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

QUESTIONS

1. State two branches of chemistry (2MKS)
2. Define each of the following terms (2MKS) 
   1. Matter
   2. Conductor
3. Differentiate between a pure substance and a mixture (2Mks)
4. State two factors that determine the choice of the method of separation of mixtures (2mks)
5. Describe how you can separate a mixture of iodine, salt and sand (3mks)
6. State the use of each of the following laboratory apparatus (3MKS)
   1. Pipette
   2. Deflagrating spoon
   3. Thistle funnel
7. James a form one student wants to measure accurate volume of a solution in the laboratory State TWO apparatus that James could use (2MKS)
8.                      
   1. Name two laboratory apparatus that can be made of glass  (2MKS)
   2. State two advantages of apparatus made of glass in chemistry experiments    (2MKS)
9.                        
   1. Draw and name the regions of a luminous flame (3mks)
   2. A wooden splint was slipped through a region of a particular flame in the laboratory and was burnt as shown in the diagram below
      
      
      1. Name the type of flame the splint was slipped through (1mk)
      2. Stating the region explain why the splint was burnt the way it is shown in the diagram (2mks)
      3. State one disadvantage of using the above type of flame in the laboratory (1mk)
10.                      
    1. Define the term crystallization (1mk)
    2. State two applications of crystallization (2mks)
11.                        
    1. What is solvent extraction (1mk)
    2. Describe how oil is extracted from ground nut seeds (3mks)
12. For each of the following, state the type of change observed (4mks)
    1. Melting and cooling candle wax
    2. Heating and cooling zinc oxide   
    3. Burning magnesium in air 
    4. Heating hydrated copper (ii) sulphate 
13. Study the diagram below and answer the questions that follow (5mks)
    
    
    1. Name each of the parts X and Y
    2. What is the name given to the method used above for the separation of mixture P?
    3. State two industrial applications of the method mentioned above
    4. Suppose the mixture P was paraffin and water, which apparatus could have been used to separate them?
14. State the effect of impurities on (2mks)
    1. Melting point
    2. Boiling point
15. The diagram below shows the heating curve of pure water On the same diagram, sketch the graph if water containing impurities was used    (1mks)
    
16.                                
    1. State the kinetic theory of matter (1mk)
    2. By use of a clear (theoretical model) diagram, explain the nature of particles in the three states of matter (3mks) 

MARKING SCHEME

1. State two branches of chemistry (2MKS)
   • organic chemistry 
   • analytical chemistry
   • inorganic chemistry
   • biochemistry
2. Define each of the following terms (2MKS) 
   1. Matter
      • anything that has mass and occupies space
   2. Conductor
      • substance which allow electrical energy to flow through them
3. Differentiate between a pure substance and a mixture (2Mks)
   • a pure substance contains only one kind of particle or fixed chemical composition while a mixture is a substance made up of two or more substances combined
4. State two factors that determine the choice of the method of separation of mixtures (2mks)
   • density of the particles forming the mixture
   • the solubility of the particles forming the mixture
   • magnetism
   • boiling point
5. Describe how you can separate a mixture of iodine, salt and sand (3mks)
   • heat the mixture and condence the vapour produced to collect deposits of iodine
   • add water to the remaining mixture then stir for salt to dissolve
   • filter to obtain sand as residue then heat the filtrate to saturation to obtain salt crystals
6. State the use of each of the following laboratory apparatus (3MKS)
   1. Pipette
      • used to measure faily accurate volumes of liquids in the laboratory
   2. Deflagrating spoon
      • used for holding substances being burned in glass jars
   3. Thistle funnel
      • used for delivering liquid substances in reaction vessels
7. James a form one student wants to measure accurate volume of a solution in the laboratory State TWO apparatus that James could use (2MKS)
   • pipette 
   • burette
   • syringe
   • volumetric flask
8.                      
   1. Name two laboratory apparatus that can be made of glass  (2MKS)
      • conical flask
      • beaker
   2. State two advantages of apparatus made of glass in chemistry experiments    (2MKS)
      • easy to clean
      • can be used when heating substances
9.                        
   1. Draw and name the regions of a luminous flame (3mks)
      
   2. A wooden splint was slipped through a region of a particular flame in the laboratory and was burnt as shown in the diagram below
      
      
      1. Name the type of flame the splint was slipped through (1mk)
         • non-luminous flame
      2. Stating the region explain why the splint was burnt the way it is shown in the diagram (2mks)
         • the outter pale blue zone of th non luminous flame is the hottest region as compared to the inner regions
      3. State one disadvantage of using the above type of flame in the laboratory (1mk)
         • it is not easily visible hence accidents are easy to make
10.                      
    1. Define the term crystallization (1mk)
       • the process of obtaining crytsals from a saturated solution
    2. State two applications of crystallization (2mks)
       • extraction of salt from salty water
       • extraction of medical substances from plants
11.                        
    1. What is solvent extraction (1mk)
       • the process of removing a substance from a solution or mixture by dissolving it in another
    2. Describe how oil is extracted from ground nut seeds (3mks)
       • crush the ground nut seeds then add propane. The dissolves in propane . remove the solid part then put the resulting solution in the sun. The propane evaporates leaving the oil.
12. For each of the following, state the type of change observed (4mks)
    1. Melting and cooling candle wax - temporary physical change
    2. Heating and cooling zinc oxide  - temporary physical change
    3. Burning magnesium in air - temporary chemical change
    4. Heating hydrated copper (ii) sulphate - temporary chemical change
13. Study the diagram below and answer the questions that follow (5mks)
    
    
    1. Name each of the parts X and Y
       • x - fructionating column
       • y - liebig condenser
    2. What is the name given to the method used above for the separation of mixture P?
       • fractional distillation
    3. State two industrial applications of the method mentioned above
       • in manufacture of nitrogen and oxygen
       • separating the component of crude oil
    4. Suppose the mixture P was paraffin and water, which apparatus could have been used to separate them?
       • separating funnel
14. State the effect of impurities on (2mks)
    1. Melting point
       • lowers the melting point
    2. Boiling point
       • raises the boiling point
15. The diagram below shows the heating curve of pure water On the same diagram, sketch the graph if water containing impurities was used    (1mks)
    
16.                                
    1. State the kinetic theory of matter (1mk)
       • matter is made up of small particles that are in continuous state of random motion
    2. By use of a clear (theoretical model) diagram, explain the nature of particles in the three states of matter (3mks)