Chemistry Questions and Answers - Form 2 Term 1 Opener Exams 2023

INSTRUCTIONS TO CANDIDATES

• Write your name and admission number.
• Answer all the questions in the spaces provided after every question.
• All working for numerical questions must be clearly shown.

1.  
   1. A form one girl slipped a wooden splint at the innermost part of non-luminous flame as shown.
                
      
      1. Using a well labeled diagram, explain the observations made when the wooden splint is removed. (2mks)
   2. Name another type of flame produced by Bunsen burner. (1mk)
   3. State three differences between the two types of flames (3mks)
2.  
   1. What is drug abuse? (1mk)
   2. State two effects of drug abuse in the society
   3. What are over the counter drugs? State two such drugs (2mks)
3. State four safety precautions or safety rules in the laboratory to control accidents (4mks)
4. Four solutions A,B,C and D had their pH values measured and recorded as follows:
   

   Solution	PH Value
   A	8.5
   B	1.5
   C	6.0
   D	13.0

   1. Identify from the list the solution which is:
      1. Strong acid (1mk)
      2. Weak base (1mk)
      3. Strong base (1mk)
   2. Which solution can react readily with magnesium ribbon to produce hydrogen gas (1mk)
   3. Which solution could be the solution of lemon juice? (1mk)
5. State two advantages of non- luminous flame over the luminous flame (2mks)
6. The following set-up of three test tubes was used to investigate rusting of iron nails. Study it and answer the questions that follows:
   
   1. State the set-up in which rusting did not occur. Explain (2mks)
   2. State one disadvantage of rusting (1mk)
   3. State two factors or conditions which accelerate rusting (2mks)
7. The following diagram shows the effects of heat on the physical states of substances
   
   1. Identify the processes represented by the letters A,B,C,D,E and F. (3mks)
   2. Name two substances that undergo the process labeled E and F (2mks)
   3. Name the best method that can be used to separate the following
      1. common salt from salt solution (1mk)
      2. paraffin from crude oil (1mk)
      3. iron filings in sulphur powder (1mk)
8. Describe two different experiments which can be used to show the presence of moisture in the atmosphere (4mks)
9. A student separated liquid P (Bpt= 78°C) and liquid Q (Bpt= 100°C) using the apparatus below
              
   1. Name the apparatus labeled (2mks)
      1. M –
      2. R –
   2. State one function of the glass beads in apparatus labeled R. (1mk)
   3. What is the reading on the thermometer when the first drops of the distillate appeared in the beaker (1mk)
   4. Which of the solutions remains in the flask? (1mk)
10.  
    1. What would be observed when the following substances are heated and cooled in a crucible
       1. Wax (1mk)
       2. Zinc oxide (1mk)
    2. Give the name for the type of change that takes place (1mk)
    3. State two characteristics of this type of change (2mks)
    4. State what is observed when copper (II) nitrate crystals are heated (2mks)
11. Complete the following table(4mks)
    

    Element	Symbol	Element	Symbol
    Silver			Cu
    	K	Mercury
    Sodium		Iron
    	Sn		Co

12. Write word equations for the following reactions between hydrochloric acid and the following
    1. Zinc (1mk)
    2. Magnesium oxide (1mk)
    3. Calcium carbonate (1mk)
13.  
    1. Candle wax is a compound consisting of two elements. Name the two elements (2mks)
    2. The set-up below was used to investigate the burning of a candle. Study it and answer the questions that follow:
               
       1.  What would happen to the candle if the pump was turned off? (2mks)
       2. State and explain the changes in mass that are likely to take place in tube N by the end of the experiment (2mks)
       3. Name two gases that comes out through tube M. (1mk)
       4. State two industrial uses of oxygen (2mks)
14. Study the graph on heat curves shown below
            
    1.  Which curve shows variation of temperature for a pure sample of solid? Explain (2mks)
    2. Explain in terms of kinetic energy what happens at the following regions during heating
       1. MN
       2. NO (3mks)
15. Study the diagram below used to prepare oxygen gas
            
    1. Name the apparatus labeled (2mks)
       1. W –
       2. X –
    2. Name solid A (1mk)
    3. Write a word equation for the reaction in the flask (2mks)
    4. State the test for oxygen gas (1mk)
16.  
    1. List down two sources of water (1mk)
    2. State three uses of water other than domestic use like cooking (3mks)
    3. List down three causes of water pollution (3mks)
17. Study the diagram below and use it to answer the question that follows:
    1. State the property of hydrogen gas tested in the experiment (1mk)
    2. State and explain what would happen to the copper(II) oxide in the experiment (2mks)
    3. Write word equation for the reaction in the combustion tube (2mks)
    4. State the test of hydrogen gas (1mk)
    5. State two uses of hydrogen gas (2mks)
18.  
    1. Define the term indicators as used in chemistry (1mk)
    2. Explain briefly how one can make simple flowers indicator in the laboratory (3mks)
19. A student was stung by bee in the laboratory. The laboratory technician used a certain solution X to wash the student. Name the solution X used to bring relief (1mk)
20. Sodium chloride (common salt) is contaminated with copper (II) oxide. Explain how pure sodium chloride can be obtained from the mixture (2mks)

MARKING SCHEME

1.  
   1.  
      
   2.  Luminous flame
   3.  
      

      Luminous flame	Non- luminous flame
      Yellow	Blue
      Not hot	Very hot
      Four zones	Three zones
      Quiet	Noisy/Roars

2.  
   1. Any usage of drug for a reason not intended for overdose of a type of a drug or under dose.
   2.  
      • Cause disease like liver cirrhosis/ cancer
      • Brings poverty in the society
      • Can cause marriage breakages
   3. Drugs which can be bought without doctor’s prescription instructions. Eg Actal, piriton, mara moja.
3.  
   • Label chemicals in use to avoid confusion
   • Clean benches after use
   • Wear shoes to avoid cut by broken glasses
   • Do not do practical without teacher assistant
   • Never hold hot test tubes with bare hands.
4.  
   1.  
      1. B
      2. A
      3. D
   2. B
   3. C
5.  
   • Its very hot
   • It does not produce soot so apparatus remains clean
6.  
   1. B or C – oil blocks oxygen entering the water. Boiled water has no oxygen
   2. Tear and wear of equipment or disfigures surfaces of equipment
   3. • Salty condition
      • Acidic condition
      • Basic condition
7.  
   1.  
      • A- melting
      • B – Freezing
      • C – Evaporating/ boiling
      • D- Condensation
      • E- Deposition/sublimation
      • F- Sublimation
   2.  
      1. Iodine NH₄Cl
      2. Benzoic acid Dry ice (solid CO₂ )
   3.  
      1. Evaporating/ simple distillation
      2. Fractional distillation
      3. Use magnet
8.  
   • Use anhydrous CuSO₄ which turns blue due to water which makes it hydrated.
   • Use anhydrous CoCl₂ which is blue and it will turn to pink to slow presence of water.
9.  
   1.  
      1. M – Liebig condenser
      2. R – Fractionating column
   2. Increase surface area for condensation
   3. 78°
   4. Q
10.  
    1.  
       1. Wax melts on heating. It turns back to solid wax on cooling.
       2. White zinc oxide changes to yellow zinc oxide on heating. On cooling the yellow solid turns to white ZnO.
    2. physical/Temporary change
    3.  
       • No change in mass
       • No new substance formed
       • Are reversible.
    4. Brown gas nitrogen (IV) oxide gas evolved, a colourless gas which rekindles a glowing splint formed and black solid of copper (II) oxide solid remains in the test tube.
11.  
    

    Element	Symbol	Element	Symbol
    Silver	Ag	Copper	Cu
    Potassium	K	Mercury	Hg
    Sodium	Na	Iron	Fe
    Tin	Sn	Cobalt	Co

12.  
    1. Zinc + hydrochloric → Zinc Chloride + hydrogen gas
    2. Magnesium oxide + hydrochloric acid →  magnesium chloride + water
    3. Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon (IV) oxide
13.  
    1. Carbon and hydrogen
    2.  
       1.  
          • It will go off. CO₂ gas formed accumulated and it does not support combustion
          • CO₂ gas formed does not support combustion
       2. Mass increases. Due to calcium oxide reacting with carbon (IV) oxide to form calcium carbonate.
       3. Rare gases eg Argon, Neon
       4.  
          • welding
          • Sea divers
          • Metal extraction
          • Mountain climbers
          • Stainless steel making
14.  
    1. curve I has sharp variation for boiling points or change of state
    2.  
       1. Solid absorbs heat energy. Kinetic energy of particles increases
       2. Heat absorbed is used to break the forces of attraction in the solid as it melts.
15.  
    1.  
       1. W – dropping funnel
       2. X – Bee- hive shelf
    2. Sodium peroxide
    3. Sodium peroxide + water → sodium hydroxide + oxygen gas
    4. Use glowing splint which rekindles
16.  
    1. Rivers, streams, oceans, lakes, dams
    2.  
       • Recreational – Boating, Swimming
       • In industries – cool engines
       • Agricultural (irrigation of plants)
       • Habitat for marine animals
    3.  
       • industrial effluents
       • Man’s activities bathing in water sources
       • Agricultural activities herbicides, pesticides
       • Sewage breakages/ leakages
17.  
    1. Reducing agent
    2.  
       • Black copper (II) oxide turns to brown
       • Reduction of the oxide takes place
    3. Copper (II) + hydrogen gas → copper + water
    4. Use a burning splint which gives a pop- sound
    5.  
       • Hardening oils to fat
       • Manufacture of HCl acid or ammonia gas
       • In rocket fuel
18.  
    1. Substance with one colour in alkalne solution and a different colour in acidic solution.
    2. Place flower petals in a crucible. Crush well and add little water. Continue to crush and add suitable solvent eg. Propanone filter and filtrate is required indicator
19. Any base/alkaline(NaOH) or potassium hydroxide .
20. Add water to the mixture and stir well. Filter to obtain copper (II) oxide as residue. Evaporate the filtrate to dryness to recover the sodium chloride crystals.