Q.1. Name the process by which components colloidal solution separated?
Q. 2. Identify solute and solvent
Ans: Tincture of iodine: Iodine (solute) and Alcohol (solvent)
Aerated drink: CO2 (solute) and Water (solvent)
Q.3. State the principal of each:
Ans: Separation using separating funnel: Immiscible liquids separates out in layer depending on their densities
Centrifugation: the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.
Distillation: Two miscible liquids that boil without decomposition and have sufficient difference in their boiling points.
Chromatography: solutes have difference in solubility that dissolve in the same solvent.
Q.4. Why does crystallisation technique is better than simple evaporation technique?
Ans: Crystallisation technique is better than simple evaporation technique as –
(i) some solids decompose or some, like sugar, may get charred on heating to dryness.
(ii) some impurities may remain dissolved in the solution even after filtration. On evaporation these contaminate the solid.
Q.5. Give reason for: Naphthalene balls disappear with time without leaving any solid residue.
Ans: Naphthalene balls changes directly from solid to gaseous state on heating.
Q.6. Give two reasons for supporting that water is a compound and not a mixture.
Ans: water is a compound as : Water has uniform composition of hydrogen and oxygen in 2:1. Hydrogen and oxygen cannot be separated by physical method.
Q.7. Give two reasons for supporting that air is a mixture.
Ans: air is a mixture as: Air has different composition of gases. its constituent gases can be separated by physical method.
Q.8. What is metalloid. Give two examples
Ans: Elements having properties of both metal and non metals are called metelloide eg. boron, silicon, germanium etc