Which decision should be made if the results of an experiment do not support the stated hypothesis? A To use the results as an idea for further testing. B To ignore the results and set a new experiment. C To repeat the experiment in the same way. D To identify a new problem.

(b) Answer the given questions by writing the correct answer in the blank spaces provided. (i) In which stage is the hypothesis tested during scientific investigation? ……………………. (ii) On which factor does the physical state of a molecule depend? ……………………. (iii) Which properties depend on the proportions of mixing substances in a mixture? ……………………. (iv) What are the building blocks of matter? ……………………. (v) Which particles are transferred during chemical reactions? …………………….

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(b) Differentiate luminous from non-luminous flame by giving five points. S/N Luminous flame Non luminous flame (i) (ii) (iii) (iv) (v)

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(b) Classify each of the following elements into their respective groups and periods. S/N Element Group Period (i) Calcium (ii) Hydrogen (iii) Chlorine (iv) Boron (v) Aluminium

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Categorize the three factors (variables) which affect the problem being investigated during scientific investigation.

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A mass of 20.0 g of petrol was burnt in air. The heat produced was used to heat 2.5 litres of water. Given that the heat value of petrol is 43,640 kJ/kg, by how much the temperature of water could have changed? (The specific heat capacity of water = 4.18 kJ kg-1 K-1, Density of water = 1000 kg/m3).

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Consider the reaction: 2H₂ + O₂ → 2H₂O. Calculate the number of moles of water produced when 4 moles of hydrogen react completely with oxygen.

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(a) Giving a reason, state whether rust will form or not in each of the situations (i) - (vi). (i) Iron bar is dipped into boiling water. (ii) Painted iron is dipped into un-boiled water. (iii) Iron bar is dipped in un-boiled water. (iv) Oiled bar is left outside the room over nights. (v) Aluminium wire is dipped in un-boiled water. (vi) A dry iron bar is wrapped with cotton wool. (b) Briefly explain any four methods of preventing rusting. (i) (ii) (iii) (iv)

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