning of a strong acid. (1 mark)
    3. Dilute hydrochloric acid was reacted with solid calcium carbonate in a test tube. Write a balanced chemical equation for the reaction. (1 mark)
    4. Give two disadvantages of washing clothes in hard water using soapy detergents. (2 marks)
    1. Describe a test that can be used to show presence of water in a substance.(2 marks)
    2. Magnesium ribbon reacts slowly with water to form a solution that turns red litmus paper blue. Name the solution formed. (1 mark)
  8. State how the following substances conduct electricity.
    1. Molten calcium chloride.(1 mark)
    2. Graphite.(1 mark)
  9. The diagram below shows some changes in the physical states of matter. Study it and answer the questions that follows.
    1. Name the changes represented by letters R and S. (2 marks)
      R: ..................
      S: ...........
    2. Name the method used to separate coloured substances in a dye.(1 mark)
  10. The grid below represents part of the periodic table. Use it to answer the questions that follow. The letters are not the actual symbols of the elements.
    1. Which letter represents an alkaline earth metal? (1 mark)
    2. Which of the two elements represented by the letters W and Z is reactive. Explain(2 marks)
    3. Write the electron arrangement of the element represented by Y. (1 mark)
    1. Name the type of reaction that occurs when a solution of lead (II) nitrate is added to a solution of sodium sulphate (in a boiling tube).(1 mark)
    2. Write a balanced equation for the reaction that occurs when crystals of sodium nitrate are heated in a test tube.(1 mark)
    3. Give the meaning of an acid salt.(1 mark)

Answer all the questions in this section in the spaces provided.

  1. Figure 1, shows a measuring instrument containing a liquid.
    1. State the name of the instrument.(1 mark)
    2. The reading changes from 26.8cmto 42.5cm after 40 drops of the liquid are released, determine the volume of each drop. (2 marks)
    1. A block of wood is pulled along a horizontal surface. State one factor that determines the magnitude of the frictional force between the block and the surface. (1 mark)
    2. Figure 2 shows a vertical glass tube containing a liquid.
      State a reason for the shape of the meniscus in terms of molecular forces.(2 marks)
    1. Figure 3 shows two identical containers A and B filled with different liquids to the same level
      It is observed that the pressure at the bottom of container B is higher than the pressure at the bottom of container A. State the reason for this observation.(1 mark)
    2. Smoke particles inside a smoke cell are observed to move randomly when viewed through a microscope. Explain this observation. (2 marks)
  4. A student observes that in the morning an overhead electrical power cable is straight and taut. At midday the student observes that the same cable has sagged. Explain these observations. (2 marks)
  5. Figure 4, shows a crystal of potassium permanganate at the bottom of a beaker containing some water.
    It is observed that when the beaker is heated from the bottom, strains of colour rise up from the crystal and curve out as shown. Explain this observation.(3 marks)
  6. Figure 5, shows a uniform meter rule pivoted at the 60cm mark. The rule is balanced when a 40g mass is supported at the 90cm mark.
    1. Show on the diagram the position of the centre of gravity of the metre rule. (1 mark)
    2. Determine the mass of the metre rule.(2 marks)
  7. Figure 6, shows a ball bearing resting on a flat surface.
    1. Name the state of equilibrium of the ball bearing.(1 marks)
    2. State the reason for the answer in (a) above.(2 marks)
  8. A spring extends by 20mm when supporting a mass of 150g. Determine the mass which when supported by the same spring causes an extension of 30mm.(3 marks)
  9. A stone is thrown vertically upwards. Sketch a velocity - time graph for the motion of the stone from the time it is thrown until it comes back to the ground.(2 marks)
  10. A box is lying on the floor of a fast moving lorry, it is observed that when the lorry is suddenly brought to rest, the final position of the box is nearer to the front of the lorry than before. Explain this observation.(2 marks)
  11. Figure 7, shows a pully being used to raise a load.
    1. State the velocity ratio of this machine. (1 mark)
    2. State two factors that reduce the efficiency of this machine. (2 marks)
    1. State the law of floatation. (1 mark)
    2. A ship is made of steel. Explain why the A ship is made of steel. Explain why the ship is able to float on water whose density is less than the density of steel.(2 marks)


    1. Zoology; (1 mark)
    2. To sort and group organisms;
      For uniformity in identification;
      Organise information in an orderly manner to avoid chaos;
      Put Organisms into correct groups to make their study easy.(2 marks)
    3. Production of energy, (1 mark)
    1. Cell wall; chloroplasts, sap vacuole (1 mark)
    2. Hold the microscope firmly with both hands
      (one hand at the arm and the other at the base);
      Place the microscope away from the edge of the table.(2 marks) 
    1. Hypertonic;
      Solution of high concentration.
    2. Through osmosis, the plant lost water to the soil environment, this caused the plant to droop;
      Plant cells lost water -H,O to the high concentration;
      Through osmosis cells flaccid leading to dropping/witting.
    1. Carbon (IV) Oxide; water; (any one correct) (1 mark)
    2. Closely packed to protect inner cells;
      Lack of chloroplasts/transparent to allow light to pass through; the cells are one layer thick/thin in diameter to allow light to penetrate easily;
      (any 2 correct)
    1. Ingestion is taking in food material through the mouth while egestion is the removal of undigested/indigestible food materials thought the anal opening;(2 marks)
      1.  in X glucose/amino acids/vitamins;
      2. in Y fatty acids/glycerol.
  6. Burning charcoal stove reduces the amount of oxygen in the room leading to partial burning; which produce carbon(II) oxide; when inhaled it combines permanently with haemoglobin/blocking uptake of oxygen;(3 mark)
    1. Pneumococcus/Diplococcus pneumoniae/streptococcus pneumonial/stephilococcus auries;(1 mark)
    2. High vascularization; ventilation mechanism;(2 marks)
    3. Produce carbon (IV) oxide that raises dough; (1 mark)
    1. Leaves are tiny/small; reducing the surface area over which transpiration occurs/rate of transpiration is reduced; Thick, shinny cuticle; reduce rate of transpiration; (2 marks)
    2. Elongated cells; to provide a large surface area for nutrients/water absorption;/Thin; to facilitates diffusion of substances;(2 marks) 
    1. Excretion; osmoregulation;(2 marks)
      PH regulation;
      Ionic balance.
    2. Water; salts;(2 marks)
    More blood flows closer to the skin;
    More heat is lost cooling occurs;
  11. Valency - combining power of an element/radical; or number of electron gained or lost by an atom(1 mark)
    Electron affinity - energy released when an atom acquires an electron; (1 mark)
  12. R;
    R is the smallest atom with its outermost electrons near the nucleus hence strongly attracted; (2 marks)
    1. Gases in air are separated by physical means;
    2. Both require oxygen gas;
    3. Hydrogen peroxide;
    4. Magnesium has high affinity for the combined oxygen;heat produced by burning magnesium, decomposes carbon (VI) oxide to carbon and oxygen.(4 marks) 
    2. Covalent bond;(1 mark)
  15. Add water to the mixture, warm and stir, sugar will dissolve;
    Filter the mixture to obtain sand as a residue;
    1. To measure the acidity and alkalinity of a solution;/measure the strengths of acids and Bases.
    2. Strong acid is one that dissociates fully to give more hydrogen ions;
    3. 2HCI + CaCo3(s) — CaCl2(aq) + CO2(g) + H2O(l);
    4. Waste of soap;/not economical
      formation of scum stains on clothes(5 marks)
    1. Use anhydrous Copper (II) Sulphate; if it changes form white to blue when in contact with the substance then water is present; /blue anhydrous cobalt chloride paper of cobalt sulphate to pink
    2. Magnesium hydroxide;(3 marks)
    1. Mobile ions;
    2. Delocalised electrons;
    1. R-freezing/solidifying;
      S - Condensation/liquefying;
    2. Chromatography;/paper chromatography(3 marks)
    1. X;
    2. W;W is an alkali metal
      Z is a noble element which is stable; Since it has an octet structure or is in group VIII
    3. 2.8.7; (4 marks)
    1. double decomposition/precipitation;
    2. 2NaNO3(s) heat 2NaNO2(s) + O2(g);
    3. Salt that contains replaceable hydrogen atoms; (3 marks)
    1. Burette(1 mark)
    2. Vol of 40 drops = 42.5 - 26.8
      = 15.7cm
      Vol of 1 drop= 15.7 /40 = 0.39 = 0.4cm3  (2 marks)
    1. Nature of the surface/roughness/smoothness; Normal reaction.(1 mark)
    2. Attraction forces between molecules of the liquid is less than the attraction of the liquid molecules and glass molecules/adhesive forces are greater than cohesive forces.(2 marks)
    1. Density of B is greater than that of A. (1 mark)
    2. Smoke particles are hit by air molecules which are moving in a (continuos) random motion. (2 marks)
  25. In the morning air is cold and the cable contracts becoming shorter.
    At midday the air is hot and the cable expands becoming longer hence sags. (2 marks)
  26. When heated the water molecules expand and become less dense.
    They rise up and cooler more dense water molecules move downwards.(2 marks)
    The potassium paramagnet colour moves up with the less dense molecules hence the colour strains curve up as the water moves in convectional currents.(1 mark)
    1. at 50cm mark/or on dieagrain.(1 mark)
    2. weight acts at the 50cm mark,
      Clockwise moments = anticlockwise moments
      m x 10 = 40 x 30
      10 m = 1200
      m = 120g  (2 marks)
    1. neutral  (1 mark)
    2. When the ball bearing is slightly tilted, the position of centre of gravity remains unchanged. (2 marks)
  29. K=F/e
    =150 x 10-3x10/20 x 10-3
    M= Ke
    150 x 10-3 x 10     30x10-3
    _______________  x  ________
       20 x 10-3               10
    = 225g
  31.  Before the brakes are applied the box was moving at the same speed as the lorry, It continues moving forward due to its inertia when the brakes are suddenly applied/obeys Newton's first law of motion..(2 marks)
    1. 2.  (1 mark)
    2. -weight of the pulley
      - amount of friction between the pulley and the string.(2 marks)
    1. A floating body displaces its own weight of the fluid in which it floats. (1 mark)
    2. The ship is "hollow" and therefore it's average density is less than that of water.(2 marks)


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