Also read: Chapter 1 Class 6 DAV Our Environment Chapter Introduction | Easy Notes and Summary
Chapter 2: DAV Class 6 Science Chapter 2 Food Solutions – Detailed Answers to Questions 1 to 6
A. Fill in the blanks.
- The process of grouping objects with similar properties is called classification.
- Anything that occupies space and has mass is called matter.
- In the gaseous state of matter, the constituent particles have very little hold on one another.
- Light does not pass through a blackboard as it is an opaque object.
- Smell of a perfume reaches us by the process of diffusion.
B. Write True or False for the following statements.
- Air is a man-made material. — False
- A thin polythene sheet is transparent. — True
- Pebbles float on water. — False
- Diffusion is the mixing of the particles of two materials on their own. — True
- Oxygen gas is slightly soluble in water. — True
C. Tick (✓) the correct option.
1. The state/states of matter, that have both a fixed shape and a definite volume, is/are—
✅ solids only
2. Your book is made up of matter, because it—
✅ occupies space and has some mass.
3. Which of the following is an opaque material?
✅ a piece of wood
4. In which of the following cases would diffusion be the fastest?
✅ gas in another gas.
5. Which of the following is insoluble in water?
✅ mustard oil
D. Answer the following questions in brief.
1. Define the following:
(a) Natural materials
Materials that are obtained directly from nature are called natural materials.
Examples: wood, cotton, water and air.
(b) Transparent materials
Materials through which light can pass easily and objects can be seen clearly are called transparent materials.
Examples: clear glass, clean water and air.
2. Name any three materials that are (i) transparent (ii) opaque in nature.
(i) Transparent materials:
- Air
- Clean water
- Clear glass
(ii) Opaque materials:
- Wood
- Iron
- Cardboard
3. Which state of matter (i) can (ii) cannot easily change its shape and volume? Why?
(i) The gaseous state of matter can easily change its shape and volume.
This is because the particles in gases are very loosely packed and move freely.
(ii) The solid state of matter cannot easily change its shape and volume.
This is because the particles in solids are tightly packed and have a strong force of attraction between them.
4. Why do materials diffuse into each other?
Materials diffuse into each other because their particles are continuously moving and have spaces between them. Due to this movement, the particles mix on their own.
5. Define the term ‘solubility’. How does it change on increasing the temperature of water?
Solubility is the maximum amount of a substance that can dissolve in a given amount of water at a particular temperature.
On increasing the temperature of water, the solubility of most solids increases. This means more substance can dissolve in hot water than in cold water.
6. Name three materials that are (i) soluble (ii) insoluble in water.
(i) Soluble materials:
- Sugar
- Common salt
- Alum
(ii) Insoluble materials:
- Sand
- Chalk powder
- Mustard oil
E. Answer the following questions.
1. Why do solids have a fixed shape and a definite volume?
Solids have a fixed shape and a definite volume because the particles in a solid are very closely packed together. There is a strong force of attraction between these particles, so they cannot move freely from one place to another. They can only vibrate at their fixed positions. Due to this, solids keep their own shape and volume.
For example, a book, a table and a stone always remain in the same shape unless force is applied to them.
2. Briefly describe an activity to show that pure water is a transparent liquid.
Activity:
Take a clean glass tumbler and fill it with pure water. Place the tumbler in front of a book or any object. Look through the water carefully.
Observation:
The letters of the book or the object behind the tumbler can be seen clearly through the water.
Conclusion:
This shows that pure water allows light to pass through it. Therefore, pure water is a transparent liquid.
3. Describe an activity to show that a solid can diffuse slowly into a liquid.
Activity:
Take a beaker filled with water. Slowly add a few crystals of potassium permanganate or copper sulphate into it. Do not stir the water and leave the beaker undisturbed for some time.
Observation:
After some time, the colour of the crystals starts spreading slowly throughout the water. Gradually, the whole water becomes coloured.
Conclusion:
This happens because the particles of the solid move and mix with the particles of water on their own. This shows that a solid can diffuse slowly into a liquid.
4. What is a ‘saturated solution’? How can one prepare a saturated solution of common salt in water?
A saturated solution is a solution in which no more solute can dissolve at a particular temperature.
Preparation of a saturated solution of common salt:
- Take some water in a beaker or glass.
- Add a small amount of common salt and stir it well.
- Keep adding more salt little by little while stirring continuously.
- After some time, no more salt dissolves and the extra salt settles at the bottom.
Conclusion:
At this stage, the solution becomes a saturated solution of common salt in water.
5. Suggest one activity to show the effect of temperature on the solubility of a solid in water.
Activity:
Take two beakers containing equal amounts of water. Keep one beaker with cold water and the other with hot water. Add one spoon of sugar to each beaker and stir them.
Continue adding sugar spoon by spoon into both beakers.
Observation:
More sugar dissolves in hot water than in cold water.
Conclusion:
This activity shows that the solubility of most solids increases when the temperature of water increases.