A Journey through States of Water Class 6 Questions and Answers NCERT Solutions
Class 6 Science Chapter 8 A Journey through States of Water
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Question 1.
Which of the following describes condensation?
(i) Conversion of water changing into its vapour state.
(ii) The process of water changing from a liquid into gaseous state.
(iii) The formation of cloud 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.
Question 2.
Identify in which of the given process, evaporation is very important.
(i) Colouring with
(a) Crayons
(b) Water colours
(c) Acrylic colours
(d) Pencil colours
Answer:
(b) Water colours
(ii) Writing on paper with
(a) Pencil
(b) Ink pen
(c) Ball point pen
Answer:
(b) Ink pen
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:
Water is lost from the natural grass from the aerial part of the leaves (transportation) and evaporation. Evaporation causes cooling effect.
Question 4.
Give examples of liquids other than water which evaporate?
Answer:
Acetone (nail polish remover), ether, ethyl chloride, saniterzer, oil, milk, etc.
Question 5.
Fans move 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, if requires heat, not cold air. What do you think about this?
Answer:
Fan increases air speed. Hence, the particles of water move away with the air thereby decreasing the water vapour in the surroundings. As a rest, the rate of evaporation increases. Hence wet clothes dry quickly.
Question 6.
Usually when sludge is removed from drains, it is left in heaps next to the drains for 3-4 days. Afterwards, it is transported to a garden or a field where it can be used as manure. This approach reduces transportation lost of sludge and enhances the safety of individuals handling it. Reflect upon it and explain how.
Answer:
Sludge is taken out from the drains. The sludge is dried and used as a manure. The use of dried sludge as a manure returns the nutrients to the soil.
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:
The activities are:
- We sprinkle water on the roof or open ground in summer.
- We wear cotton clothes in summer.
- Perspiration keeps our body cool.
- Water kept in earthen pot becomes cool. Thus, evaporation helps us in our daily activities.
Question 8.
How is water present in the solid state in nature?
Answer:
Water in the solid form occurs as ice and snow on the peaks of mountains and in the polar regions such as Antartica.
Question 9.
Reflect on the statement, “Water is our responsibility before it is our right”. Share your thoughts.
Answer:
Increase in population has added to the demand of water to meet their requirements. Water pollution has also reduced the availability of usable water. The most important source of usable water is underground water, such as, well water.
The underground water is being used more and more for industrial and agricultural purposes. As a result, the level of underground water is falling. It is important that we use water carefully and waste it. So, water is our responsibility before it is our right.
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 absorb heat as it evaporates,cooling the seat.
- Sprinkle water on it: Lightly sprinkle water directly on the seat. The evaporating water will help to 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.
Activities:
Activity 1.
Aim: To show that ice and water are the same substances.
Materials Required : A cup, an ice cube.
Procedure:
- Put an ice cube in a cup
- Leave it on the table and observe
Observations: Ice gets converted into water.
Conclusion: Ice and water are the same substance. They are the two forms of the same substances.
Activity 2.
Aim: To show disappearance of water kept on a steel plate.
Materials Required：A steel plate, a tablespoon of water.
Procedure :
- Take a tablespoon of water on a steel plate.
- Observe whether water seeps through to the other side of the plate or not.
- Keep observing it at regular intervals.
Observations: The water completely disappears.
Conclusion: Water does not seep through the steel plate. Water disappears due to evaporation of water from its surface. This water coverted into gaseous state called water vapour.
While making Dosa, we sprinkle some water on the hot pan and it disappears. The water which is sprinkled on the hot pan gets converted into steam. Steam is actually water vapour, some part of which converts into water droplets.
The process of conversion of water into its vapour state is called evaporation.
The process of evaporation takes place continuously, even at room temperature.
Activity 3.
Aim: To show condensation process.
Materials Required : A glass tumbler, cold water, ice cubes.
Procedure :
- Take cold water in a glass tumbler
- Add a few ice-cubes into it
- Leave it undisturbed for five minutes
Observations:
| I observe | I wonder |
| A large number of tiny drops of water appear on the outer surface of the glass. | Where these water drops come from? |
Conclusion : Water drops appear on the outer surface of the tumbler containing ice-cold water due to condensation of water vapour present in air.
The air around the tumbler contains water vapour in it. Where the water vapour present in air come in contact with the cold, outside surface of glass, they get cooled and condense to form tiny drops of liquid water.
Activity 4.
Aim : To show that the water appearing on the outer surface of the glass tumbler in Activity 3 is due to condensation of water vapour present in the air.
Material Required: A glass tumbler, water, ice-cubes, a small steel plate, a digital weighing balance.
Procedure :
- Take a glass tumbler half-filled with water containing a few ice cubes.
- Cover it with a small steel plate.
- Weight it on a digital weighing machine.
- Observe the reading on the balance and record the weight after every five minutes.
- Continue observing for 30 minutes.
Observations:
| Time | Mass of water |
| 0 min | 1 |
| 5 min | |
| 10 min | |
| 15 min | |
| 20 min | |
| 25 min | |
| 30 min |
There is an increase in the reading on the digital weighing machine.
Conclusion: The water collected outside the tumbler is only due to condensation.
To show that water is not seeping from the glass tumbler, we have to modify Activity 4 to find its answer.
There is an increase in the reading on the digital weighing machine.
Conclusion: The water collected outside the tumbler is only due to condensation.
To show that water is not seeping from the glass tumbler, we have to modify Activity 4 to find its answer.
1. Mark the water level on the glass tumbler with a permanent marker or a visible tape.
Observations :
Water level in the glass-tumbler does not go down but the extra water gets collected on the outer surface of the glass tumbler. Thus, this activity shows that water is not seeping from the glass tumbler and the extra water is getting collected because of condensation.
Activity 5.
Aim: To identify the properties of different states of water.
Materials Required : A container, ice cube, container of different shapes, clear surface.
Procedure:
- Put on ice-cube in one container and transter it to another container of different shape. Record your observations.
- Pour water from one container to another container of a different shape. Observe how water behaves compared to the ice cube and make a record.
- Pour water on a clear surface and how it spreads.
- When water gets converted into water vapour, how does this water vapour spread?
Observations:
| S.No. | Property | Ice (Solid State) | Water (Liquid State) | Water vapour (Gaseous State) |
| 1. | Shape | Definite shape | No definite shape | No definite shape |
| 2. | Ability to flow | Does not flow | flow | flow |
| 3. | Ability to spread | Does not spread | Spreads | Spreads |
Activity 6.
Aim : To complete the given diagram. Liquid, Freezes, Evaporates, Gas, Condess
Activity 7(a).
Aim : To investigate conditions that will affect how fast water will evaporate.
Materials Required: A small cap of bottle, water, a plate.
Procedure :
- Take water in a small cap of a bottle.
- Take the same amount of water in plate. The exposed area of water in the bottle cap and the plate is different.
- Keep both of them near each other.
- Record the time taken for the water to completely evaporate in each case.
Observations:
| Exposed area of water | Time taken for complete evaporation |
| Less (bottle cap) | 30 minutes |
| More (Plate) | 20 minutes |
Conclusion: When we spread out water on a plate its area exposed to air is larger. Therefore, evaporation is faster.
Activity 7(b).
Aim : To find other conditions which affect how fast water evuporates.
Materials Required: Water, Identical plates (two).
Observation : Condition that is kept the same. The exposed areas of water in the states are same.
| Condition that is changed | Time taken for complete evaporation |
| Sun-light area | 20 minutes |
| Shade area | 35 minutes |
Conclusion : The rate of evaporation increases with increase in temperature.
Activity 8.
Aim : To show the rate of evaporation increase with increase in temperature.
Materials Required : Two identical caps of two bottle, water.
Procedure:
- Take identical caps of two bottles.
- Pour equal amount of water in each of the cap.
- Place one of the cap in sunlight and keep the other in shade.
- Observe the two caps of bottles after every 15 minutes.
- Record the time taken for the water to completely evaporate in each case.
- You can also repeat this activity on a windy or a rainy day and record your observations.
Observations:
| Condition that is changed | Time taken for complete evaporation |
| (a) Sunlight | 35 minutes |
| (b) Shade | 60 minutes |
| (c) Windy | 40 minutes |
| (d) Non-windy | 65 minutes |
| (e) Rainy day | 75 minutes |
| (f) Dry day | 40 minutes |
Conclusion:
- Water evaporates faster from the cap in sunlight compared to the cap kept in shade.
- Water evaporates faster from the cap kept in a windy area compared to the cap kept in non-windy area.
- Water evaporates faster from the cap kept in a non-rainy area compared to the cap left in rainy area.
Activity 9.
Aim: To observe the cooling effect by making a simple and electricity-free model of pot-in-pot cooler.
Materials Required: Two earthen pots of different sizes, sand, water, a lid or wet jute sack.
Procedure :
- Take two earthen pots of different sizes.
- Fill the bottom of the longer pot with a layer of sand.
- Place the smaller pot into the centre of the larger one.
- Fill the gap between the pots with more sand.
- Pour water in the sand area.
- Place a lid or wet jute sack to cover the top of the smaller pot.
- Allow 4-5 hours for the mint pot-in-pot cooler to cool down. A pot-in-pot cooler is ready. In summers, Surahi is used to keep the water cold.
Activity 10.
Aim : To demonstrate the role of dust particles in the formation of clouds.
Materials Required : An empty discarded one litre plastic bottle, water burnt piece of newspaper.
Procedure:
- Take an empty discarded one litre plastic bottle. Pour about one cup of water into it.
- Close the lid tightly. Now quickly squeeze and release the bottle continuously for about 2-3 minutes. Observe the space above the water in the bottle.
- Repeat the same activity after adding a small burnt piece of newspaper into the water.
Observations: We observe some haziness (clouds) above the water in the bottle.
The burnt newspaper provides very small invisible dust particles around which water vapour condenses and forms clouds.
Activity 11.
Aim: To represent how water changes its state and movement.
Procedure: Observe the water cycle given in Fig. 7.
The water from the ocean and the Earth’s Surface evaporates into the atmosphere as vapour and and returns as rain, hail or snow, ultimately flows back to the oceans. The circulation of water is known as the water cycle.
The water cycle is powered by the heat of the Sun and the force of gravity. The heat of the Sun melts ice and evaporates water. The gravity makes the rain or snow fall to ground. It then makes the rivers and steams to flow from the mountains to the oceans.
Only a small portion (0.01%) of water available on the Earth is fit for use by plants, animals and human. Most of the water (97.4%) is in the ocean and it cannot be used directly. We use water for drinking and also for many other activities. The number of people using water is increasing with a rise in population. The increasing demand for water causes its shortage in many parts of the world. Hence, it is important to use water wisely and avoid wasting.