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

Boresha ili kuona majibu ya mfano.

(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.

Boresha ili kuona majibu ya mfano.

(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.

Boresha ili kuona majibu ya mfano.

(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.

Boresha ili kuona majibu ya mfano.

(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.

Boresha ili kuona majibu ya mfano.

(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.

Boresha ili kuona majibu ya mfano.

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

Boresha ili kuona majibu ya mfano.

(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.

Boresha ili kuona majibu ya mfano.