Give an example of chemical changes in a reaction, where colour change is observed.

Give an example of chemical changes in a reaction involving

(i) formation of insoluble salt
(ii) formation of neutral products.

Give an example in chemical change of an exothermic and endothermic reaction involving carbon as one of the reactants.

What is meant by activity series of metals? Arrange the metals zinc, magnesium, aluminium, copper and iron in a decreasing order of reactivity?

(i) What will you observe when you put

(a) some zinc pieces into blue copper sulphate solution.
(b) Some copper pieces into green ferrous sulphate solution.

(ii) Write the balanced chemical equation also.

Ravi tested both the above liquids and found that these two differ in their odour as well as in inflammability. The former one is highly inflammable while the latter is used to extinguish fire. He predicts such a difference is due to difference in their 

Three beakers labelled as A, B and C each contains $25 \mathrm{ml}$ of water. A small amount of $\mathrm{NaOH}$, anhyd. ${\mathrm{CuSO}}_4$ and $\mathrm{NaCl}$ were added to the beakers A, B and C, respectively. It was observed that there was an increase in the temperature of the solutions of the beakers A and B whereas in case of beaker C, the temperature of the solution falls. Which one of the following statements is/are correct?

I. In beakers A and B exothermic process has occurred.

II. In beakers A and B, endothermic process has occurred.

III. In beaker C, exothermic process has occurred.

IV. In beaker C, endothermic process has occurred.

Consider the following equation for the process of photosynthesis, used by green plants to prepare their own food.

${\mathrm{xCO}}_2\left(\mathrm{y}\right)+ {\mathrm{zH}}_2\mathrm{O}\left(\mathrm{I}\right) \to {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{p}\right) + 6{\mathrm{O}}_2\left(\mathrm{aq}\right) + 6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{I}\right)$

Choose the correct words for $\mathrm{x}, \mathrm{y}, \mathrm{z}$ and $\mathrm{p}$.