Is Matter Around Us Pure?

Topics in this chapter

• Matter Classification and Properties
• Elements, Compounds, and Pure Substances
• Homogeneous and Heterogeneous Mixtures
• Solutions, Solubility, and Concentration
• Colloids, Suspensions, and Tyndall Effect
• Separation Techniques for Mixtures
• Physical and Chemical Changes

Cheat sheet

Practice questions

1. Question 1Q-3409E3

   Which of the following materials falls into the category of a pure substance according to the classification of matter in chemistry?

   1. A.Sea water
   2. B.Ice
   3. C.Air
   4. D.Soil
   See the answer and solution
2. Question 2Q-23AD14

   During an experiment, a student heats a mixture of iron filings and sulphur powder strongly in a china dish. Which of the following observations correctly describes the product formed?

   1. A.A heterogeneous mixture is formed, and the components can be easily separated using a magnet.
   2. B.A homogeneous mixture is formed with no chemical reaction taking place.
   3. C.A compound is formed with properties different from both iron and sulphur, and it does not show magnetism.
   4. D.The iron filings melt completely and mix physically with sulphur without any energy change.
   See the answer and solution
3. Question 3Q-213C67

   A student wants to separate a mixture of two miscible liquids, acetone and water, whose boiling points differ by more than $25^\circ\text{C}$. Which standard laboratory technique should be used?

   1. A.Simple distillation
   2. B.Fractional distillation
   3. C.Centrifugation
   4. D.Sublimation
   See the answer and solution
4. Question 4Q-024A19

   Why does a true solution not scatter a beam of light passing through it (i.e., why does it not show the Tyndall effect)?

   1. A.Because the solute particles are larger than $100\text{ nm}$ in diameter.
   2. B.Because the solute particles are extremely small, having a diameter less than $1\text{ nm}$.
   3. C.Because the solute particles undergo Brownian motion constantly.
   4. D.Because a true solution is always coloured, which absorbs the light completely.
   See the answer and solution
5. Question 5Q-C2D2B5

   Calculate the concentration in terms of mass by mass percentage of a solution containing $40\text{ g}$ of common salt dissolved in $320\text{ g}$ of water.

   1. A.11.1%
   2. B.12.5%
   3. C.10.0%
   4. D.12.0%
   See the answer and solution