Petrol is an example of:

The electronic configuration of silicon is:

(a) Define the term "element". (b) Name three elements found in the earth’s crust. (c) Classify the following as metals or non-metals: (i) Sodium (ii) Chlorine (iii) Carbon

1. Define the term "element". (2 mk)
2. Name three elements found in the earth’s crust. (3 mk)
3. Classify the following as metals or non-metals: (i) Sodium (ii) Chlorine (iii) Carbon (2 mk)

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(a) What is meant by the term "chemical bond"? (b) Draw diagrams to show the electron arrangement in: (i) A sodium atom (atomic number 11) (ii) A sodium ion (c) State the type of bond formed between sodium and chlorine.

1. Gas that relights a glowing splint (1 mk)
2. What is meant by the term "chemical bond"? (2 mk)
3. Draw diagrams to show the electron arrangement in: (i) A sodium atom (atomic number 11) (ii) A sodium ion (3 mk)
4. Process of coating iron with zinc (1 mk)
5. Separates immiscible liquids (1 mk)
6. State the type of bond formed between sodium and chlorine. (2 mk)
7. Element with atomic number 7 (1 mk)
8. Turns lime water cloudy (1 mk)
9. Used to measure precise volumes of liquids (1 mk)
10. Liquid at room temperature (1 mk)
11. Method to separate salt from seawater (1 mk)
12. Gas used in electric bulbs (1 mk)
13. Prevents direct heating of glassware (1 mk)

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(a) Define the term "mixture". (b) List three differences between a homogeneous and a heterogeneous mixture. (c) Name one method to separate sand from a sand-water mixture.

1. Define the term "mixture". (2 mk)
2. List three differences between a homogeneous and a heterogeneous mixture. (3 mk)
3. Name one method to separate sand from a sand-water mixture. (2 mk)

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(a) What is meant by the term "combustion"? (b) State three conditions necessary for combustion to occur. (c) Name one product formed when carbon undergoes combustion.

1. What is meant by the term "combustion"? (2 mk)
2. State three conditions necessary for combustion to occur. (3 mk)
3. Name one product formed when carbon undergoes combustion. (2 mk)

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(a) Define the term "oxidation number". (b) Calculate the oxidation number of the underlined elements: (i) K₂CO₃ (C underlined) (ii) HNO₃ (N underlined) (c) State one example of an oxidation reaction in everyday life.

1. Define the term "oxidation number". (2 mk)
2. Calculate the oxidation number of the underlined elements: (i) K₂CO₃ (C underlined) (ii) HNO₃ (N underlined) (3 mk)
3. State one example of an oxidation reaction in everyday life. (2 mk)

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(a) What is meant by the term "laboratory safety"? (b) List three safety rules to follow when handling acids in the laboratory. (c) Name one piece of equipment used for personal protection in the laboratory.

1. What is meant by the term "laboratory safety"? (2 mk)
2. List three safety rules to follow when handling acids in the laboratory. (3 mk)
3. Name one piece of equipment used for personal protection in the laboratory. (2 mk)

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(a) Define the term "fuel". (b) Name two fuels commonly used in Tanzanian households. (c) Explain one disadvantage of using firewood as a fuel.

1. Define the term "fuel". (2 mk)
2. Name two fuels commonly used in Tanzanian households. (3 mk)
3. Explain one disadvantage of using firewood as a fuel. (2 mk)

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(a) What is meant by the term "water purification"? (b) Describe two methods used to purify water in a laboratory. (c) State one importance of purifying water for domestic use.

1. What is meant by the term "water purification"? (2 mk)
2. Describe two methods used to purify water in a laboratory. (3 mk)
3. State one importance of purifying water for domestic use. (2 mk)

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