Class 9 Science- Chapter 1- Matter In Our Surroundings – Activity 1.2: Observing Diffusion in Liquids (e.g., Making Tea, Lemonade)

Activity 1.2: Observing Diffusion in Liquids (e.g., Making Tea, Lemonade)

Objective

The purpose of this activity is to understand diffusion, a natural process where particles of one substance mix with another without any external force. It helps demonstrate how particles in liquids interact, move, and spread evenly.

Materials Needed

• A glass or beaker of water.
• Tea leaves or a tea bag.
• Lemon, sugar, and salt for lemonade.
• A spoon for stirring.
• Hot water for tea preparation.

Procedure

1. Making Tea:
   • Pour hot water into a glass or beaker.
   • Add a small quantity of tea leaves or place a tea bag into the water.
   • Observe how the tea leaves release color and flavor into the water. Stir if needed and note the changes.
2. Making Lemonade:
   • Take a glass of water.
   • Add one teaspoon of sugar and a pinch of salt to the water.
   • Squeeze a lemon into the water.
   • Stir the mixture thoroughly using a spoon.
3. Watch how each ingredient (sugar, salt, lemon juice) dissolves or mixes with the water.

Observations

• In tea preparation, the color and flavor of tea gradually spread into the water, even without stirring. This shows how the tea particles move on their own.
• In lemonade preparation, sugar and salt dissolve completely into the water after stirring, and lemon juice spreads evenly.
• In both cases, the liquid appears uniform after some time, with no visible chunks of sugar or salt and a consistent flavor throughout.

Also Check – Chapter 1 -MATTER IN OUR SURROUNDINGS -Class 9 – Simplified notes

Concepts Behind the Activity

1. What is Diffusion?
   Diffusion is the process where particles move from an area of higher concentration to an area of lower concentration. It happens until the particles are evenly distributed.
   Example: When tea leaves are added to hot water, the particles of tea move out of the leaves and mix into the water.
2. Why Diffusion Happens in Liquids:
   • Constant Particle Motion: Particles in liquids are always moving because they have energy. This motion allows the particles to collide and spread out.
   • Spaces Between Particles: Liquid particles are loosely packed compared to solids. The spaces between them allow other particles, like sugar or salt, to fit and mix.
3. Effect of Stirring and Temperature:
   • Stirring speeds up diffusion because it physically helps mix the particles.
   • Hot water increases particle movement, which makes diffusion faster. For example, tea spreads more quickly in hot water than in cold water.

Learning Outcomes

1. Diffusion is a Natural Process:
   Particles in liquids move and mix on their own due to their constant motion.
2. Liquids Have Space Between Particles:
   Sugar, salt, or tea particles dissolve because they move into the spaces between water particles.
3. Factors Affecting Diffusion:
   • Temperature: Higher temperatures increase the energy of particles, making diffusion faster (e.g., tea dissolves faster in hot water).
   • Stirring: Helps mix particles physically, speeding up diffusion.
4. Uniform Mixing:
   Diffusion ensures a uniform mixture, which is why tea or lemonade tastes the same throughout.

Applications of Diffusion

• Preparing drinks like tea, coffee, or lemonade.
• Absorption of nutrients in the human body, such as dissolved oxygen in water reaching aquatic animals.
• Spreading of flavors and smells in food and drinks.

Intext and additional Question Answers on Activity Activity 1.2: Observing Diffusion in Liquids (e.g., Making Tea, Lemonade)

Question: Is the water still colored after repeated dilution?
Yes, even after repeated dilution, the water retains a faint color. This demonstrates that the particles of potassium permanganate are incredibly small and can distribute evenly throughout a large volume of water, even in trace amounts.

Additional Question: What does the faint color after many dilutions tell us about the size of particles in matter?
The faint color indicates that the particles of matter are extraordinarily small, so much so that even a single crystal of potassium permanganate contains millions of particles capable of coloring an enormous amount of water. This reveals the particulate nature of matter and its divisibility.

Conclusion

This activity shows that diffusion in liquids occurs because particles are always in motion and have space between them. This property allows substances like tea, sugar, and salt to mix and dissolve in water evenly. It explains why liquids can form uniform mixtures without requiring force and highlights the behavior of particles in liquids.