(a) A magnesium ribbon is taken and burnt. The ash is then dissolved in water. Name the various products formed. Support your answer with reactions.

(b) Burning of wood and cutting it into small pieces are considered as two different types of changes. Explain.
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Solution

(a) Products: 1 Mark
Equation: 1 Mark
(b) Explanation: 1 Mark

(a) When a magnesium ribbon is burnt, magnesium oxide is formed. The equation for the reaction is given below.
$M g + O_{2} \to M g O$

When magnesium oxide is dissolved in water, magnesium hydroxide is formed. The equation for the reaction is as follow:

$M g O + H_{2} O \to M g (O H)_{2}$

(b) When wood is burnt, a new substance is formed. Therefore, it is a chemical change. However, when we cut wood, only the shape and size of the wood changes but no new substance is formed. Therefore, it is a physical change.

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