Page 61 - Chemistry ICSE Class IX

Chemical Changes and Reactions 49

ƒ dŽ ƉƌĞǀĞŶƚ ƚŚĞ ĞƐĐĂƉĞ ŽĨ ĮŶĞ ƉĂƌƟĐůĞƐ ŽĨ ŵĂŐŶĞƐŝƵŵ ŽdžŝĚĞ͕ ƉůĂĐĞ Ă ůŝĚ ŽǀĞƌ ƚŚĞ ĐƌƵĐŝďůĞ͘
ƒ tŚĞŶ Ăůů ƚŚĞ ŵĂŐŶĞƐŝƵŵ ŝƐ ďƵƌŶƚ͕ ĐŽŽů ƚŚĞ ĐƌƵĐŝďůĞ ĂŶĚ ŝƚƐ ĐŽŶƚĞŶƚƐ ŝŶ Ă ĚĞƐŝĐĐĂƚŽƌ͘ dŚĞ ǁŚŝƚĞ ƐƵďƐƚĂŶĐĞ ŝŶ ƚŚĞ
ĐƌƵĐŝďůĞ ŝƐ ŵĂŐŶĞƐŝƵŵ ŽdžŝĚĞ ;DŐKͿ͘
ƒ tĞŝŐŚ ƚŚĞ ĐƌƵĐŝďůĞ ĂůŽŶŐ ǁŝƚŚ ƚŚĞ ƉƌŽĚƵĐƚ ;ŵĂŐŶĞƐŝƵŵ ŽdžŝĚĞͿ͘ ZĞĐŽƌĚ ƚŚŝƐ ŵĂƐƐ ĂůƐŽ͘
OďserǀaƟons:
DĂƐƐ ŽĨ ĞŵƉƚLJ ĐƌƵĐŝďůĞ н DĂŐŶĞƐŝƵŵ ƌŝďďŽŶ с m Ő
ϭ
DĂƐƐ ŽĨ ĐƌƵĐŝďůĞ н DĂŐŶĞƐŝƵŵ ŽdžŝĚĞ с m Ő
Ϯ
Conclusion: ^ŝŶĐĞ m ŝƐ ŐƌĞĂƚĞƌ ƚŚĂŶ m ƚŚĞ ŵĂƐƐ ŽĨ ŵĂŐŶĞƐŝƵŵ ĂŌĞƌ ďƵƌŶŝŶŐ ŝƐ ŵŽƌĞ ƚŚĂŶ ƚŚĞ ŵĂƐƐ ŽĨ ŵĂŐŶĞƐŝƵŵ ƚĂŬĞŶ͘
ϭ
Ϯ
ExplanaƟon: DĂŐŶĞƐŝƵŵ ŽŶ ďƵƌŶŝŶŐ ŝŶ Ăŝƌ ĨŽƌŵƐ ŵĂŐŶĞƐŝƵŵ ŽdžŝĚĞ͘ /ƚ ŐĂŝŶƐ ŵĂƐƐ ďLJ ĐŽŵďŝŶŝŶŐ ǁŝƚŚ ƚŚĞ ƌĞƋƵŝƌĞĚ ĂŵŽƵŶƚ
ŽĨ ŽdžLJŐĞŶ ĨƌŽŵ ƚŚĞ Ăŝƌ͘
ďƵƌŶ
ϮDŐ;sͿ н K ;gͿ o ϮDŐK;sͿ
Ϯ
ACTIVITY 5 Aim: dŽ ƐŚŽǁ ƚŚĂƚ ƚŚĞ ďƵƌŶŝŶŐ ŽĨ Ă ĐĂŶĚůĞ ŝŶǀŽůǀĞƐ Ă ŐĂŝŶ ŝŶ ƚŽƚĂů ŵĂƐƐ
Materials required: ĂŶĚůĞ͕ ĨƵŶŶĞů͕ ĚĞůŝǀĞƌLJ ƚƵďĞ͕ ŐůĂƐƐ ƚƵďĞ ǁŝƚŚ Ă ĐŽƌŬ ŚĂǀŝŶŐ ƚǁŽ ďŽƌĞƐ͕ ĞƚĐ͘
Procedure: &ŽůůŽǁ ƚŚĞ ƐƚĞƉƐ ŐŝǀĞŶ ďĞůŽǁ͗

ƒ dĂŬĞ Ă ǁŝĚĞ ŐůĂƐƐ ƚƵďĞ ;Žƌ ŐůĂƐƐ ĐŚŝŵŶĞLJͿ͘
ƒ WĂĐŬ Ăƚ ŽŶĞ ŽĨ ŝƚƐ ĞŶĚƐ ;ƚŚĞ ƵƉƉĞƌ ĞŶĚͿ͕ ůĂLJĞƌƐ ŽĨ ƐŽĚĂůŝŵĞ͕ ĨƵƐĞĚ ĐĂůĐŝƵŵ ĐŚůŽƌŝĚĞ ďĞƚǁĞĞŶ ǁŝƌĞ ŐĂƵŐĞƐ ĂŶĚ ĐŽƩŽŶ

ǁŽŽů ƐĞƉĂƌĂƟŽŶƐ͘
ͻ &ƵƐĞĚ ĐĂůĐŝƵŵ ĐŚůŽƌŝĚĞ ĂďƐŽƌďƐ ŵŽŝƐƚƵƌĞ͘
ͻ ŽƩŽŶ ǁŽŽů ĂƌƌĞƐƚƐ ƚŚĞ ƵŶďƵƌŶƚ ĐĂƌďŽŶ ƉĂƌƟĐůĞƐ͘
ͻ ^ŽĚĂůŝŵĞ ĂďƐŽƌďƐ ĐĂƌďŽŶ ĚŝŽdžŝĚĞ͘
ƒ WůĂĐĞ Ă ĐĂŶĚůĞ ŽŶ Ă ĐŽƌŬ ǁŝƚŚ ƚǁŽ ŚŽůĞƐ Ăƚ ƚŚĞ ďŽƩŽŵ ŽĨ ƚŚĞ ŐůĂƐƐ ƚƵďĞ͘
ƒ ^ƵƐƉĞŶĚ ƚŚĞ ǁŚŽůĞ ĂƉƉĂƌĂƚƵƐ ĨƌŽŵ ƚŚĞ ďĞĂŵ ŽĨ Ă ďĂůĂŶĐĞ ĂŶĚ ǁĞŝŐŚ ŝƚ͘
ƒ ZĞĐŽƌĚ ŝƚƐ ŵĂƐƐ ŝŶ LJŽƵƌ ŶŽƚĞŬ͘
ƒ >ŝŐŚƚ ƚŚĞ ĐĂŶĚůĞ ĂŶĚ Įƚ ƚŚĞ ĐŽƌŬ ŝŶƚŽ ƚŚĞ ůŽǁĞƌ ĞŶĚ ŽĨ ƚŚĞ ƚƵďĞ͘
ƒ ůůŽǁ ƚŚĞ ĐĂŶĚůĞ ƚŽ ďƵƌŶ ĨŽƌ ƐŽŵĞ ƟŵĞ͕ ĂŶĚ ĂŐĂŝŶ ŶŽƚĞ ĚŽǁŶ ƚŚĞ ŵĂƐƐ ŽĨ ƚŚĞ ƐĞƚͲƵƉ͘
OďserǀaƟons: /ŶŝƟĂů ŵĂƐƐ ŽĨ ƚŚĞ ƐĞƚͲƵƉ с m Ő
ϭ
&ŝŶĂů ŵĂƐƐ ŽĨ ƚŚĞ ƐĞƚͲƵƉ с m Ő
Ϯ
dŚĞ ŵĂƐƐ m Ő ŝƐ ŐƌĞĂƚĞƌ ƚŚĂŶ ƚŚĞ ŵĂƐƐ m Ő͘
Ϯ ϭ
Conclusion: dŚĞ ƌĞƐƵůƚƐ ƐŚŽǁ ƚŚĂƚ ďƵƌŶŝŶŐ ŽĨ Ă ĐĂŶĚůĞ ƌĞƐƵůƚƐ ŝŶ Ă ŐĂŝŶ ŝŶ ƚŚĞ ƚŽƚĂů ŵĂƐƐ͘
How is the Balance of Carbon Dioxide and Oxygen

Maintained in Nature
Both oxygen and carbon dioxide gases are constantly being used up in
many natural processes. Yet their concentration in the atmosphere is nearly
constant at 20.9 per cent for oxygen and 0.03 per cent for carbon dioxide.
This occurs due to a balance between the consumption and production
of these gases on the earth.

Consumption and production of oxygen in nature

Oxygen (present in the air) is consumed by
ƒ the plants, animals and decomposers during respiration.
ƒ the fossil fuels during burning. Fig. 2.4 When a candle burns, there is
a gain in total mass of all the products
In both the processes, carbon dioxide (CO ) and water vapour (H O) and the left-over candle
2
2
are produced. These products escape into the atmosphere.
Oxygen is also used up by the sediments in the seas/oceans. dŚĞ ƉƌŽĐĞƐƐĞƐ ŽĨ ƉŚŽƚŽƐLJŶƚŚĞƐŝƐ͕
Oxygen is produced in nature when green plants make food from ƌĞƐƉŝƌĂƟŽŶ ĂŶĚ ďƵƌŶŝŶŐ ŽĨ ĨƵĞůƐ
carbon dioxide and water in the presence of sunlight by a process called ŵĂŝŶƚĂŝŶ ƚŚĞ oxygen-carbon
dioxide balance ŝŶ ŶĂƚƵƌĞ
photosynthesis. The released oxygen escapes into the atmosphere.