Anomalous Expansion of water

•    Anomalous expansion of water is defined as the expansion of water when it is cooled from four degree celsius to zero degree celsius.
•    Volume and density of water changes in different ways when heated from zero degree celsius to ten degree celsius.

                                             

The volume of water first decreases on heating it from zero degree celsius to four degree celsius and is minimum at four degree celsius.
On further heating the water above four degree celsius, the volume starts to increase.

                                          

When water is heated from zero degree celsius, the density of water first increases from zero degree celsius to four degree celsius and then decreases above four degree celsius to ten degree celsius.
The density of water is maximum at four degree celsius.
•    Hope’s conducted for the first time an experiment to demonstrate anomalous expansion of water. The apparatus used by Hope is called the Hope’s apparatus.

                                              

•    Some consequences of anomalous expansion of water are freezing the top layer of lakes and ponds, bursting of water pipes and damage to crops.
 

 

 

 

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  • Q1

    In extremely cold regions, anomalous expansion of water

    Marks:1
    Answer:

    saves aquatic life

    Explanation:

    During extreme cold temperatures in colder regions, only top layer of the water bodies (such as lakes, ponds, etc.) get frozen due to anomalous expansion of water. The temperature of the lower layers of water remains between 0oC to 4oC which is optimum for existence of aquatic animals.

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  • Q2

    When water is heated from 0oC to 10oC, its volume

    Marks:1
    Answer:

    first decreases and then increases

    Explanation:

    Due to anomalous expansion of water between a temperature range of 0oC to 4oC, it contracts, i.e., water molecules come closer and hence its volume decreases. On further heating, it starts to expand (molecules get farther from each other) and the volume increases.

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  • Q3

    When water is heated from 0oC to 10oC, its density

    Marks:1
    Answer:

    first increases and then decreases

    Explanation:

    Due to anomalous expansion of water between a temperature range of 0oC to 4oC, it contracts, i.e., water molecules come closer and hence, its density increases. On further heating, it starts to expand (molecules get farther from each other) and the density decreases.

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  • Q4

    Selina took a vessel filled with water and put it into the ice section of the refrigerator. She took out the vessel after sometime and observed that initially the water was frozen

    Marks:1
    Answer:

    from the top but not from the bottom

    Explanation:

    When water starts to cool, it becomes denser. The denser layer of water settles down replacing the lighter layer. As a result, the lighter layer goes to top. On reaching a temperature of 4oC, the water starts to expand on further cooling due to anomalous expansion which decreases its density. Thus, the top layer remains on top and freezes first.

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  • Q5

    Roger took icy chilled water and boiled it to 10oC. The water will

    Marks:1
    Answer:

    first contract and then expand

    Explanation:

    Icy chilled water suggests that its temperature is approximately 0oC. The water will first contract due to anomalous expansion till it achieves a temperature of 4oC and then it will expand.

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