1Bring out the difference between a word equation and a formula equation.
2Bring out the difference between reactants and products.
3Give the reason: products are different from reactants.
4What is a chemical reaction?
5What is a chemical equation?
6How can a formula equation be balanced? Write with an example.
7Express the given chemical reaction as a balanced formula equation: magnesium oxide + hydrogen → magnesium + water
8Express the given chemical reaction as a balanced formula equation: calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide
9Express the given chemical reaction as a balanced formula equation: potassium + chlorine → potassium chloride
10Express the given chemical reaction as a balanced formula equation: sodium + oxygen → sodium oxide
11Express the given chemical reaction as a balanced formula equation: hydrogen + oxygen → water
12The reaction between zinc and hydrochloric acid is \( \mathrm{Zn} + 2\mathrm{HCl} \rightarrow \mathrm{ZnCl}_2 + \mathrm{H}_2 \). What reaction takes place if sulphuric acid is used in place of hydrochloric acid? Write the chemical equation.
13Write three points of difference between a physical change and a chemical change.
14What does the arrow in a chemical equation stand for, and why does it point from left to right?
15Why must a number inside a formula never be changed while balancing? Give one example.
16Count the atoms on both sides of \( \mathrm{N}_2 + 3\mathrm{H}_2 \rightarrow 2\mathrm{NH}_3 \) and show that it is balanced.