Atoms And Molecules (Solved)
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Q. 121. How many elements are known so far ?
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Q. 122. State the numbers of non-metals. How many of them are solid, liquid and gases ?
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Q.123. State the examples where the property-malleability and ductility of metals are used in daily life.
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Q. 124.Give example of a metal which :
(i) is a liquid at room temperature,
(ii) Can be cut easily with knife,
(iii) is the best conductor of heat ,
(iv) is the poorest conductor of heat.
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Q.125. State the metals used for the following purposes :
(a) Household utensils and factory equipments,
(b) Jewelries,
(c) Packaging of food stuff,
(d) Atomic energy and space research,
(e) Transport of electricity.
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Q. 126. From the following list select the metals and non-metals. Also write their property on which they are classified :
(i) Aluminium,
(ii) Carbon,
(iii) Chlorine,
(iv) Helium,
(v) Silver,
(vi) Sulphur,
(vii) Sodium.
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Q. 127. State the properties of sodium in which it does not show the properties of metal.
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Q.128. Write those properties of carbon which are not expected in non-metals.
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Q.129. Differentiate between metals and non-metals.
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Q.130. State the characteristics of a compound.
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Q. 131. What difference is observed when a mixture of iron filings and sulphur
(i) is crushed hard ?
(ii) is heated red hot ?
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Q. 132.Which separation techniques will you apply for the separation of the following :
(i) Sodium chloride from its solution in water.
(ii) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(iii) Small pieces of metal in the engine oil of a car.
(iv) Different pigments from an extract of flower petal.
(v) Butter from curd.
(vi) Oil from water.
(vii) Tea leaves from tea.
(viii) Iron pins from sand.
(ix) Wheat grains from husk.
(x) Fine mud particles suspended in water.
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Q. 133. Write the steps you would use for making tea. Use the words – solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
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Q. 134. Pragya, tested the solubility of three different substances at different temperatures and collected the data as given below ( results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution ).
| Substance dissolved | Temperature in K | ||||
| 283 | 293 | 313 | 333 | 353 | |
| Potassium Nitrate | 21 | 32 | 62 | 106 | 107 |
| Sodium Chloride | 36 | 36 | 36 | 37 | 37 |
| Potassium Chloride | 35 | 35 | 40 | 46 | 54 |
| Ammonium Chloride | 24 | 37 | 41 | 55 | 66 |
(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 gram of water at 313 K.
(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools ? Explain.
(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature ?
(d) What is the effect of change of temperature on the solubility of a salt ?
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Q. 135. Explain the following giving examples :
(a) Saturated Solution,
(b)Pure Substance,
(c) Colloid,
(d) Suspension.
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Q. 136. Classify each of the following as homogeneous or heterogeneous mixture :
soda water, wood, air, soil, vinegar, filtered tea.
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Q. 137. How would you confirm that a colourless liquid given to you is pure water ?
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Q. 138. Which of the following materials fall in the category of a “pure substance” ?
(a) Ice
(b)Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood (i) Air.
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Q. 139. Identify the solutions among the following mixture :
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water.
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Q.140. Which of the following will show “Tyndall effect” ?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution.
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Q. 141. Classify the following into elements, compounds and mixtures :
(a) Sodium
(b) Soil
(c) Sugar Solution
(d) Silver
(e) Calcium Carbonate
(f) Tin
(g) Silicon
(h) Coal
(i) Air
(j) Soap
(k) Methane
(l) Carbon Dioxide
(m) Blood.
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Q. 142. Which of the following are chemical changes ? :
(a) Growth of plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d)Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of candle.
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