Class 9 Science Chapter 2 MCQ

Copper is a good conductor of electricity. It means that it offers very low electric resistance. Also, it is highly ductile due to which it can be drawn into very thin wires.

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).

Iodine dissolved in alcohol is called tincture of iodine.

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.

A pure substance is made up of only one kind of particles like elements. The composition of pure compounds is also same throughout.

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 chemical changes are permanent changes which are usually irreversible.

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.