Page 89 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

beyond a certain limit, even biological wastes destroy the harmony
of nature. Then you can imagine how worse would be the
situation caused by factory wastes. Hence, accumulation of those
materials, which cannot be biodegraded may become a threat
even to the existence of life itself.
For the sake of posterity, isn’t it the duty of each one of us to
protect the earth from getting polluted?

Hence there should be efforts to maximise the conversion of such
non-decomposable and polluting materials to environment
friendly materials. This should be one of the aims of studying
science.
Try to arrange a seminar on this topic.

Significant learning outcomes

The learner can
classify changes happening in nature into physical changes
and chemical changes.
classify chemical changes into thermochemical changes,
photochemical changes and electrochemical changes.
find examples for exothermic and endothermic reactions.

use electrochemical cells judiciously.
electroplate different objects.

engage in activities to prevent environmental pollution.

Let us assess

1. Assess the chemical reactions given below and answer the
questions.

Calcium carbonate + heat Calcium oxide +Carbon dioxide
Calcium oxide + water Calcium hydroxide + heat

a) Mention the reactants and products in each case.
b) Which among these is endothermic? Which one is
exothermic?

88 Basic Science VIII