Page 102 - Innovator's Science-8

• Filter it and observe its colour.
• Leave this colourless solu on in a petri dish for a few hours.
• Keep s rring the solu on at regular intervals.
• What do you observe?
Lime
water
Petri Can you explain why the solution has turned milky? You know that lime
dish
water turns milky when carbon dioxide reacts with calcium hydroxide to
form calcium carbonate (insoluble tiny white particles) and water. Since
Lime water
turns milky lime water turns milky when exposed to air, this activity demonstrates the
Petri dish
presence of carbon dioxide in the air.
Lime water turns Calcium hydroxide + Carbon dioxide Calcium carbonate + Water
milky in the presence of
carbon dioxide Apart from gases, have you ever observed anything else present in the air?

Have you ever noticed tiny shining particles moving in a beam of sunlight
entering a dark room through a small opening? What are these particles?

Activity-2 Aim: To observe the presence of dust par cles suspended in
air.
Experiential Learning
If you take a clean black sheet of paper and leave it near an
open window or in a garden for a few hours, you'll no ce
Science ny par cles se ling on it. These small bits of dust come
Bytes
from the air around us. Even though we can't always see

Observation them, dust par cles float in the air and eventually land on
As air is a mixture, it surfaces. Using a magnifying glass helps you see them more
might also mix pollutants clearly. This simple ac vity shows that dust is present in the
with it. Major pollutants air, but it's not actually part of the air itself—it's a pollutant.
include par culate ma er
Black sheet of paper
(dust, soot) and gases The amount and type of dust in the air can change (a) with no dust particles;
such as carbon monoxide, depending on the loca on and me.
(b) with dust particles
nitrogen oxides, sulphur
dioxide and ozone. To TYPES OF MIXTURES
describe how clean or
polluted the air is, we use You know that the term 'mixture' in common usage refers to the mixing of
an index called the Air two or more components. The components of a mixture may themselves
Quality Index (AQI).
be mixtures, as in poha and sprout salad, or pure substances like sugar or
common salt dissolved in water. However, in science, all the components of
a mixture must be pure substances only.
Different types of Mixtures

Uniform or
S.No. Mixture-type Examples
non-uniform
1. Gas and gas Air Uniform
2. Gas and liquid Aerated water (soda water) ______________
Oxygen dissolved in water ______________
Poha
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