SUMMATIVE ASSESSMENT A. VERY SHORT ANSWER QUESTIONS (VSAQ): 1. Give reasons for the following (a) School bells are made up of metal alloys. (b) Gold and silver are used for making Jewellery. (c) Silver is used for making contact points in electric switches. (d) Base of cooking utensils is coated with copper. 2. Zinc displaces copper from its aqueous solution whereas the reverse reaction is (e) Acidic food should not be stored in metal containers made up of copper and 3. Identify the most malleable, ductile and brittle substance out of the following: (iv) Silver (v) Sulphur. (0) Sodium (ii) Aluminium (iii) Gold 4. Identify the hard, soft and good conductor of heat and electricity from the follow () Iron (i) Potassium (ii) Sodium (iv) Copper (V) Silver (vi) Zinc SHORT ANSWER QUESTIONS (SAQ) : 1. Define malleability. Give an example. 2. What is meant by ductility ? Give an example. Name the least reactive and most reactive metal.
Answers
1) a) School bells are made of metals because metals are sonorous which means it produces they produces ringing sound when hit with hard object.
b) Platinum Gold and silver are used to make jewellery because of the following reasons. They are highly lustrous metals which are resistant to corrosion. They are highly malleable and ductile so can be transformed into any shape or design.
c) EM-S is a composite alloy of silver and tungsten produced by powder metallurgy, containing from 20 to 70 weight percent of silver. This is usually used for contact points of switches and circuit breakers filled with oil or SF6 gas.
d) COPPER IS A GOOD CONDUCTOR OF HEAT. IN COOKING UTENSILS SUCH METALS ARE USED WHO ARE GOOD CONDUCTORS OF HEAT, SO THAT, THE FOOD GETS COOKED FAST AND WITHIN SHORT TIME. AS COPPER IS A GOOD CONDUCTOR, IT IS USED AT THE BASE OF COOKING UTENSILS.