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The Amazing World of Solutes, Solvents, and Solutions - Floating, Sinking, and Density

Grade 5CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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A Solute is the substance that dissolves in a liquid (e.g., sugar or salt).

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A Solvent is the liquid in which the solute dissolves. Water (H2OH_2O) is known as the 'Universal Solvent'.

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A Solution is a homogeneous mixture formed when a solute dissolves completely in a solvent: Solute+Solvent=SolutionSolute + Solvent = Solution.

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Density is the measure of how much mass is contained in a given volume. It is expressed as Density=MassVolumeDensity = \frac{Mass}{Volume}.

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An object will float if its density is less than the density of the liquid (Density of water ≈1 g/cm3\approx 1\,g/cm^3).

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An object will sink if its density is greater than the density of the liquid.

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Adding salt to water increases the density of the solution. This is why it is easier to float in the Dead Sea than in a freshwater lake.

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A Saturated Solution is a solution in which no more solute can be dissolved at a specific temperature.

📐Formulae

Density=MassVolumeDensity = \frac{Mass}{Volume}

Solute+Solvent=SolutionSolute + Solvent = Solution

D=mVD = \frac{m}{V}

💡Examples

Problem 1:

If a stone has a mass of 100 g100\,g and occupies a volume of 20 cm320\,cm^3, what is its density? Will it sink or float in water?

Solution:

Density=100 g20 cm3=5 g/cm3Density = \frac{100\,g}{20\,cm^3} = 5\,g/cm^3

Explanation:

Since the density of the stone (5 g/cm35\,g/cm^3) is much higher than the density of water (1 g/cm31\,g/cm^3), the stone will sink.

Problem 2:

Explain why a lemon sinks in plain water but floats when a lot of salt is dissolved in the same water.

Solution:

DensitySalt Water>DensityLemon>DensityPlain WaterDensity_{Salt\,Water} > Density_{Lemon} > Density_{Plain\,Water}

Explanation:

In plain water, the lemon is denser than the water, so it sinks. Adding salt increases the mass of the water without changing its volume significantly, thereby increasing its density. Once the water's density becomes higher than the lemon's density, the lemon floats.

Problem 3:

Identify the solute and solvent in a solution prepared by mixing 10 g10\,g of sugar in 100 ml100\,ml of water.

Solution:

Solute = Sugar; Solvent = Water (H2OH_2O)

Explanation:

The substance being dissolved (sugar) is the solute, and the substance doing the dissolving (water) is the solvent.