Chemistry Questions and Answers - Form 1 Mid Term 3 Exams 2023

INSTRUCTIONS

• ANSWER ALL THE QUESTIONS 

1. The pH scale has a range of values ranging from 0 to 14. On the pH scale, any substance with a pH value of 7 is neutral. Classify the following substances as either strong or weak acids or bases using their pH values. (4mks)
   1. pH 8
   2. pH 6
   3. pH1
   4. pH12
2. Grape juice is sour while aloe juice tastes bitter. What name is given to substances which taste (2mks)
   1. Sour
   2. Bitter
3. Complete the following word equation. (7mks)
   1. Acid + base → …………… + ……………………
   2. Acid + ……………….  →  salt + hydrogen gas
   3. Acid + Carbonate  → …………………..+ ……………… + water
   4. Acid + Hydrogen Carbonate →  salt + ……………………..+………………………
4. Study the table and answer the questions that follow. (3mks)
   

   Solution	Indicators
   	Colour in A	Colour in B	Colour in C
   Soap	Purple	Colourless	Orange
   Baking powder	Blue	Pink	Yellow
   Dilute hydrochloric acid	RED	Colourless	Pink
   Vinegar	Red	Colourless	Pink

   Identify the indicators A, B, and C
   1.  
   2.  
5. Use the diagram below to answer the questions that follow:
                                                        
   1. Name the process of separation above. (1mk)
   2. Name the parts labeled A and B. (2mks)
   3. Explain the role of glass beads. (1mk)
   4. Indicate the direction of flow of water in apparatus B. (2mks)
6. Matter may change from one state to another under sustain conditions. Study the illustration below and answer question that follow. (6mks)
                                                          
   Name process A to F
7. Consider the diagram below. (3mks)
                                                                             
   Name the parts indicated on the diagram which are represent as a,b,c,
   1. Unburned gas zone
   2. Pale blue zone
   3. Green blue zone
8. State any five laboratory safety rules. (5mks)
9.  
   1. The following table contains some elements. Study them and complete the table with correct chemical symbols. (5mks)
      

      Elements	Chemical symbol
      Sulphur
      Carbon
      Oxygen
      Hydrogen
      Nitrogen
      Magnesium
      Calcium
      Sodium
      Chlorine
      Copper

   2. The following table contains chemical symbols. Write down the name of the element represented by the symbol. (5mks)
      

      Chemical symbol	Name
      Pb
      Fe
      K
      Ag
      Hg

10. What is matter? (1mk)
11. Name the three states of matter (3mks)
12. The diagram below shows chromatograms for five different dyes.
                                                                  
    1. Name the technique used to separate the dyes. (1mk)
    2. What properties are required to separate the chromatograms in a dye? (1mk)
    3. On the diagram above label the solvent front by using a letter H. (1mk)
    4. Which letter represent baseline on the diagram. (1mk)
    5. Which dye is insoluble? (1mk)
    6. Which dye is pure? Explain (1mk)
    7. Which chromatogram is most soluble? (2mks)
13. Give five differences between non-permanent (physical) and permanent (chemical). (5mks)
    

    Non - permanent	Permanent

14.  
    1. Study the following table and classify the changes as non-permanent (physical) or permanent (chemical) after the action of heat. (2mks)
       

       	Substance	Original colour before   heating	Colour of residue after heating	Type of   change
       1	Copper ii Sulphate	Blue crystals	White powder (solid)
       2	Potassium	Purple	Black solid
       3	Zinc oxide	White (oxide)	Yellow when hot and white when cold
       4	Iodine	Black solid	Purple vapour when hot and black solid   when cold

       When water was added to the white Copper II Sulphate it turned to blue, explain the type of change. (1mk)
       1. What name is given to the blue copper II Sulphate? (1mk)
       2. White Copper II Sulphate. (1mk)
15. What is the confirmatory test for the presence of pure water? (1mk)
16. Define the following
    1. Mixture (1mk)
    2. Compound (1mk)
    3. Write a word equation when iron metal is heated together with Sulphur element to form iron II Sulphide. (1mk)
17. Name any four apparatus used to measure accurate volumes in the laboratory. (4mks)
18. Describe how you would separate a mixture of Iodine, salt and sand. (5mks)
19. Draw a well labeled diagram, how a mixture of oil and water can be separated. (4mks)

                                                                                      MARKING SCHEME

1. The pH scale has a range of values ranging from 0 to 14. On the pH scale, any substance with a pH value of 7 is neutral. Classify the following substances as either strong or weak acids or bases using their PH values. (4mks)
   1. PH 8
      • Weak base
   2. pH 6
      • Weak acid
   3. pH1
      • Strong acid
   4. pH12
      • Strong base
2. Grape juice is sour while aloe juice tastes bitter. What name is given to substances which taste (2mks)
   1. Sour
      • Acid
   2. Bitter
      • Base
3. Complete the following word equation. (7mks)
   1. Acid + base →  …salt………… + ……Water………………
   2. Acid + ……Metal……→……. salt + hydrogen gas
   3. Acid + Carbonate → ………Salt…………..+ …Carbon (IV) oxide……… + water
   4. Acid + Hydrogen Carbonate → salt + …Water…………………..+……Carbon (IV) Oxide
4. Study the table and answer the questions that follow. (3mks)
   

   Solution	Indicators
   	Colour in A	Colour in B	Colour in C
   Soap	Purple	Colourless	Orange
   Baking powder	Blue	Pink	Yellow
   Dilute hydrochloric acid	RED	Colourless	Pink
   Vinegar	Red	Colourless	Pink

   Identify the indicators A, B, and C
   1. Litmus
   2. Phenolphthalein
   3. Methyl orange
5. Use the diagram below to answer the questions that follow:
                                                                 
   1. Name the process of separation above. (1mk)
   2. Name the parts labeled A and B. (2mks)
      1. Fractionating column
      2. Leibig condenser6
   3. Explain the role of glass beads. (1mk)
      • Increases the surface area for effective condensation.
   4. Indicate the direction of flow of water in apparatus B. (2mks)
6. Matter may change from one state to another under sustain conditions. Study the illustration below and answer question that follow. (6mks)
                                                            
   Name process A to F
   1. Condensation/ Liquefaction
   2. Freezing/solidification
   3. Melting/fusion
   4. Evaporation/vaporisation
   5. Sublimation/deposition
   6. Sublimation
7. Consider the diagram below. (3mks)
                                                                                          
   Name the parts indicated on the diagram which represent.
   1. Unburned gas zone - Pale blue zone
   2. Pale blue zone  - green blue zone
   3. Green blue zone  - unburned gas
8. State any five laboratory safety rules. (5mks)
   • Never taste or eat anything in the laboratory to avoid poisoning.
   • Never smell gases directs
   • Label all the chemicals you are using to avoid confusion.
   • Always keep flammable substances away from flames because they easily catch fire.
   • If a chemical gets on your skin or in your mouth rise it immediately with a lot of clean water.
9.  
   1. The following table contains some elements. Study them and complete the table with correct symbols. (5mks)
      

      Elements	Chemical symbol
      Sulphur	S
      Carbon	C
      Oxygen	O
      Hydrogen	H
      Nitrogen	N
      Magnesium	Mg
      Calcium	Ca
      Sodium	Na
      Chlorine	Cl
      Copper	Cu

   2. The following table contains chemical symbols. Write down the name of the element represented by the symbol.
      

      Chemical symbol	Name
      Pb	Lead
      Fe	Iron
      K	Potassium
      Ag	Silver
      Hg	Mercury

10. What is matter? (1mk)
    • Is the study of the structure, properties and composition of matter and the changes that matter undergoes.
11. Name the three states of matter (3mks)
    • Solid
    • Liquid
    • Gases
12. The diagram below shows chromatograms for five different dyes.
                                                                   
    1. Name the technique used to separate the dyes. (1mk)
       • Chromatography
    2. What properties are required to separate the chromatograms in a dye? (1mk)
       • Different solubility/rates
       • Solubility in a given solvent.
       • Different densities.
    3.  On the diagram above label the solvent front by using a letter H. (1mk)
    4. Which letter represent baseline on the diagram. (1mk)
       • G
    5. Which dye is insoluble? (1mk)
       • B
    6. Which dye is pure? Explain (1mk)
       • C and A they have only one chromatogram.
    7. Which chromatogram is most soluble? (2mks)
       • E it moves furthest.
13. Give five differences between non-permanent (physical) and permanent (OS chemical). (5mks)
    1. Non- permanent
       • No new substance is formed
       • Reversible
       • No change in mass
       • No energy charge
       • Change is temporary or physical.
    2.  Permanent
       • New substance
       • Irreversible
       • Change in mass
       • Energy charge
       • Chemical change
14.  
    1. Study the following table and classify the changes as non-permanent (physical) or permanent (chemical) after the action of heat. (2mks)
       

       	Substance	Original colour before   heating	Colour of residue after heating	Type of   change
       1	Copper ii Sulphate	Blue crystals	White powder (solid)	Chemical
       2	Potassium	Purple	Black solid	Chemical
       3	Zinc oxide	White (oxide)	Yellow when hot and white when cold	Physical or non-   permanent
       4	Iodine	Black solid	Purple vapour when hot and black solid   when cold	Physical or non-   permanent

       When water was added to the white Copper II Sulphate it turned to blue, explain the type of change. (1mk)
       • Temporal chemical change.
         1. What name is given to the blue copper II Sulphate? (1mk)
            • Hydrous/hydrated
         2. White Copper II Sulphate. (1mk)
            • Anhydrous/an hydrated
15. What is the confirmatory test for the presence of pure water? (1mk)
    • Pure water boils at 100°C at sea level.
16. Define the following
    1. Mixture (1mk)
       • The elements (substances) in the mixture retains their chemical properties.
       • Two or more elements/substances physically combined and separated by physical means.
    2. Compound (1mk)
       • A pure substances made up of two or more elements chemically combined.
    3. Write a word equation when iron metal is heated together with Sulphur element to form iron II Sulphide. (1mk)
       • Iron + Sulphur iron II Sulphide.
17. Name any four apparatus used to measure accurate volumes in the laboratory. (4mks)
    • Volumetric flask
    • Burette
    • Pipette
    • Measuring cylinder
18. Describe how you would separate a mixture of Iodine, salt and sand. (5mks)
    • Heat to sublime Iodine.
    • Add water to dissolve salt.
    • Filter to obtain sand and salt solution.
    • Evaporate to obtain salt.
19. Draw a well labeled diagram, how a mixture of oil and water can be separated. (4mks)