Question 4 : Birds can fly due to presence of air. State True or False.

Question 5 : Moving air makes it possible to fly a kite. State True or False.

Question 7 : Make a sentence using the given set of words. Respiration, dissolved, animals, air, aquatic

Question 8 : Plants produce oxygen during the process of making their own food. State True or False.

Question 10 : Which of the following components of air is present in the largest amount in the atmosphere?

Question 11 : Fill in the blanks: A weather cock shows the ______ in which the air is moving at that place.

Question 12 : Fill in the blanks. The components of air which are harmful to living beings are ____.

Question 13 : Air helps in the movements of sailing yachts and glider but plays no role in the flight of birds and aeroplanes. State True or False.

Question 14 : Boojho took an empty plastic bottle, turned it upside down and dipped its open mouth into a bucket filled with water. He then tilted the bottle slightly and made the following observations. (i) Bubbles of air came out from the bottle. (ii) Some water entered the bottle. (iii) Nitrogen gas came out in the form of bubbles and oxygen got dissolved in water. (iv) No bubbles formed, only water entered the bottle. Which observations is/are correct?

Question 15 : Fill in the blanks: Air is a ______ of some gases.

Question 16 : Biogas is made by cow dung , can we get cow dung again ?

Question 17 : A process in which an object becomes smaller or shrinks is called ?

Question 19 : 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 occured in the cement, could be reversed?

Question 21 : A process in which a solid melts to become a liquid on heating is called ?

Question 22 : Evaporation is the process of liquid turning into vapour. TRUE or FALSE ?

Question 23 : Paheli mixed flour and water and (i) made a dough, (ii) rolled the dough to make a chapati, (iii) baked the chapati on a pan, (iv) dried the chapati and ground it in a grinder to make powder. Identify all the changes (i) to (iv) as the changes that cannot be reversed.

Question 25 : Take some dough and make a ball. Try to roll out a roti. Can this change be reversed ?

Question 26 : While lighting a candle, Paheli observed the following changes (i)Wax was melting. (ii) Candle was burning. (iii) Size of the candle was reducing. (iv) Melted wax was getting solidified. Of the above, the changes that can be reversed are ---

Question 27 : A straight string is curled , can we get straight string again ?

Question 28 : To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?

Question 30 : Paheli had bought a new bottle of pickle from the market. She tried to open the metal cap to taste it but could not do so. She then took a bowl of hot water and immersed the upper end of the bottle in it for five minutes. She could easily open the bottle now. Can you give the reason for this?

Question 31 : A person makes a mixture of dry sand with sawdust or powdered dry leaves and keeps this mixture on a plate or a newspaper. Next, he looks at this mixture carefully. Would it be possible to separate the components by handpicking?

Question 32 : Paheli faced a problem while recovering salt mixed with sand. She has mixed a packet of salt in a small amount of sand. She used decantation or filtration and condensation process for recovering salt. But, she found, that she could recover only a small part of the salt that she had taken. What could have gone wrong?

Question 33 : Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. In which case would it be possible to dissolve more sugar?

Question 34 : A person adds two spoons of salt to water in a beaker and stirs it well. Can the person see any salt in the beaker, after stirring?

Question 35 : Why do we need to separate different components of a mixture?

Question 36 : Four mixtures are given below: (i) Kidney beans and chickpeas (ii) Pulses and rice (iii) Rice flakes and corn (iv) Potato wafers and biscuits . Which of these can be separated by the method of winnowing?

Question 37 : Read the story 'WISE FARMER' and choose the correct option to complete the story. He harvested the crops and left it under the ___________ to dry the stalks.

Question 38 : Fill in the blanks with appropriate words: Small pieces of stone can be removed from rice by _________.

Question 39 : A Person brings a sieve and a small quantity of flour from home, to the class. He then sieves the flour to separate any impurities in it. Now, he makes a fine powder of chalk pieces and mixes it with the flour. Can he separate the flour and the powdered chalk by sieving?

Question 40 : Read the story 'WISE FARMER' and choose the correct option to complete the story. To separate the seeds from the bundles of the stalk he ________ them.

Question 41 : A person mixes some soil to water in a glass and lets it stand for half an hour. Some soil settles at the bottom of water. Now, he slightly tilts the glass without disturbing the water and lets the water from the top flow into another glass as shown in the figure. What will you call this process?

Question 42 : Write the method of separation of the following pair of compounds: Rice flour mixed with kidney beans

Question 43 : Fill in the blank: 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 ___________.

Question 44 : 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 _______ .

Question 45 : A person needs to separate salt and water from the decanted liquid. So, he transfers this liquid to a kettle and close its lid. Then, he heats the kettle for some time and steam comes out. Now, he takes a metal plate with some ice on it and holds the plate just above the spout of the kettle. What will he observe?

Question 46 : State True or False: Separation of sugar from tea can be done with filtration.

Question 47 : Fill in the blank: Salt is obtained from seawater by the process of ___________.

Question 49 : 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 ______

Question 50 : State true or false. A mixture of wheat grains and wheat flour can be separated by sieving.