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Is Matter Around Us Pure
Question
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Name and explain any five physical changes.

Answer

1. Change of physical state: Solids can be converted into liquid and then to a gas by heating or vice-versa.

2. Glowing of an electric bulb: When a bulb is switched on, its filament made of tungsten starts glowing. When the bulb is switched off, the bulb stops glowing and there is no change in its filament.

3. Dissolution of salts: When common salt is added to water, a solution is formed. When the solution is heated, water evaporates and white solid of common salt is left behind. This white solid has the same properties as the original substance.

4. Mixing of iron filings and sulphur: If the iron filings are separated from sulphur with the help of a magnet, the properties of the substances recovered are the same as the original substances, i.e., iron filings and sulphur.

5. Sublimation of naphthalene: When naphthalene is heated, it gets converted into vapours which are sublimed (condensed) into a white solid, which has the same properties as the original substance.

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Some More Questions From Is Matter Around Us Pure Chapter

Which separation techniques will you apply for the separation of the following?

Tea leaves from tea

Which separation techniques will you apply for the separation of the following?

Iron pins from sand.

Which separation techniques will you apply for the separation of the following?

Wheat grains from husk

Which separation techniques will you apply for the separation of the following?


Fine mud particles suspended in water.

Write the steps you would use for making tea. Use the words—solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

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


What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?

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.

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


Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?

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


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

What is the effect of change of temperature on the solubility of a salt?

Explain the following giving examples:

Saturated solution