Solutions and Their Properties – Long Answer Questions
Medium Level (Application & Explanation)
Q1. Define a solution. Explain the roles of solute and solvent with suitable examples.
Answer:
A solution is a homogeneous mixture of two or more substances.
The solute is the substance that gets dissolved.
The solvent is the substance that dissolves the solute.
Example: In sugar in water, sugar is the solute, and water is the solvent.
The mixture looks uniform and clear because the solute spreads evenly.
You cannot see the solute particles as they are very small and well mixed.
Q2. Describe three important properties of solutions with examples.
Answer:
Solutions are clear and transparent. Light passes through without scattering.
They are homogeneous. Every part of the solution has the same composition.
There is no settling. The solute does not settle at the bottom on standing.
You can make solutions of variable concentration by adding more or less solute.
Example: Salt water remains clear and uniform even after hours.
Example: Sugar solution tastes uniformly sweet from top to bottom.
Q3. What do you mean by concentration of a solution? How can you increase or decrease it?
Answer:
Concentration tells how much solute is present in a given amount of solvent or solution.
A simple idea is: Concentration = amount of solute / amount of solution.
A solution with more solute is called concentrated.
A solution with less solute is called dilute.
You can increase concentration by adding more solute or removing some solvent.
You can decrease concentration by dilution (adding more solvent like water).
Q4. Explain why solutions are transparent while suspensions are cloudy.
Answer:
In a solution, particles are very small and evenly spread.
These tiny particles do not scatter light, so the solution looks transparent.
In a suspension, particles are larger and not fully dissolved.
These larger particles scatter light, so it looks cloudy.
Suspensions can also settle on standing, which makes them look uneven.
Example: Salt water is clear; sand in water looks cloudy and settles.
Q5. What is the Tyndall effect? Why is it seen in colloids but not in true solutions?
Answer:
The Tyndall effect is the scattering of light by small particles.
Colloids have tiny dispersed particles that can scatter light.
So, a light beam is visible when it passes through a colloid.
True solutions have even smaller particles that do not scatter light.
So, light passes through a true solution without a visible beam.
Example: A torch beam is visible in milk (colloid), but not in salt water (solution).
Q6. What is a suspension? State its features and give a common example.
Answer:
A suspension is a heterogeneous mixture of solid particles in a liquid.
The particles are not dissolved and are large enough to be seen under a microscope.
Suspensions are usually cloudy due to light scattering.
The particles can settle on standing, forming a sediment.
They can often be separated by filtration.
Example: Sand in water forms a suspension that settles at the bottom.
High Complexity (Analysis & Scenario-Based)
Q7. Three beakers contain: A—salt in water (clear), B—sand in water (settles), C—milk (opaque). Classify each and justify your answer using properties.
Answer:
Beaker A is a true solution. It is clear, homogeneous, and shows no settling.
Its particles are very small, so there is no Tyndall effect.
Beaker B is a suspension. It is cloudy and the particles settle over time.
The mixture is heterogeneous, and it can be filtered.
Beaker C is a colloid (like milk). It looks opaque and shows the Tyndall effect.
It does not settle on standing and cannot be easily filtered by ordinary filter paper.
Q8. You made lemonade that tastes too strong. Explain how you will dilute it and what happens to the concentration.
Answer:
The lemonade is concentrated because it has more solute (sugar, lemon, salt) per amount of solution.
To make it milder, add more solvent (water). This is called dilution.
The amount of solute stays the same, but the total solution volume increases.
So, the concentration decreases because solute per unit volume becomes less.
The mixture remains homogeneous and clear.
You can adjust the taste by adding water until the desired concentration is reached.
Q9. A student shines a torch through three liquids: salt solution, muddy water, and milk. Predict what they observe and explain why.
Answer:
In salt solution (true solution), the beam is not visible. No light scattering occurs.
In muddy water (suspension), the beam scatters and looks hazy due to large particles.
In milk (colloid), the beam is visible because of the Tyndall effect.
The difference is due to particle size: solution < colloid < suspension.
Suspensions may also settle, making the bottom murkier.
A filtration test can separate muddy water, but not milk or salt solution.
Q10. A mixture looks cloudy at first but becomes clear at the top after standing, leaving solid at the bottom. Explain what happened. Is it a solution, suspension, or colloid?
Answer:
The mixture is a suspension. It was cloudy due to large, undissolved particles.
On standing, particles settled due to gravity, forming a sediment at the bottom.
The top becomes clear because fewer particles remain in the upper part.
It is not a solution, because in a true solution there is no settling.
It is not a colloid, because colloids do not settle on standing.
You could filter the mixture to remove the solid, which confirms it is a suspension.
Q11. Two sugar–water samples taste different: Sample X is very sweet; Sample Y is mildly sweet. Explain using the concept of concentration and variable composition.
Answer:
Both are solutions, so they are homogeneous and clear.
Sample X has more sugar per amount of solution. It is more concentrated.
Sample Y has less sugar per amount of solution. It is more dilute.
Solutions can have variable composition. You can change the amount of solute.
The taste difference reflects their concentration difference.
By dilution or by adding more sugar, you can adjust the strength of either sample.
Q12. A friend says milk is a solution because it looks uniform. Do you agree? Justify using properties and tests.
Answer:
Milk is a colloid, not a true solution.
It looks uniform, but it has tiny fat globules dispersed in water.
It shows the Tyndall effect. A light beam is visible through milk.
It is often opaque or slightly cloudy, unlike clear solutions.
It does not settle like a suspension, and cannot be separated by simple filtration.
These features match colloids, not true solutions.
