This MCQ module is based on: Evaporation, Condensation and Crystallisation
TOPIC 33 OF 46
Evaporation, Condensation and Crystallisation
🎓 Class 6
Science
CBSE
Theory
Ch 9 — Methods of Separation of Substances
⏱ ~14 min
🌐 Language: [gtranslate]
🧠 AI-Powered MCQ Assessment
▲
Myaischool Lt Science Assessment
▲
[myaischool_lt_science_assessment grade_level="class_6" science_domain="chemistry" difficulty="basic"]
9.11 Evaporation — Getting Salt from Seawater
In Part 2 we saw that sieving and filtration do not work on salt water, because salt has dissolved into the water. So how does India make so much salt? The answer is a very old, very clever method called evaporation.
Along the coasts of Gujarat, Tamil Nadu and Odisha, sea water is led into shallow mud-walled pools called salt pans. The sun shines all day and the wind blows across the pools. Day by day, the water slowly turns into water vapour and disappears into the air. But the salt cannot evaporate — it is left behind as shining white crystals on the pan floor.
Evaporation: The quiet escape of liquid particles into the air as gas. It happens all day, even without boiling — from puddles, clothes on a line, and the damp floor after a mop.
Activity 9.5 — Make Your Own Salt L3 Apply
You need: 1 tsp common salt, half a cup of warm water, a dark-coloured plate (a steel katori works), a sunny window-sill.
- Stir the salt in the warm water until no grains remain.
- Pour a thin layer of the salt water onto the plate.
- Place the plate on a sunny window-sill and leave it for 1–2 days.
- Watch the water slowly shrink. On day 2, carefully feel the plate.
Predict: Will there be anything left on the plate when the water is gone? What will it taste like? (Do not eat it — just guess.)
Observation: The water vanishes into the air, but the salt is left behind as tiny white specks on the plate. That is because only the water particles could escape as vapour — the salt particles stayed behind. This is exactly how salt is made from seawater!
9.12 Condensation — Catching the Vapour Again
Evaporation gives us salt, but the water is lost into the air. What if we actually want the water, not the salt? We can trap the rising vapour by cooling it. The vapour turns back into liquid water. This change is called condensation.
Where You See Condensation Every Day
- Tiny water drops on the lid of a pan while cooking rice.
- Fog on the bathroom mirror after a hot shower.
- Water on the outside of a cold glass of nimbu-paani.
- Dew settling on morning grass.
Evaporation + condensation = getting pure water! When we evaporate salt water and then catch the vapour on a cool surface, the vapour becomes pure water — free of salt. This is how old sailors and desert travellers made drinking water from seawater.
Activity 9.6 — Catching Water Drops L4 Analyse
You need: a small pan of warm (not boiling) salted water, a steel plate from the fridge (cold), oven mitts.
- With an elder's help, heat the salted water in the pan so it steams a little (do not boil it).
- Hold the cold steel plate (wearing oven mitts) 10 cm above the pan for one minute.
- Look at the underside of the plate.
- Carefully tip the drops onto a clean spoon. Taste one tiny drop.
Predict: The pan had salt water. Will the drops on the plate be salty too?
Observation: The drops are not salty! Only water particles could leave the pan as vapour — the salt stayed behind. When the vapour touched the cool plate, it condensed back into pure water. This is how evaporation and condensation together give us clean drinking water.
9.13 Crystallisation — Beautiful Crystals Grow!
Sometimes when we evaporate a solution slowly and carefully, the solid comes back not as a dusty powder, but as shiny, regular-shaped crystals. This method is called crystallisation.
Crystallisation gives us purer and better-looking solid than plain evaporation does. Scientists and factories use it to purify sugar, salt, tartaric acid, and chemicals like copper sulphate — which makes beautiful blue crystals.
Crystal: a solid whose particles are lined up in a very neat, repeating pattern — which is why it has flat faces and a regular shape.
9.14 Combining Methods — Real-Life Mixtures
Real mixtures often need more than one method. Look at this example:
Problem: A mixture has sand, iron filings, salt, and water. How do we separate all four?
| Step | Method | What we get |
|---|---|---|
| 1 | Magnetic separation | Iron filings removed with a magnet |
| 2 | Filtration (or sedimentation + decantation) | Sand caught on filter paper; salt water passes through |
| 3 | Evaporation of the salt water | Salt crystals remain; water lost as vapour |
| 3(b) | Evaporation + condensation | Both salt and pure water are collected |
9.15 Purifying Water — Old Wisdom of India
Our grandparents and great-grandparents had no water filters with electric pumps. Yet they drank safe, clean water. How? By combining simple separation methods — passed down for hundreds of years.
Matka Storage
Water stored overnight in an earthen pot. Sediment settles; the clay also cools and freshens the water.
Strainer Herbs
Leaves of the drumstick tree (moringa) and seeds of nirmali were crushed into water to help mud settle faster.
Boiling
After decanting, water was boiled — killing germs. Used for drinking water in hostels and temples even today.
Sand Filter Pots
A three-layer pot of pebbles, coarse sand and fine sand — water poured on top comes out much cleaner at the bottom.
Activity 9.7 — Build a Mini Water Purifier L5 Evaluate
You need: a large empty plastic bottle (cut in half), pebbles, coarse sand, fine sand, a cotton wool pad, a glass to collect water, a glass of muddy water.
- Turn the top half of the bottle upside down, like a funnel. Plug its mouth with cotton wool.
- Layer inside, from bottom to top: cotton → fine sand (4 cm) → coarse sand (3 cm) → small pebbles (3 cm).
- Place this funnel over an empty glass.
- Pour muddy water slowly into the pebble layer.
- Observe the water dripping out below.
Predict: Will the water coming out be clear, a little cloudy, or still muddy?
Observation: The water comes out much clearer! The pebbles stop large bits, the sand traps finer particles, and the cotton catches the tiniest ones. This is filtration using three layers of different particle sizes — the same idea as in Indian sand filters. But remember — the water may still have germs, so it is not safe to drink without boiling.
Competency-Based Questions
In a salt pan in Tuticorin (Tamil Nadu), Ravi watches sea water sitting in shallow pools. Day by day, the water level falls and by the end of the week a sparkling white crust forms on the floor. The salt is scraped up, packed, and sent to markets all over India.
Q1. Which method is at work in the salt pan? L1
C — Evaporation. The sun's heat slowly turns the water into water vapour, which rises into the air, leaving solid salt behind.
Q2. Why is the salt left behind while only the water escapes? L3
Only the water particles can turn into vapour and fly into the air under normal sun heat. The salt particles need a much higher heat to evaporate, so they stay behind as solid crystals.
Q3. Ravi's cousin wants pure water from sea water, not salt. How can Ravi collect the rising vapour and turn it back into water? L4
Cover the pan with a cool inverted plate or a sloping glass sheet. The vapour hits the cool surface and condenses into liquid water drops, which slide down and can be collected in another vessel. The combination is evaporation + condensation.
Q4. Fill in the blanks: When a hot solution is cooled slowly, the dissolved solid may form beautiful regular-shaped ______, and this method is called ______. L1
crystals ; crystallisation.
Q5. A mixture has iron dust, sand, and salt dissolved in water. Write the steps Ravi should follow in the correct order. L5
(1) Use a magnet to remove iron dust. (2) Filter the liquid — sand stays on the filter paper, salt water passes through. (3) Evaporate the salt water (or crystallise it) to get salt. This way every component is separated.
Assertion – Reason
Assertion (A): Evaporation can separate salt from salt water.
Reason (R): Water changes into vapour easily, but salt does not.
Answer: A. The whole salt-pan idea works because only water can evaporate at everyday temperatures. Salt is left behind as crystals.
Assertion (A): Water drops appear on the outside of a cold glass of lemonade on a hot afternoon.
Reason (R): The drops come from water vapour in the air condensing on the cold glass surface.
Answer: A. Air carries invisible water vapour. When this vapour touches the cold glass, it cools and turns into tiny liquid drops — exactly the reason given.
Assertion (A): Crystallisation gives a purer solid than ordinary evaporation.
Reason (R): In crystallisation, the solid particles arrange themselves in a neat, regular pattern as they come out of the solution.
Answer: A. Because the particles line up neatly, impurities are pushed out of the crystal, giving a purer solid. The reason explains the assertion.
Frequently Asked Questions — Evaporation, Condensation and Crystallisation
What does the topic 'Evaporation, Condensation and Crystallisation' cover in Class 6 Science?
The topic 'Evaporation, Condensation and Crystallisation' is part of NCERT Class 6 Science Chapter 9 — Methods of Separation in Everyday Life. It covers the key ideas of evaporation, condensation, crystallisation, salt from seawater, pure solid, solution, explained through everyday examples, labelled diagrams and hands-on activities from the NCERT Curiosity textbook. Class 6 students learn simple definitions, see why each idea matters in daily life, and try short experiments and observations. The lesson uses easy language, colourful pictures and small questions so that young learners build a strong base for higher classes and for competency-based questions in CBSE school tests.
Why is 'Evaporation, Condensation and Crystallisation' important for Class 6 NCERT Science?
'Evaporation, Condensation and Crystallisation' is important because it builds the first ideas of science that Class 6 students will use again in Class 7, 8 and beyond. NCERT Chapter 9 — Methods of Separation in Everyday Life — introduces evaporation and connects it to things children already see at home, at school and in nature. Learning this topic helps students ask better questions, understand simple news about science, and score well in CBSE tests that use competency-based questions. The chapter also supports NEP 2020 by encouraging curiosity, observation and learning by doing rather than only reading and memorising.
What are the key ideas students should remember from Evaporation, Condensation and Crystallisation?
The key ideas in 'Evaporation, Condensation and Crystallisation' for Class 6 Science are: evaporation, condensation, crystallisation, salt from seawater, pure solid, solution. Students should be able to say each term in their own words, give one or two easy examples from daily life, and draw a small labelled diagram where needed. A good way to revise is to make flashcards, write a short note in the science notebook, and solve the NCERT in-text and exercise questions of Chapter 9. Linking every idea to something seen at home or school — in the kitchen, garden, playground or sky — makes these ideas easy to remember for unit tests and the annual CBSE examination.
How is Evaporation, Condensation and Crystallisation taught using activities in NCERT Curiosity Class 6?
NCERT Curiosity Class 6 Science teaches 'Evaporation, Condensation and Crystallisation' through an inquiry-based approach using Predict–Observe–Explain activities. Students first make a guess, then try a small experiment with safe, easily available materials, and finally explain what happened and why. This matches the NEP 2020 focus on learning by doing. For Chapter 9 — Methods of Separation in Everyday Life — the textbook has hands-on tasks, labelled pictures and thinking questions built for Bloom's Taxonomy Levels 1 to 6. Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding instead of only rote learning.
What real-life examples of evaporation can Class 6 students see at home?
Class 6 students can see evaporation at home in many simple ways linked to 'Evaporation, Condensation and Crystallisation'. Kitchens, school bags, playgrounds, the garden and the night sky are full of examples that match NCERT Chapter 9 — Methods of Separation in Everyday Life. For example, students can look at food labels, watch changes while cooking, try safe activities with water, magnets or shadows, and observe the Sun, Moon and weather each day. Keeping a small science diary — with the date, what was observed and a quick drawing — turns daily life into a mini science lab. These real-life links make concepts easy to remember and help in answering competency-based questions in CBSE Class 6 Science.
How does 'Evaporation, Condensation and Crystallisation' connect to other chapters of Class 6 Science?
'Evaporation, Condensation and Crystallisation' connects to many other chapters in NCERT Class 6 Science Curiosity. The ideas of evaporation come back when students study related topics like diversity in the living world, food, magnets, measurement, materials, temperature, water, separation, habitats, natural resources and the solar system. For example, what students learn here helps them build mental pictures for later chapters and for Class 7 and Class 8 Science. Teachers often ask cross-chapter questions in CBSE exams to check if students can use what they learned in Chapter 9 — Methods of Separation in Everyday Life — in new situations. This linked approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
AI Tutor
Science Class 6 — Curiosity
Ready