Class 9 Science Chapter 2 MCQ

A2B is a compound made up of two elements A and B in a fixed ratio. The properties of a compound (e.g. A2B) are entirely different from those of its constituent elements (e.g. A and B). The composition of a compound is fixed.

Here, all these statements are correct. Hence your answer will be option [D].

Iodine dissolved in alcohol is called tincture of iodine.

Ice and air are homogeneous in nature as their particles are not distinctly visible. A homogeneous mixture has a uniform composition throughout its mass. It has no visible boundaries of separation between its various constituents. Example – air, sugar solution, brass etc. A heterogeneous mixture does not have a uniform composition throughout its mass. It has visible boundaries of separation between its various constituents. Example – soil, wood, blood etc.

Actually, rusting of an article, made up of iron is called corrosion. Corrosion is a chemical change because rust is a chemical compound (hydrated iron oxide) which is totally different from element iron (Fe). Physical changes are those changes in which no new substances are formed. The substances do not change their identity and they can be easily returned to their original form by some physical processes. Example – melting of ice, glowing of an electric bulb, breaking of glass tumbler etc. On the other hand, chemical changes are those changes in which new substances are formed. The substances involved change their identity and they get converted into entirely new substances, which cannot be returned to their original form i.e. burning of paper, rusting of iron, burning of magnesium wire etc. Note: Dissolution is the process in which a solute is dissolved in a solvent to form solution.

Here, are all the statements are correct. Hence, your answer will be option [D].

A soap solution scatters a beam of light passing through it and renders its path visible, therefore, soap solution is a colloid (or colloidal solution).

The separation of a dissolved solids from a liquid can be done by a number of other methods such as evaporation, crystallization, distillation and chromatography etc.

Here, are all the statements are correct. Hence, your answer will be option [D].

The process in option [B] is a chemical change because rusting causes formation of a new compound. Other statements are examples of physical changes where no new compounds are formed. In the process mentioned in other statements, original form of iron can be obtained back from moulded forms.