Class8 Science Book Curiosity Chapter 9 QA
Class 8 – Science | Chapter 9
VERY SHORT ANSWER (1 MARK) – IMPORTANT
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What is density?
Density is the mass per unit volume of a substance. -
State the formula of density.
Density = Mass ÷ Volume -
What is solubility?
Solubility is the maximum amount of solute that dissolves in a fixed amount of solvent at a given temperature. -
What is a saturated solution?
A solution that cannot dissolve more solute at a given temperature. -
What is an unsaturated solution?
A solution that can dissolve more solute at a given temperature. -
Name the instrument used to measure mass.
Physical balance. -
Name the instrument used to measure volume of liquids.
Measuring cylinder.
SHORT ANSWER (2 MARKS) – IMPORTANT
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Define solute and solvent.
Solute is the substance that dissolves in a solvent.
Solvent is the substance that dissolves the solute. -
What is concentration of a solution?
Concentration is the amount of solute present in a given amount of solvent or solution. -
Differentiate between dilute and concentrated solutions.
Dilute solution contains less solute.
Concentrated solution contains more solute. -
How does temperature affect solubility of solids?
Solubility of solids increases with increase in temperature. -
How does temperature affect solubility of gases?
Solubility of gases decreases with increase in temperature. -
Write the conversion factor of density.
1 g/cm³ = 1000 kg/m³
LONG ANSWER (5 MARKS) – IMPORTANT
1. Explain solute, solvent and solution with example.
A solute is the substance that dissolves in another substance.
A solvent is the substance that dissolves the solute.
A solution is a homogeneous mixture of a solute and a solvent.
Example: Salt dissolved in water forms salt solution.
2. Explain saturated and unsaturated solutions.
An unsaturated solution can dissolve more solute at a given temperature.
A saturated solution cannot dissolve any more solute at the same temperature.
3. What is solubility? How is it measured?
Solubility is the maximum amount of solute that dissolves in a fixed amount of solvent at a given temperature.
It is measured by adding solute to the solvent until no more solute dissolves.
4. Why do objects float or sink in water?
Objects float if their density is less than the density of water.
Objects sink if their density is greater than the density of water.
5. Define density. Write formula and conversion factor.
Density is the mass per unit volume of a substance.
Formula: Density = Mass ÷ Volume
Conversion factor: 1 g/cm³ = 1000 kg/m³
6. How are mass and volume measured?
Mass is measured using a physical balance.
Volume of liquids is measured using a measuring cylinder.
Volume of irregular solids is measured using water displacement method.
7. Effect of temperature and pressure on density.
Increase in temperature decreases density due to increase in volume.
Increase in pressure increases density as particles come closer.
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