The Amazing World of Solutes Solvents and Solutions Notes

The Amazing World of Solutes Solvents and Solutions Notes Class 8 Science Curiosity NCERT

1. What is a Solution?

A solution is a homogeneous mixture of two or more substances.

• Homogeneous = looks the same throughout.

Examples

Salt water, sugar water, lemonade, air (mixture of gases).

2. Solute & Solvent

Every solution has two main parts:

✔ Solvent

• The substance present in larger amount
• It dissolves the other substance
• Usually a liquid

Examples

Water, milk, alcohol.

✔ Solute

• The substance that gets dissolved
• The substance present in smaller amount

Examples

Salt, sugar, lemon juice, carbon dioxide (in soft drinks).

3. Types of Solutions

Solutions can be of different types depending on the state of solute and solvent:

(a) Solid in Liquid

• Salt in water
• Sugar in water

(b) Gas in Liquid

• CO₂ dissolved in cold drinks
• Oxygen dissolved in water (helps aquatic life)

(c) Liquid in Liquid

• Vinegar in water
• Alcohol in water

(d) Solid in Solid

• Alloys like brass (copper + zinc)

4. Solubility

Solubility = How much solute can be dissolved in a given amount of solvent.

• Hot water dissolves more sugar/salt than cold water.
• Stirring increases solubility.
• Fine powders dissolve faster than big crystals.

5. Factors Affecting Solubility

1. Temperature
   • ↑ Temperature → ↑ Solubility (for solids)
   • ↑ Temperature → ↓ Solubility (for gases)
2. Stirring / Agitation
   • Dissolves solute faster.
3. Surface Area
   • Powdered solute dissolves faster than crystals.

6. Saturated, Unsaturated & Supersaturated Solutions

✔ Unsaturated Solution

• Can dissolve more solute.
• Example: 1 spoon sugar in a glass of water.

✔ Saturated Solution

• Cannot dissolve any more solute at that temperature.
• Extra solute settles at the bottom.

✔ Supersaturated Solution (Rare)

• Contains more solute than it normally can hold (unstable).
• Formed by heating → dissolving extra solute → cooling.

7. Concentrated & Dilute Solutions

✔ Dilute Solution

• Has less solute.
• Example: Light coloured lemonade.

✔ Concentrated Solution

• Has more solute.
• Example: Thick sugar syrup.

9. Water: The Universal Solvent

• Water dissolves more substances than any other liquid.
• Because its molecules attract solute particles strongly.
• That’s why it is called a universal solvent

10. Everyday Examples of Solutions

• Tea = water (solvent) + tea extract + sugar + milk (solutes)
• Lemonade = water + sugar + lemon juice
• Soft drink = water + sugar + CO₂ gas
• Perfume = alcohol + fragrance oils

11. Uses of Solutions in Daily Life

• Medicine syrups
• Saline water for hospitals
• Jewellery making (alloys)
• Food industry (juices, drinks, syrups)
• Cleaning (detergent dissolved in water)

12.Difference Between Solution, Suspension & Colloid

• Solution: Clear, particles don’t settle.
• Suspension: Cloudy, particles settle.
• Colloid: Cloudy but stable, particles don’t settle.

Key Terms (Exam Friendly)

• Solute: Substance dissolved
• Solvent: Medium in which solute dissolves
• Solution: Homogeneous mixture
• Solubility: Maximum solute that dissolves in a solvent
• Saturated: No more solute dissolves
• Unsaturated: Can dissolve more solute
• Concentrated/Dilute: Amount of solute present