Class 6 Science Chapter 8 Extra Questions A Journey through States of Water
Class 6 Science Chapter 8 A Journey through States of Water Important Extra Questions and Answers
A Journey through States of Water Class 6 Extra Questions Very Short Answer Type
Question 1.
To which physical state of matter, do the following statement apply?
(i) Incompressible, no fixed Shape
(ii) Compressible, no definite volume.
Answer:
(i) Liquid (ii) Gas
Question 2.
Give one common characteristic between solids and liquids?
Answer:
Both have a definite volume
Question 3.
Why a wooden table should be called a solid?
Answer:
It has a definite shape, distinct boundaries and definite volume.
Question 4.
Why oxygen should be called a gas?
Answer:
It has neither a fixed shape nor a fixed volume.
Question 5.
Why water should be called a liquid?
Answer:
It has a fixed volume but not a fixed shape.
Question 6.
How the rate of evaporation of a liquid is affected with increases in temperature of the liquid?
Answer:
Rate of evaporation increases with rise in temperature.
Question 7.
State one difference between gas ans vapour?
Answer:
Gas is stable state of matter whereas vapour is the unstable state.
Question 8.
What is the physical state of water at 253 K under one atmospheric pressure?
Answer:
Solid.
Question 9.
What is the physical state of water at 298 K under one atmospheric pressure?
Answer:
Liquid.
Question 10.
Can materials exists in all the three states?
Answer:
Yes, materials can exists in all the three states under different conditions of the temperature and pressure.
A Journey through States of Water Class 6 Extra Questions Short Answer Type
Question 1.
Why do wet clothes dry quickly in the Sun than in the shade?
Answer:
The temperature of the sunny area is higher than in the shade and evaporation takes places at a faster rate at high temperature. So, wet clothes dry quickly in the sun.
Question 2.
Why do we feel comfortable under a fan when we are perspiring?
Answer:
The sweat is readily evaporated from the body by the air. As a result, we feel comfortable under a fan.
Question 3.
A rubber band can change its shape on stretching. Will you classify it as solid or not?
Answer:
Rubber band changes shape under force and regains the shape when the force is removed. So, it is classified as a solid.
Question 4.
Gases completely fill the container in which they are kept. Give reasons.
Answer:
In the gaseous state, particles move freely and have greater space between them. So, they occupy the entire space available. Hence, gases completely fill the container in which they are kept.
Question 5.
Give two reasons to justify water is a liquid at room temperature.
Answer:
- At room temperature, water has fixed shape because it takes shape of the container which in which is kept.
- It is compressible.
Question 6.
To clean their spectacles, people often breathe out on glasses to make them wet. Why glasses become wet?
Answer:
The breathe out gases contain water vapour. The water vapour condenses at spectacles, so glass becomes wet and with the help of small amount of water, it is easy to clean the spectacles.
Question 7.
Why do people sprinkle water on the roof after a hot summer day?
Answer:
Water sprinkled on the roof evaporate by taking the large heat from the ground. This makes the place cool and comfortable.
Question 8.
Write any two factors affecting water table.
Answer:
Water table is affected by the following factors:
- Average rainfall in that area.
- Pumping out of the ground water.
Question 9.
Why are gases compressible but not liquids?
Answer:
Gases are compressible because the intermolecular space is very large in glass whereas liquid are not compressible because in liquids, the intermolecules space is less.
Question 10.
Why does a desert cooler cool better on a hot dry day?
Answer:
A hot dry day means that temperature of the atmosphere is high and humidity of air is low. Both these factors increase the rate of evaporation and thus enormous cooling is produced.
Question 11.
A gas fills completely the container in which it is kept. Why?
Answer:
The particles of a gas are constantly moving in all the directions with different speeds. Therefore, they do not have a fixed volume and hence completely fill the container is which they are kept.
Question 12.
How are clouds formed?
Answer:
The water present on the earth evaporates due to heating by the Sun. The water vapour in the air condenses to form tiny droplets of water at high altitude, which appears as clouds. Thus clouds are formed by the condensation of water vapour present in air at high altitude.
Question 13.
Take out the cooled bottle of water from refrigerator and keep it on a table. After sometime you notice a puddle of water around it. Why?
Answer:
The cooled water bottle has very cold exposed surface. Due to cool surface there is condensation of water vapour from air on the surface of water bottle because water vapour is present in atmosphere. The condensed water molecules spread around the bottle. So a puddle of water is noticed after sometime.
Question 14.
Why do the doctors advise to put strips of wet cloth on the forehead of a person having high fever?
Answer:
When a person has fever, his body temperature becomes more than the normal body temperature. If we put strips of wet cloth on the forehead of a person suffering form high fever, the water evaporates taking heat from the body. Thus, moist strips will lower his body temperature.
Question 15.
How does the water kept in an earthen pot (matka) become cool during summer?
Answer:
Due to small pores present in the walls of earthen pot, the water oozes out slowly. At it comes out on the outer surface of matka it evaporates. The heat needed for evaporation is taken from the water kept in the earthen pot. As a result, water kept in the earthen pot becomes cold.
Question 16.
We can easily move our hand in air but not through any solid materials. Give reasons?
Answer:
(i) Intermolecular forces between constituent particles are negligible in air, whereas these are very strong in solids.
(ii) The particles in air have sufficient freedom of movement whereas in solid they have high rigidity.
(iii) The inter molecular space between constituent particles is very large in air but is negligible in solids.
Thus, we can easily move our hand in air but not through any solid material.
Question 17.
Why the gases are highly compressible as compared to solids and liquids? Give two examples where we fill large volumes of gas in small cylinders.
Answer:
The gases are highly compressible as compared to solid and liquids due to low intermolecular forces of attraction between the particles of gases. Examples where we fill large volumes of gases in small cylinders :
- The liquified Petroleum Gas (LPG).
- Compressed Natural Gas (CNG).
Question 7.
Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Answer:
When hot tea or milk is taken in a cup, the surface area of the liquid in the cup is small. Therefore, evaporation occurs slowly and hence the liquid in the cup remains hot for a sufficient long time. When hot tea or milk is placed in a saucer, the surface area of the liquid increases. As a result, evaporation occurs faster and the tea or milk becomes little cooler more quickly. So, we are able to sip hot tea or milk faster from a saucer than from a cup.
Question 8.
What type of clothes should we wear in summer?
Answer:
In summer, we perspire more. Therefore, to keep our body cool, we must wear cotton clothes. Since, cotton clothes are good absorber of water, they absorb the sweat quickly and expose it to the atmosphere for easy evaporation. Since, evaporation produces cooling, therefore, cotton clothes help us in keeping our body cool.
Question 9.
Suppose you want to dry your school uniform quickly. Would spreading it near an heater help you? If yes, how?
Answer:
Yes, to dry the school uniform quickly, uniform is spread near a heater, because evaporation is rapid at higher temperature. Higher the temperature, faster is the rate of evaporation. So, the uniform is dried up quickly.
Question 10.
Explain how the rate of evaporation of a liquid is affected with
(a) Increase in temperature of the liquid.
(b) Decrease in exposed surface area.
(c) Increase in moisture in the surrounding air.
Answer:
(a) Rate of evaporation increases with rise in temperature.
(b) Evaporation is less when exposed surface area decreases.
(c) Less evaporation if moisture content is high in the air.
Question 11.
Name the factors on which evaporation depends?
Answer:
Evaporation depends upon:
- The area of the exposed surface.
- The nature of the liquid.
- The temperature of the liquid.
- The blowing of air over the liquid surface.
- The dryness of the air.
Question 12.
Perspiration keeps our body cold. Give reason?
Answer:
On a hot summer day or after doing heavy exercise, the temperature of our body tends to rise. Due to increase in temperature, our body gives out sweat. When sweat evaporates, it absorbs heat from our body. By losing heat, our body feels cool.
A Journey through States of Water Class 6 Extra Questions Long Answer Type
Question 1.
Discuss the various factors which affect the rate of evaporation.
Answer:
Factors affecting the rate of evaporation :
- Surface area: The rate of evaporation increases with increase in surface area.
- Temperature: The rate of evaporation increases with increase in temperature.
- Humidity : The rate of evaporation decreases with increase in humidity.
- Wind speed : The rate of evaporation increases with increase in wind speed.
- Nature of the liquid : The volatile compounds evaporates faster than less volatile liquids.
Question 2.
Describe water cycle in nature.
Answer:
(i) Heat from the sun evaporates water from rivers, lakes, ponds, oceans and soil to form water vapour. This water vapour goes into the air.
(ii) The air containing water vapour is heated by the Sun. Hot air, being lighter, rises in the sky. The higher the air goes, the cooler it becomes. After reaching a certain height, the air becomes very cold and water varpour in the air condenses into extremely small water droplets. These droplets together form clouds.
As the clouds rise higher, more vapour condenses and collects on the tiny water droplets. The water droplets grow bigger, become heavy and ultimately fall downward as rain.
If the temperature close to the land is 0^{\circ} \mathrm{C} (freezing point) or less, the water droplets in the clods turn into ice. This gives to snowfall.
(iii) Water formed from the melting of snow and some of the rain water flows into the rivers and finally goes into 158 oceans. The rain water also fills the lakes and ponds, and gets absorbed by the soil. Some of the rain water seeps through the soil. In this way, water which was taken from the earth, returns to the earth and the water cycle is completed.
Question 3.
A material X can exist in three physical states : solid, liquid and gas. No living thing on earth can exist in the absence of this material. This material falls from the clouds in the form of Y. Lack of Y for long periods in an area may cause Z whereas excess of Y may cause A .
(a) What are (i) X, (ii) Y (iii) Z and (iv) A.
(b) What is the solid state of X known as?
Answer:
(a)
- X is water.
- Y is rain.
- Z is drought.
- A is flood.
(b) Ice or Snow.
Question 4.
With the help of an activity show that gases are easily compressible than liquids and solids.
Answer:
Activity
- Take three 100 ml syringes and close the nozzles by rubber cork.
- In one syringe, piece of chalk powder is filled up, in the second water while the third one is left as it is.
- Now all these syringes are pressed by their pistons.
Observations : The piston was easily pushed in the syringe which was filled up with air but not in other syringes having water and chalk powder.
Conclusion : Gases are highly compressible than solids and liquds.
Question 5.
Why surgeons often spray some ether on skin before performing minor surgery?
Answer:
Surgeons spray ether on a portion of skin before performing minor surgery. The reason being that ether has very low boiling point. Therefore, it evaporates quite rapidly.
The heat need for evaporation is taken from the skin. As a result, the temperature of the skin becomes so low that it almost become numb. Due to this numbness, the patient does not feel much pain when minor cut is made in the skin in order to perform surgery.
A Journey through States of Water Class 6 Picture Based Questions
I. Observe the figure and answer the following questions :
Question 1.
What does the figure show ?
(a) Steel plate with a tablespoon of water.
(b) A plate with liquid.
(c) A steel plate.
(d) None of these.
Answer:
(a) Steel plate with a tablespoon of water.
Question 2.
Which phenomenon occurs during drying of wet clothes ?
(a) Condensation.
(b) Evaporation.
(c) Bathing.
(d) None of these.
Answer:
(b) Evaporation.
Question 3.
If water does not seep through the steel plate then where has the water gone?
Answer:
The water gets converted into gaseous state, called water vapour.
Question 4.
What is evaporation?
Answer:
The phenomenon of change of a liquid into vapours of any temperature below its boiling point is called evaporation.
II. Observe the figure and answer the following questions :
Question 1.
What does the figure show ?
(a) Evaporation of water in sunlight.
(b) Evaporation of water in shade.
(c) Both (a) and (b).
(d) None of these.
Answer:
(c) Both (a) and (b).
Question 2.
As humidity in air increases-
(a) Rate of evaporation decreases.
(b) Rate of evaporation.
(c) Rate of evaporation remains constant.
(d) None of these.
Answer:
(c) Rate of evaporation remains constant.
Question 3.
How does surface area affect the rate of evaporation?
Answer:
As surface area increases, more number of particles get converted into vapours and rate of evaporation increases.
Question 4.
How does temperature affect the rate of vaporisation?
Answer:
With increase in temperature kinetic energy of the particles of liquid also increases and rate of evaporation increases.
A Journey through States of Water Class 6 Case Based Questions
I. Water vapour (gaseous state) exhibits a property of spreading out in the entire available space. Gases do not possess fixed shape. Water vapour exists even at room temperature, though it is invisible to us. It is present during processes like drying of clothes or mopping of floors contribute to the water vapour in the air around us.
Question 1.
Give the common characteristic between liquids and gases.
(a) Both are gases.
(b)Both are fluids.
(c) Both are solid.
(d) Both are liquid.
Answer:
(b) Both are fluids.
Question 2.
When water vapours present in air come in contact with the cold surface of glass of water.
(a) It loses heat.
(b) Changes into liquid state in the form of water droplets.
(c) Both (a) and (b).
(d) None of these
Answer:
(c) Both (a) and (b).
Question 3.
State one difference between gas and vapour.
Answer:
Gas is stable state of matter whereas vapour is its unstable state.
Question 4.
A small volume of water in a kettle can fill a kitchen with steam. Explain why?
Answer:
The liquid form of water in converts into gaseous form in steam. Its particles move rapidly in all the directions and fill the kitchen as gases completely fills the container.
II. It is common observation that clothes dry faster on a hot sunny day. Do clothes dry faster or slower on a windy day? It is once against a common observation that clothes dry faster on a windy day. With the increase in the movement of air, water evaporates faster.
Question 1.
The process of conversion of water into its vapour state is called
(a) Evaporation.
(b) Boiling.
(c) Malting.
(d) None of these
Answer:
(a) Evaporation.
Question 2.
With increase in temperature :
(b) Kinetic energy of the particles of liquid also increases.
(b) Rate of evaporation increases.
(c) Both (a) and (b).
(d) None of these
Answer:
(c) Both (a) and (b).
Question 3.
How does increase in the speed of wind affect the rate of evaporation ?
Answer:
With increase in wind speed, the particles of water move away with the wind thereby decreasing the water vapours in the surrounding. As a result, the rate of evaporation increases.
Question 4.
In hot and humid weather, why we usually sit under the fan ?
Answer:
The fan increases the wind speed around us thereby increasing the rate of evaporation and making us feel more comfortable.