Chemistry Questions and Answers - Form 1 End Term 1 2021

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CHEMISTRY
FORM 1
END TERM EXAM
TERM 1 2021

INSTRUCTIONS

  • Answer all the questions
  1.      
    1. Define the term chemistry.1mk
    2. State three importance of studying chemistry.3mks
  2. The diagram below shows the relationship between the physical state of matter .study it and answer the questions that follows.
    chemf1et121q2
    1. Identify the processes R,V,W and U. 2mk
    2. Name two substances which under the process represented by S and T.2mks
  3. Draw and name the apparatus you would use in the separation of a mixture of kerosene and water. 2mks
  4. The curve below represents the variation of temperature with time when pure and impure samples of solid were heated separately
    chemf1et121q4
    Which curve shows the variation of temperature for the pure solids? Explain 2mks
  5.    
    1. State the effect of an impurity on the melting and boiling point of a pure substance. 2mks
    2. State four differences between temporary physical change and temporally chemical change. 4mks
  6. The diagram below shows a Bunsen burner in use.
    chemf1et121q6
    1. Name the regions labeled D, C, and E. 3mks
    2. Identify the hottest part of the flame.1mk
  7. Differentiate the following terms.
    1. Drug abuse and prescription.2mkS
    2. Conductors and non –conductors.2mks
  8. The diagram below represents the apparatus that may be used to separate a mixture of two miscible liquids C and D whose boiling points are 80ºC and 110ºC
    chemf1et121q8
    1. Name A and B 2mks
    2. What is the purpose of the thermometer? 1mk
    3. Which liquid was collected first? Explain. 2mks
  9. The set up below represent the apparatus that may be used to separate ethanol from water.
    chemf1et121q9
    1. Why is it possible to separate ethanol from water.2mks?
    2. Explain the role played by the fractionating column.2mks
    3. State the role of the glass beads in the fractionating column.1mk
    4. At what temperature does ethanol distill off.1mk?
    5. What would happen if the inlet and outlet were exchanged in the Liebig’s condenser .2mks?
  10. Define the following terms .3mks
    1. Atom
    2. Molecule
    3. Compound
  11. Fill the following table 3mks
    Element Latin name Symbol
    Potassium    K
       Natrium  
     silver  Argentums  
      Aurum   
  12.      
    1. Name the suitable solvent for extracting an indicator from flowers.1mk
    2. Give a reason why solvent named in A above is used.1mk
  13. Explain the differences between solid, liquid , and gaseous state using theoretical model of matter in terms of kinetic theory.6mks
  14. The graph below shows the shape of the curve obtained by a student when solid X was heated to boiling determine the melting point of solid X .1mk
    chemf1et121q14
    State and explain what proportion PQ, QR and RS represent.6mks
  15. Spots of pure pigment A and B and a mixture Z were placed on a filter paper and allowed to dry. The paper was then dipped in a solvent and results obtained as follows on a paper chromatogram.
    chemf1et121q15
    1. Which is the
      1. Baseline1mk
      2. Solvent front.1mk
    2. Which of the pure pigment was component of Z . explain.2mks
    3. Name a solvent that is suitable in paper chromatography.1mk
  16. State two apparatus used as a source of heat in a laboratory.2mks
  17. State the function of the following apparatus in the laboratory. 2mks
    1. Deflagrating spoon
    2. Desiccators


MARKING SCHEME

    1. Define the term chemistry.1mk
      • It is the study of the structure properties and composition of matter and changes matter undergoes

    2. State three importance of studying chemistry.3mks
      • Food production to fight hunger
      • Manufacture drugs to fight diseases
      • Production of fuels for transport and domestic use
      • Manufacture detergents

  1. The diagram below shows the relationship between the physical state of matter .study it and answer the questions that follows.
    chemf1et121q2
    1. Identify the processes R,V,W and U. 2mk
      • R- Melting
      • V- Evaporation
      • U- Freezing
      • W- Condensation

    2. Name two substances which under the process represented by S and T.2mks
      • Aluminium chloride
      • Benzoic acid
      • Iron(iii) chloride
      • Solid Carbon(iv) oxide

  2. Draw and name the apparatus you would use in the separation of a mixture of kerosene and water. 2mks
    chemf1et121qa3
  3. The curve below represents the variation of temperature with time when pure and impure samples of solid were heated separately
    chemf1et121q4
    Which curve shows the variation of temperature for the pure solids? Explain 2mks
    • II- Because it has a sharp boiling point

  4.    
    1. State the effect of an impurity on the melting and boiling point of a pure substance. 2mks
      • Impurity lowers the melting point of a substance while it raises the boiling point of a substance

    2. State four differences between temporary physical change and temporally chemical change. 4mks
      Temporary physical temporary chemical
      They are easily reversible They are irreversible
      No new substance is formed New substance is formed
      Mass of the substance does not change Change is accompanied by change in mass
      Are not accompanied by net heat change Heat energy is absorbed/ released
  5. The diagram below shows a Bunsen burner in use.
    chemf1et121q6
    1. Name the regions labeled D, C, and E. 3mks
      • D- Pale blue zone
      • C- Green blue zone
      • E- Almost colourless zone

    2. Identify the hottest part of the flame.1mk
      • Outer most region- pale blue region

  6. Differentiate the following terms.
    1. Drug abuse and prescription.2mks
      • Drug abuse is the use of a drug for a purpose not meant for it, prescription is a written instruction by a qualified medical officer

    2. Conductors and non –conductors.2mks
      • Conductors are substances which allows electrical energy to flow while non- conductors do not allow electricity to flow through them

  7. The diagram below represents the apparatus that may be used to separate a mixture of two miscible liquids C and D whose boiling points are 80ºC and 110ºC
    chemf1et121q8
    1. Name A and B 2mks
      • A- Distillate
      • B- Leibig condenser

    2. What is the purpose of the thermometer? 1mk
      • It is used to measure the temperature of the mixture

    3. Which liquid was collected first? Explain. 2mks
      • Liquid C is collected first because it has a lower boiling point

  8. The set up below represent the apparatus that may be used to separate ethanol from water.
    chemf1et121q9
    1. Why is it possible to separate ethanol from water.2mks?
      • It is because they have different boiling points

    2. Explain the role played by the fractionating column.2mks
      • It allows water vapour to condense into liquid and flow back into the flask before boiling point of water is reached

    3. State the role of the glass beads in the fractionating column.1mk
      • Glass beads increase the surface area for condensation

    4. At what temperature does ethanol distill off.1mk?
      • It distills off at 78°C

    5. What would happen if the inlet and outlet were exchanged in the Liebig’s condenser .2mks?
      • Condensation would still take place but it will be less efficient

  9. Define the following terms .3mks
    1. Atom
      • It is  the smallest particle of an element, which can take part in a chemical change

    2. Molecule
      • It is the smallest particle of an element or compound which can exist separately

    3. Compound
      • It is a pure substance made up of two or more elements chemically combined

  10. Fill the following table 3mks
    Element Latin name Symbol
    Potassium Kalium   K
    Sodium   Natrium Na 
     silver  Argentums Ag 
    Gold  Aurum   Au
  11.      
    1. Name the suitable solvent for extracting an indicator from flowers.1mk
      • Propanone

    2. Give a reason why solvent named in A above is used.1mk
      • It is able to dissolve components in a  flower

  12. Explain the differences between solid, liquid , and gaseous state using theoretical model of matter in terms of kinetic theory.6mks
    • In solids, particles are closely packed together
    • in liquids, particles are not closely parked together and move within the liquid container
    • In gases particles are widely separately and move independently

  13. The graph below shows the shape of the curve obtained by a student when solid X was heated to boiling determine the melting point of solid X .1mk
    chemf1et121q14
    1. Determine the melting point of Solid X(1mk)
      • QR
    2. State and explain what proportion PQ, QR and RS represent.6mks
      • PQ- Increase of temperature towards melting point. The solid X continuously absorbs heat energy in this region as it heads towards it's melting point.
      • QR- melting point. Solid x has reached its melting point and therefore the heat energy absorbed is contant in this region.
      • RS- increase of temperature to boiling point. After melting, X continuously absorbs more heat energy as it heads towards its boiling point

  14. Spots of pure pigment A and B and a mixture Z were placed on a filter paper and allowed to dry. The paper was then dipped in a solvent and results obtained as follows on a paper chromatogram.
    chemf1et121q15
    1. Which is the
      1. Baseline1mk
        • D

      2. Solvent front.1mk
        • C
    2. Which of the pure pigment was component of Z . explain.2mks
      • It is at the same point in the paper chromatograph as component Z

    3. Name a solvent that is suitable in paper chromatography.1mk
      • Propanone

  15. State two apparatus used as a source of heat in a laboratory.2mks
    • Bunsen burner
    • Spirit lamp
    • Candle

  16. State the function of the following apparatus in the laboratory. 2mks
    1. Deflagrating spoon - Used for holding substance being burned
    2. Desiccators - Used for drying or keeping substances free from moisture
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