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CHEMISTRY [3 Mark Question Answer]

Water · ICSE STD 8 (ICSE - English Medium). 3 questions.

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[3 Mark Question Answer]

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Question 13 Marks
How does the anomalous expansion of water help aquatic organisms in cold climates?
Answer
The anomalous expansion of water helps in the survival of water animals in very cold climates. Initially when the temperature of waterfalls, becomes heavier and sinks down. This process continues till $4^\circ C$. Then after this expansion takes place. The surface layer of water gets freezed. Ice being a bad conductor of heat does not allow loss of heat from the water below and results in the survival of water animals.
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Question 23 Marks
What is metal activity series ?
Answer
$[$The arrangement of metals in the decreasing order of their reactivity in the form of a series is called the activity or reactivity series of metals.$]$
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Question 33 Marks
Suggest one method for the removal along with the reaction for temporary hardness.
Answer
Temporary hardness-
By Boiling $—$ This method helps to remove only the temporary hardness of water. When temporary hard water is boiled, the bicarbonates of calcium and magnesium break up to form their insoluble carbonates.
These can be filtered out so that water becomes soft
$\underset{\text { (soluble calcium bicarbonate }}{\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2} \xrightarrow{\text { boild }} \underset{\text { (ppt)(calcium carbonate) }}{\mathrm{CaCO}_3}+\underset{\text { (water) }}{\mathrm{H} 2 \mathrm{O}}+\underset{\text { (carbon dioxide) }}{\mathrm{CO}_2(\mathrm{~g})}$
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[3 Mark Question Answer] - CHEMISTRY STD 8 Questions - Vidyadip