You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?
No, this changes cannot be reversed. If a toy is broken accidently than actually fixing it. After fixing, it will not be in the same condition as it was before. So this change cannot be reversed.
A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilised. Can the change in POP be reversed?
A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
A drawing sheet changes when you draw a picture on it. Can you reverse this change?
To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Give examples to explain the difference between changes that can or cannot be reversed.
Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.
S.No. | Change | Can be reversed (Yes/ No) |
---|---|---|
1 | The sawing of a piece of wood | |
2 | The melting of ice candy | |
3 | Dissolving sugar in water | |
4 | The cooking of food | |
5 | The ripening of a mango | |
6 | Souring of milk |
(a) Which kind of garbage is not converted into compost by the redworms?
(b) Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
Do you find that all living beings need the same kind of food?
Name the major nutrients in our food.
Classify the following fibres as natural or synthetic:
nylon, wool, cotton, silk, polyester, jute
Name five objects which can be made from wood.
Why do we need to separate different components of a mixture? Give two examples.
Correct the following statements and rewrite them in your notebook.
(a) Stem absorbs water and minerals from the soil.
(b) Leaves hold the plant upright.
(c) Roots conduct water to the leaves.
(d) The number of petals and sepals in a flower is always equal.
(e) If the sepals of a flower are joined together, its petals are also joined together.
(f) If the petals of a flower are joined together, then the pistil is joined to the petal.
Fill in the blanks:
(a) Joints of the bones help in the ——————— of the body.
(b) A combination of bones and cartilages forms the _______ of the body.
(c) The bones at the elbow are joined by a ______________________ joint.
(d) The contraction of the _____________ pulls the bones during movement.
What is a habitat?
What is winnowing? Where is it used?
Name five objects which can be made from wood.
How will you prove that air supports burning?
Which gas in the atmosphere is essential for respiration?
What is the composition of air?
Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?
Which of the things in the following list are nonliving?
Plough, Mushroom, Sewing machine, Radio, Boat, Water hyacinth, Earthworm
Fill up the blanks
(a) The method of separating seeds of paddy from its stalks is called ___________.
(b) When milk, cooled after boiling, is poured onto a piece of cloth the cream (malai) is left behind on it. This process of separating cream from milk is an example of ___________.
(c) Salt is obtained from seawater by the process of ___________.
(d) Impurities settled at the bottom when muddy water was kept overnight in a bucket. The clear water was then poured off from the top. The process of separation used in this example is called ___________.
Using the "conduction tester" on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.
True or false?
(a) A mixture of milk and water can be separated by filtration.
(b) A mixture of powdered salt and sugar can be separated by the process of winnowing. (c) Separation of sugar from tea can be done with filtration.
(d) Grain and husk can be separated with the process of decantation.