KCSE 2018 General Science Paper 1 with Marking Scheme

QUESTIONS

SECTION A: BIOLOGY (34 marks)
Answer all the questions in this section in the spaces provided

1.                      
   1. Name the Kingdom in which the following organisms are classified.(2 marks)
      

      Organism	Kingdom
      (i) Mould, Yeast, Toad stool
      (ii) Euglena, Amoeba, Plasmodium

   2. Give a reason why excretion is important in living organisms.(1 mark)
2.                          
   1. Give one function of the following organelles:(1 mark)
      1. nucleolus
      2. golgi bodies.(1 mark)
3. An organelle was found to have a diameter of 4.0cm under a light microscope. If it was observed under a magnification of X 300,000, calculate the actual size of the organelle. Show your working.(3 marks)
4. Two potato cylinders of equal size were obtained from the same potato tuber. The cylinders were then lowered into two beakers labelled E and F as shown below. Beaker E contained concentrated salt solution while beaker F contained distilled water. At the start of the experiment the rod was balanced until it was horizontal.
   
   
   1. Give the observation made after 25 minutes.(1 mark)
   2. Explain the observation made after 25 minutes.(3 marks)
5.                              
   1. State the meaning of the following terms as used in animal nutrition:
      1. dentition(1 mark)
      2. dental formula(1 mark)
   2. Below is a dental formula of an animal.
      
      
      1. Calculate the value of Q.(1 mark)
      2. Calculate the total number of molars in the animal's mouth.(2 marks)
6. The figure below represents a transverse section of a plant part.
   
   
   1.                    
      1. Name the part of the plant from which the section was obtained. (1 mark)
      2. Name the class of the plant from which the section was obtained. (1 mark)
      3. Give one reason for your answer in (a) (ii) above. (1 mark)
   2. State the function of the part labelled G. (1 mark)
7. The diagram below shows a model used by students to demonstrate breathing mechanism in mammals.
   
   
   1. State three changes expected on the model when it is used to demonstrate inhalation process.(3 marks)
   2. Which part in the mammalian breathing system is equivalent to the rubber sheet in the model?(1 mark)
8. Study the word equation below and answer the equations that follow.
                                 _H
   Glucose + Oxygen   →  Energy + Carbon (IV) oxide + water
   1. Name the biological process that is represented by the equation (1 mark)
   2. Identify the requirement represented by the letter H.(1 mark)
9. Explain four expected responses when the human body temperature falls below the normal level.(4 marks)
10. Name three excretory products in plants.(3 marks)

SECTION B: CHEMISTRY (33 marks)
Answer all the questions in this section in the spaces provided.

11. Study table 1 and answer the questions that follow. The letters do not represent actual symbols of elements.
    Table 1
    

    Element	Number of Protons	Number of Neutrons	Number of Electrons
    W	3	4	2
    X	19	10	10
    Y	12	12	12
    Z	17	20	17

    1. From the table, identify letters that represent:
       1. A neutral atom of a metal. (1 mark)
       2. An anion. (1 mark)
       3. A neutral atom of a non-metal.(1 mark)
    2. Which letters represent elements that belong to the same group? (1 mark)
12. Study the flow chart in figure 1 and answer the questions that follow.
    
    Figure 1
    1. Identify:
       1. Solid Z. (1 mark)
       2. The black residue. (1 mark)
    2. Write an equation for the decomposition of Z. (1 mark)
13. A student used the set up in figure 2 to investigate electrical conductivity of lead(II) bromide.
    
    Figure 2
    1. When the switch was closed, the bulb did not light. Explain.(1 mark)
    2. What improvement can be done to the set-up for the bulb to light?(1 mark)
14.                      
    1. The pH value of ethanoic acid is higher than that of hydrochloric acid. Explain.(2 marks)
    2. What is meant by softening of water?(1 mark)
15. Figure 3 shows the chromatogram of three substances A, B and C. Study it and answer the questions that follow.
    
    Figure 3
    1. Label the baseline. (1 mark)
    2. From the chromatogram, select a pure substance. (1 mark)
    3. State one application of chromatography. (1 mark)
16. Describe how the pH of a soil sample is determined.(2 marks)
17. Metal X, atomic number 11, burns in chlorine atomic number 17, to produce a white solid compound Y.(2 marks)
    1. Draw a dot (.) and cross (X) diagram to show bonding in compound Y.
    2. State one use of solid compound Y.(1 mark)
18. When a candle burns, the wax melts and after some time, the molten wax solidifies.
    1. State the type of change described. (1 mark)
    2. Give two characteristics of the change in (a). (1 mark)
19. Table 2 shows atomic numbers of elements C, D, E and F. The letters do not represent the actual symbols of the elements. Study it and answer the questions that follow.
    Table 2
    

    Element	Atomic Number
    C	17
    D	10
    E	11
    F	12

    1. Select:
       1. the least reactive element. Explain. (2 marks)
       2. an element that react vigorously with water.  (1 mark)
    2. Write an equation for the reaction between element and water. (1 mark)
20.                          
    1. Study the following equation and answer the questions that follow.
       Cuo(s) + H₂(g)→ Cu(s) + H₂O(l)
       1. Identify the substance which is oxidised in the equation. (1 mark)
       2. State the property of hydrogen shown in the equation. (1 mark)
    2. State how the purity of water is tested. (1 mark)
21. The diagram in figure 4 is part of a set up used by a student to prepare and collect oxygen gas.
    
    Figure 4
    1.                        
       1. Complete the set up in figure 4.(2 marks)
       2. Identify liquid Y. (1 mark)
       3. State one use of oxygen. (1 mark)

SECTION C: PHYSICS (33 marks)
Answer all the questions in this Section in the spaces provided.

22. State one branch of Physics.(1 mark)
23. The volume of a piece of metal is 7.5 cm³. Given that its mass is 85.5g, determine its density.(3 marks)
24. Figure 5 shows a capillary tube dipped into a beaker half full of water.
    
    Figure 5
    Explain why the level of water in the capillary tube is higher than the level in the beaker(2 marks)
25. Figure 6 shows a can full of water. Three holes A, B and C on the side of the can are sealed with plasticine.
    
    Figure 6
    1. On the figure, sketch the paths of water as it flows from the holes A, B and C when the plasticine is removed.
       (1 mark)
    2. Explain the answer in (a)(2 marks)
26. Distinguish between the solid and liquid states of matter with reference to the spacing and movement of the molecules.(2 marks)
27. A spring of length 10cm is stretched by a force of 5 N. Determine the spring constant.(3 marks)
28. A fruit on a tree has potential energy. State the energy changes that take place when the fruit falls to the ground.(2 marks)
29. Figure 7 shows two stone blocks A and B of same base area resting on a horizontal surface.
    
    Figure 7
    State with a reason the block which is more stable.(2 marks)
30. State two features in the construction of a steel bridge that allow for expansion. (2 marks)
31. Figure 8 shows a velocity-time graph of the motion of a car.
    
    Figure 8
    Explain the motion of the car in sections.
    1. AB(1 mark)
    2. BC (1 mark)
    3. CD (1 mark)
32. A moment of 12 Nm is required to open a door of width 100cm. Determine the minimum force required to open the door.(3 marks)
33. What feature in a vacuum flask minimises heat loss by:
    1. Convection (1 mark)
    2. Conduction (1 mark) 
    3. Radiation (1 mark)
34. State two ways in which friction between two bodies can be reduced.(2 marks)
35. A log of wood of weight 200N floats on water. Determine the mass of the water displaced by the log. (Density of water is 1000 kgm^-3).(2 marks)

MARKING SCHEME

1.                                
   1.                          
      1. Fungi:
      2. Protoctista/Protista;
   2. To prevent accumulation of metabolic wastes to toxic levels/Ensures continuous removal of waste products to maintain a constant internal environment;
2.                          
   1.                      
      1. Synthesis of DNA, RNA and ribosomes;
      2. Packaging and secretion of glycoproteins/ secretion of synthesized proteins and carbohydrates and form lysosomes;
3. Mg = Length of image
            Length of object
   300,000 = 4 ;
                   x
   x =    4     = 0.00001333cm;
       300,000
4.                    
   1. The rod tilted downwards towards F;
   2. Potato cylinder at F was placed in hypotonic solution; (distilled water) and it gained water by osmosis; hence became heavier;
      OR
      Potato cylinder at E was placed in hypertonic solution; lost water by osmosis, and became lighter.
5.                                      
   1.                      
      1. All the type arrangement and number of teeth in a mammal;
      2. Is half the number of the type, position, number and arrangement of various types of teeth on the upper and lower jaws of mammals;
   2.                  
      1.                                    
         
      2. 2 = 4 = 10
         3    6
6.        
   1.                              
      1. Root;
      2. Monocotyledon;
      3. Vascular bundles arranged as a ring; and xylem alternates with phloem; presence of pith
   2. Absorption of water and mineral salts
7.                        
   1.                  
      • Balloons inflate 
      • Rubber sheet bulges downwards 
      • Volume of belt jar increases
      • Air rushes into the balloon 
   2. Diaphragm
8.                    
   1. Respiration/Aerobic respiration
   2. Respiratory enzymes
9.                    
   • Erector pili muscles contract and body hair stands to trap a layer of air for insulation against heat loss;
   • Vasoconstriction to direct blood vessels into a shunt to minimize heat loss,
   • Increased rate of metabolic activities to generate metabolic heat;
   • Shivering due to involuntary contraction of the skeletal muscles to generate heat.
10.              
    • Tannins
    • Caffeine
    • Quinine
    • Cocaine
    • Cannabis
    • Rubber
    • Colehiahe
    • Gum
    • Arabica
    • Papain
    • Khat
11.                        
    1.                
       1. Y
       2. (Marks re distributed to No. 18b)
       3. Z
    2. X and W
12.                      
    1.                        
       1. Copper (II) nitrate 
       2. Copper (II)oxide
    2. 2Cu(NO₃)_2(S) →2CuO(s) +4NO₂(g) +O₂(g).
13.                            
    1. The ions in Lead (II) Bromide solid are immobile and therefore unable to conduct an electric current.
    2. Heat the Lead (II) Bromide to make the ions mobile.
14.                            
    1. Ethanoic acid is a weak acid while hydrochloric acid is a strong acid. Hydrochloric acid completely ionizes in solution while Ethanoic acid is partly ionized in solution.
       Hydrochloric acid solution has a higher hydrogen concentration than Ethanoic acid.
    2. Water softening is the removal of Ca²⁺ and Mg²⁺ from hard water.
15.                                              
    1.                           
       
    2. B
    3.                  
       • In food industry
       • Separate and detect contaminants such as aflatoxins
       • Detecting traces of flammable chemicals in burned materials from possible arson sites. 
16.            
    1.                                              
       • Add water to the soil sample and shake to dissolve
       • Filter to remove insoluble particles and impurities.
       • Transfer about 5ml of the solution to a beaker and add universal indicator.
       • Compare its colour to the pH chart provided.
17.                      
    1.                            
       
18.                                  
19.                                      
20.                                      
21.                                        
22. Mechanics, Optics, Electricity, Magnetism, Waves, Atomic Physics, Thermodynamics
    (1 mark for any one correct branch of physics)
23. Density = √mass
                    volume
    = 85.5
        7.5
    =11.4gcm^-3
24. Adhesive forces between glass and water molecules are greater higher than cohesive forces between water molecules therefore adhesive forces V pull water up the capillary tube.
25.                    
    1.                                 
       
    2. - Pressure is greatest/highest/most at CV and therefore the jet is longest or Pressure is least/lowest at A and therefore the jet is shortest
       - Pressure increases with depth V.
26. Molecules in a solid are closely packed and are continuously vibrating about fixed positions while molecules in a liquid move freely/slide over each other in constant motion unlike those of a solid.
    The spacing/distance between the molecules of a solid is smaller than the spacing/distance between molecules of a liquid.
27. F = ke
    5 = ke
    k=5/e Ncm^-3 
28. PE......................√-KE............................. √SOUND/HEAT
29. B
    Since B has a lower centre of gravity
30. Expansion gaps and use of rollers.
31. AB - accelerating uniformly/constantly or velocity increasing uniformly with increase in time. 
    BC - moving with uniform velocity or zero acceleration
    CD - decelerating uniformly/constantly or velocity decreasing uniformly with increase in time. 
32. Moment of a force = Force X Perpendicular distance
    12 = F x 100
                 100
    F =12N
33.                    
    1. Vacuum between glass walls/cork/lid/plastic top/covery 
    2. Glass walls/cork/vacuum between walls 
    3. Silvering/shinny polishing the inside walls
34. - By oiling/greasing/use of lubricant
    - By using rollers/ball bearings
    - By polishing/smoothening the surfaces in contact (Any two)
35. Weight of water displaced = weight of log√
    = mg
     m = 200
             10    
    = 20 kg