NCERT Solutions for Class 6 Science Chapter 08 A Journey through States of Water

Question 1. Which of the following best describes condensation?
(i) The conversion of water into its vapour state.
(ii) The process of water changing from a liquid into gaseous state.
(iii) The formation of clouds from tiny water droplets.
(iv) The conversion of water vapour into its liquid state.
Answer: (iv) The conversion of water vapour into its liquid state.
In simple words: Condensation means when water vapour turns back into liquid water. This happens when steam cools down.

Exam Tip: Remember that condensation is the opposite of evaporation - it changes gas into liquid, not liquid into gas.

Question 2. Identify in which of the given processes, evaporation is very important.
(i) Colouring with
(a) crayons                   (b) water colours
(c) acrylic colours             (d) pencil colours
(ii) Writing on paper with
(a) pencil                   (b) ink pen
(c) ball point pen
Answer:
(i) (b) water colours
(ii) (b) ink pen
In simple words: Water colours need evaporation to dry on paper after you paint. Ink pens also need evaporation to dry the ink on the paper.

Exam Tip: Look for processes where a liquid needs to disappear or dry - that's where evaporation plays an important role.

Question 3. We see green coloured plastic grass at many places these days. Space around natural grass feels cooler than space around the plastic grass. Can you find out why?
Answer: The space around natural grass feels cooler because natural grass takes in water and releases it back into the air through transpiration and evaporation. This process takes heat away from the air, which cools the surroundings. Plastic grass does not have this property, so it cannot create the same cooling effect that natural grass provides.
In simple words: Real grass cools the air around it by letting water rise up and vanish into the air. Plastic grass cannot do this, so the space around it stays hotter.

Exam Tip: When comparing natural and plastic materials, always think about water and evaporation - these are often the keys to understanding temperature differences.

Question 4. Give examples of liquids other than water, which evaporate.
Answer: Examples of liquids other than water that evaporate include alcohol, acetone, and petrol. These liquids turn into vapour when left exposed to the air.
In simple words: Alcohol, acetone, and petrol all dry up and disappear into the air like water does.

Exam Tip: Remember that evaporation is not just a water property - many other liquids can evaporate too. Think of perfume, nail polish remover, and fuel as common examples.

Question 5. Fans move air around, creating a cooling sensation. It might seem strange to use a fan to dry wet clothes since fans usually make things cooler, not warmer. Normally, when water evaporates, it requires heat, not cold air. What do you think about this?
Answer: Fans help dry wet clothes by pushing air over them, which speeds up the rate of evaporation. Although fans make the air feel cooler, they actually help evaporation by moving wet, heavy air away from the clothes and replacing it with drier air. This carries away more moisture from the cloth surface, making the clothes dry faster.
In simple words: A fan moves fresh, dry air onto the wet clothes. This dry air picks up water from the cloth and carries it away, helping the cloth dry quicker.

Exam Tip: The key concept is that fans increase evaporation by removing humid air from the cloth surface, not by adding heat - air circulation matters as much as temperature.

Question 6. Usually, when sludge is removed from drains, it is left in heaps next to the drain for 3-4 days. Afterward, it is transported to a garden or a field where it can be used as manure. This approach reduces transportation cost of the sludge and enhances the safety of individuals handling it. Reflect upon it and explain how.
Answer: When sludge sits in heaps for 3-4 days, some of the water in it evaporates. This reduces both the weight and the volume of the sludge. Because the sludge becomes lighter and smaller, it costs less money to move it to the garden or field. Also, handling drier sludge is safer for workers because it is less likely to spill or spread harmful germs and contamination.
In simple words: Leaving sludge to dry for a few days makes it lighter and smaller through evaporation. This saves money on moving it and keeps workers safer.

Exam Tip: Focus on how evaporation reduces weight and volume, leading to both cost savings and safety improvements in waste handling.

Question 7. Observe the activities in your house for a day. Identify the activities that involve evaporation. How does understanding the process of evaporation help us in our daily activities?
Answer: Activities that involve evaporation in the home include drying clothes, cooking (boiling water), sweating, and using hand sanitizers. Understanding evaporation helps us make these activities more efficient. For example, we know that spreading clothes out on a line makes them dry faster, or that using a fan speeds up drying. We also know that sweating helps cool our bodies, and that hand sanitizers dry quickly because of evaporation.
In simple words: Many daily tasks use evaporation - drying clothes, cooking, and cooling our bodies. When we understand evaporation, we can do these tasks faster and better.

Exam Tip: List at least 3-4 household activities involving evaporation and explain one way that understanding evaporation helps with each activity.

Question 8. How is water present in the solid state in nature?
Answer: Water is present in the solid state in nature as:

➤ Ice - Found in glaciers, ice caps, and icebergs.
➤ Snow - Commonly found in mountainous regions and during winter seasons.
➤ Hail - Solid precipitation in the form of balls or lumps of ice.
➤ Frost - A thin layer of ice that forms on surfaces when the temperature drops below freezing.

In simple words: Water freezes into ice, snow, hail, and frost in different places around the world. All of these are solid water found in nature.

Exam Tip: Remember the four main forms of solid water in nature and where each one is typically found - examiners often ask for specific examples and locations.

Question 9. Reflect on the statement "Water is our responsibility before it is our right." Share your thoughts.
Answer: This statement highlights that we must focus on caring for and protecting water before thinking about using it ourselves. Water is vital for all life, and everyone deserves access to clean water. However, our first duty is to use water wisely, avoid wasting it, and keep it clean for everyone. We must protect water sources so that clean water will be available for future generations and all people living today.
In simple words: We should take care of water first by not wasting it and keeping it safe. Then we can enjoy having clean water to use.

Exam Tip: This reflective question looks for awareness of water conservation and social responsibility - mention both personal duty and the needs of future generations in your answer.

Question 10. The seat of a two-wheeler parked on a sunny day has become very hot. How can you cool it down?
Answer: To cool down the hot seat of a two-wheeler parked on a sunny day, we can:

➤ Cover it with a wet cloth: Place a damp cloth or towel over the seat. The water will take in heat as it evaporates, cooling the seat.

➤ Sprinkle water on it: Lightly spray water directly on the seat. The evaporating water will help lower the temperature.

➤ Use a sunshade or cover: If available, use a sunshade or seat cover to protect the seat from direct sunlight, which will help keep it cooler.

➤ Park in the shade: If possible, move the two-wheeler to a shaded area to reduce the seat's exposure to direct sunlight.

In simple words: Wet cloth, water spray, sunshade, or parking in shade all help cool a hot seat by stopping direct sun heat or by using evaporation.

Exam Tip: The examiner looks for practical solutions using the concept of evaporation cooling - mention at least two methods and explain how evaporation plays a role in each.