Water Quiz - ICSE Class 8 Science
Free practice quiz: Water (ICSE Class 8 Science). 48 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Which property of water makes it an excellent solvent for ionic compounds?
- High surface tension
- High specific heat capacity
- Polar nature
- Abundance on Earth
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Answer: C. Polar nature
Water molecules are polar, meaning they have a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows water to attract and surround the ions of ionic compounds, effectively dissolving them.
When water is heated, its volume increases, but its mass remains constant. This is an illustration of the:
- Law of Conservation of Mass
- Law of Conservation of Energy
- Principle of Buoyancy
- Archimedes' Principle
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Answer: A. Law of Conservation of Mass
The Law of Conservation of Mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. While the volume of water changes with temperature, its mass (the amount of matter) remains the same.
The process of groundwater seeping to the surface to form springs is an example of:
- Infiltration
- Percolation
- Runoff
- Discharge
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Answer: D. Discharge
Discharge is the release of water from an aquifer or groundwater system onto the surface of the Earth, often forming springs, rivers, or seeps.
Water molecules have a polarity due to:
- The equal sharing of electrons between oxygen and hydrogen
- The bent shape of the molecule and the electronegativity difference between oxygen and hydrogen
- The presence of only hydrogen atoms
- The high melting point of ice
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Answer: B. The bent shape of the molecule and the electronegativity difference between oxygen and hydrogen
Oxygen is more electronegative than hydrogen, meaning it attracts electrons more strongly. This creates partial negative charge on oxygen and partial positive charges on hydrogen. The bent shape of the water molecule prevents these partial charges from canceling each other out, resulting in an overall molecular polarity.
The difference between temporary and permanent water hardness is primarily due to:
- The presence of sodium ions
- The type of dissolved salts causing the hardness
- The total amount of dissolved solids
- The pH of the water
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Answer: B. The type of dissolved salts causing the hardness
Temporary hardness is caused by dissolved bicarbonates of calcium and magnesium, which can be removed by boiling. Permanent hardness is caused by dissolved sulfates and chlorides of calcium and magnesium, which require other methods like ion exchange to remove.