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Observation The contents turn bluish.

Activity Took a pinch of wheat flour and moisten it with water and add a few drops of iodine solution. Observation The contents turn bluish. Question Why it so happens?. Answer Wheat flour contains starch and starch gives blue colour with iodine.

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Observation The contents turn bluish.

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  1. ActivityTook a pinch of wheat flour and moisten it with water and add a few drops of iodine solution.

  2. ObservationThe contents turn bluish. Question Why it so happens?

  3. AnswerWheat flour contains starch and starch gives blue colour with iodine.

  4. Activity1. Prepare water extract of a pinch of a chemical compound in a beaker. 2. Took a small quantity of the extract and added to it freshly prepared ferrous sulphate solution. 3. Now added conc. H2SO4 by the sides of the test tube.

  5. ObservationsA dark brown ring is seen in the middle of the solution. Question What could be the nature of the compound used?

  6. AnswerIt is a ring test of Nitrate.

  7. Activity1. Put lime water solution in a test tube2. Blow air from the mouth through the solution with the help of a glass tube

  8. ObservationThe solution turn milky. Question 1. Give the chemical name of the substance contained in the test tube.2. State the reason of the contents of the tube turning milky.

  9. Answer1. The test tube contains Calcium hydroxide.2. When air from the mouth is blown in the lime water, the Calcium hydroxide gets converted into Calcium carbonate by reacting the Carbon dioxide of the air from the mouth. The solution of Calcium carbonate is milky.

  10. Activity1. Gently lower an egg into a large glass of water. It will sink.2. Remove the egg and put 10 table spoons of the salt in the water and dissolve it completely to make in the solution.3. Put the egg in the solution.

  11. Questions Reason out the observation and define the phenomenon involved. ObservationsIn the pure water the egg sinks whereas in the water with the salt, the egg floats.

  12. Answer1. The being denser than pure water sinks. On the other hand, the addition of the salt makes the water denser than the egg, so the egg floats.2. Density is the mass of a substance per unit volume i.e.d = M/V

  13. Activity1. Hold a postcard size paper between the thumb and the index finger in one hand.2. Place the thumb & index finger of the other hand close to the other end of paper such that it does not touch the paper.3. Release the paper and try to catch it with other hand. 4. Now ask your friend to catch the paper while you release it.

  14. ObservationsWhile you release the paper with one hand you can easily catch it with the other hand. However, your friend can not. Question Explain the reason.

  15. AnswerWhen the same person holding the paper tries to catch it, it gets caught because the brain sends the impulse to the motor nerve to act on the muscles.On the other hand when the person who is to catch the paper is different from the one who release it, the eyes of former (who is to catch) send the message through the eyes to the brain which in turn sends the impulse to the motor nerve to act to catch the paper. This takes longer time than in the first situation.

  16. Activity:Take a test tube and fill 3/4th of it with water.Hold the tube in an inclined position and heat the upper part of the water in it.

  17. Observation:The water at the upper level starts boiling. However, there is no difficulty in holding the tube from the lower end. Question: Why the lower end does not get hot?

  18. Answer:When water is heated even to the extent of boiling, it gets converted into steam that being lighter in weight, escapes out from the tube. So the water at the lower part of the tube remains unaffected by the heat

  19. ActivityTake tow eggs – one fresh/raw and other hard boiled.Give spin to both the eggs simultaneously on a horizontal plane surface.

  20. ObservationOne egg spins uniformly and the other vaguely. Question 1. Distinguish between the raw and the hard boiled egg. 2. Give basis for your inference.

  21. Answer1. The egg that spins well is hard boiled while the other that spins vaguely is the raw one.2. The raw egg does not spin well because the friction between the egg shell and the surface of the base gets impaired by the friction between the contents of the egg and the shell.

  22. Activity1. Take a small bucket filled half with water.2. Put the bucket in circular motion with at a fast speed.

  23. ObservationThe water from the bucket does not fall even when it is inverted at the top of the round. Question Why water does not fall?

  24. AnswerWater doesn’t fall because of the centrifugal force. It maintains the maximum distance between the object moving speedily in a circular path and the center of circle of rotation. The more the speed of rotation, the more will be the centrifugal force.

  25. Activity1. Take a cup and place a coin in it.2. Look at it and starts moving away from it till the coin becomes out of sight.3. Request some one to add water into the cup slowly till it is nearly filled.

  26. ObservationYou can again see the coin from the position from it was not visible earlier. Question What is the reason of reappearance of this coin?

  27. AnswerThe coin is visible in the cup because the light travels straight from the coin into your eyes but when you move away, the wall of he cup obstructs the path of light.When the cup is filled with water, the ray of light traveling through the medium of water gets refracted when it enters the medium of air. The refracted image of he coin is thus, visible.

  28. Activity1. Take a thick paper and make its pot and fill about half with water.2. Place it over a wire gauge on a tripod stand and heat it with flame.

  29. ObservationWater gets warm up without burning the paper. Question Why the paper does not burn.

  30. AnswerIn an uncovered pot one can warm water only up to the boiling point i.e. 100ºC. Water having great heat capacity, absorbs the papers’ extra heat and prevents it from warming more than 100ºC, i.e. to a point where it could burst into flame.

  31. ActivityTake a bar magnet near to the iron fillings.

  32. Observation:The magnet attracts the iron fillings. Question: Why does it attract?

  33. Answer:In the magnet the half field spins of the atoms give us the domain of a tiny magnet, in bar magnet, these tiny magnets are arranged in a particular order that attracts the iron fillings to make the filling in the same order

  34. ActivitySqueeze some lemon juice on a piece of chalk.

  35. ObservationFizzes appear on the chalk surface. Question Why does it so happen?

  36. AnswerFizzes appear due to production of gas.Calcium carbonate of chalk reacts with weak acid and produces CO2

  37. ActivityTake two bar magnets. Bring them together

  38. Observation:They either attract or repel each other. Question: Why it is so?

  39. Answer:Magnetic poles connect the magnets by their respective field lines. When the same pole come closer, the field lines repel each other that is why the like poles repel. While opposite poles take field lines from one pole to terminate to another pole. Therefore, they attract each other.

  40. ActivityTake a flask and cover its mouth with a balloon.Heat the flask.

  41. ObservationThe balloon inflates Question Why it inflates?

  42. AnswerWhen the flask is heated, the air inside it expands and becomes lighter and needs more space. It goes into the balloon which inflates.

  43. Activity1. Take two beakers of equal sizes.2. Pour cold water in the one and the hot water in the other.3. Put two drops of the dark ink in each beaker simultaneously.

  44. ObservationIn the beaker containing hot water in the ink dissolves readily than in the one having cold water. Question Reason out the observations and define the phenomenon behind this.

  45. AnswerThe reason behind this observation is the process of diffusion. It depends upon the concentration and nature of the solute and temperature. In the hot water due to high temperature, the kinetic energy of the solute molecules is more, thereby resulting in the fast dissolving of ink in hot water.Diffusion is the movement of the solute from higher conc. to lower conc.

  46. ActivityPut a stamp on the table and place a glass beaker containing water over it.Cover it with saucer.

  47. ObservationThe stamp disappears irrespective of the direction from where we try to see. Question Why does stamp disappear?

  48. AnswerThe principle of Refraction governs the phenomenon involved. The incident light while entering from the rarer to the denser medium bends towards the normal, and moves away from normal when it comes from denser to rarer medium. When we look from the side, the angles formed are such that the stamp becomes invisible.

  49. ActivityTook a glass of water. Pour a drop of honey from two different samples

  50. ObservationOne of the samples shows a fibrous streak of honey while the other dissolves without forming the honey thread. Question What inference is drawn?

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