Class 9 Science Chapter 2 MCQ

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

Decaying of wood and burning of wood are chemical changes, because in this processes, the chemical composition of wood is changed and the new substance are formed, which cannot be converted back into their original form. In Sawing of wood and hammering of a nail into a piece of wood, chemical composition of wood is not changed, therefore, option [C] is physical change. 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).

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.

Metals are good conductors of heat and electricity. This refers that metals allow heat and electricity to pass through them easily. Metals are generally good conductor of heat. Silver metal is the best conductor of heat. Gold and silver have the highest thermal conductivity. Copper and Aluminium metals are also very good conductors of heat.

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

In a true solution (like sugar solution), the solid particles are so small that they cannot scatter light rays falling on them. For example, if a beam of light (from a torch) is put on true solution (like sugar solution) kept in a beaker in a dark room, the path of light beam is invisible inside the solution when seen from the side. The beam of light can become visible only when the solid particles are big enough to reflect light falling on them. Since the particles of a true solution do not a scatter light.

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

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].

i) If the substance does not have a fixed melting point, boiling point, etc., it is a mixture. ii) If the substance has a fixed melting point, boiling point, etc., it is considered as a compound.