· A bad egg floats in water because the up-thrust produced on account of displaced water by the immersed portion of the bad egg is greater than the weight of the egg.
· A copper vessel left in the air for a long time turns green. This is due to the formation of copper carbonate when copper reacts with carbon dioxide and moisture present in the air.
· A lightning conductor is fixed to tall buildings to protect them from the destructive effects of the lightning.
· A man weigh more at the poles than at the equator because the polar radius of the Earth is less than the equatorial radius .Hence the gravitational pull is more at the poles than at the equator.
· A perspiring man feels relief when air floats by his side because the flow of air increases the rate of evaporation of perspiration from the body.
· A sliced apple, when exposed to air, turns brown after some time as it contains iron which gets oxidised and gives the fruit a brownish colour.
· A small space is left between each set of two rails of railway line to allow for their expansion in summer.
· A swimmer just out of the river feels cold particularly if it is windy, because of the evaporation of water from his body surface. The evaporation is more on a windy day.
· A thick glass tumbler often cracks when very hot liquid is poured into it because the inner surface of the thick glass tumbler coming in contact with the hot liquid expands more in comparison with the outer surface which has relatively lower temperature. This unequal expansion of inner and outer surface causes the tumbler to crack.
· A train stops when the chain is pulled because of the following mechanism. When the chain is pulled, one small valve gets opened and air enters to the underside of the piston head of the brake cylinder through pipe connection. Initially there is vacuum on both top and bottom side of the piston head. When air enters the underside of the piston head, the piston raises up due to difference of pressure and pulls the brake thus stopping the train.
· A wick in a stove keeps burning continuously as kerosene rises in the wick due to capillary action.
· Alcohol is sometimes rubbed on the body of a person suffering from fever. As soon as it is applied on the body, it evaporates taking away some heat from the body. Since evaporation has a cooling effect, the body temperature can be reduced by rubbing alcohol.
· An electric bulb makes a bang when it is broken because there is a vacuum inside the electric bulb; when the bulb is broken air rushes in at great speed from all sides to fill the vacuum. The rushing of air produces a noise generally referred to as the “bang”.
· An ordinary clock loses time in summer because the length of its pendulum increases, and therefore, its time period also increases. The pendulum takes more time to complete each oscillation and thus loses time.
· Fish and other aquatic creatures can live inside a deep frozen pond because there will always be water just beneath the ice level .
· Food is cooked quickly in a pressure cooker because the boiling point of water increases at high pressure. Food cooks faster at high temperature.
· Formation of shadows can be explained by rectilinear propagation of light
· If a highly corked glass bottle full of water is left out of doors on a frosty night and convert into ice. There is no room available for the increased volume and this may result in bursting of the bottle.
· In a freezer ice cubes will be formed more quickly in trays made of Aluminium because it is a good conductor of heat.
· In mountainous regions, the atmospheric pressure is less than it is at see level water, therefore, boils at a lower temperature(less than 100° C) and food takes more time to cook.
· It is dangerous to sleep in an unventilated room with fire burning inside because the fire produces carbon monoxide and carbon dioxide gases. Carbon monoxide is poisonous and can cause death.
· It is more difficult to walk on ice than on a concrete road because there is very little friction between the ice and feet pressing it.
· Moisture gather on the outer surface of a glass tumbler containing cold water because the water vapour present in the air get cooled and appear as droplets of water on coming in contact with the cold surface of the glass tumbler.
· Pieces of camphor (कपूर) placed on water move about rapidly. This is because of surface tension.
· Soft iron is used as an electromagnet because it remains a magnet only while the current passes through the coil around it and loses its magnetism when the current is switched off.
· Standing in double-decker buses, particularly on the upper floor, is not allowed because on tilting, the centre of gravity of the bus gets changed and it is likely to overturn.
· The basic reason for the extraordinary sparkle of suitably cut diamond is that it has a very high refractive index.
· The boiling point of seawater will be more than the boiling point of pure water because the former contains salt and other impurities.
· The Earth rotates on its axis from west to east. This rotation makes the sun and the stars appear to be moving across the sky from east to west.
· The filament of an electric bulb is made of tungsten because it has a high melting point and can be heated to a high temperature to emit light.
· The freezing compartment inside a refrigerator is at the top because the air in contact with it becomes cold and heavy and sinks downwards, cooling the rest of the compartment.