in Telangana and AP. The questions are from Physical Sciences subject
for English medium students.
Q: Why does we get dew on the surface of cold soft drink bottle kept
in open air?
A: It is because of condensation of water molecules in the air on the
surface of cold drink bottle. When the water molecules in air, during
their motion strike the surface of cold soft drink bottle, they loose
their kinetic energy. When the water molecules loose their energy
their temperature falls down and so they condense as water droplets on
the surface of the bottle.
Q: What is baking powder? How does it make the cake soft and spongy?
A: Baking powder is a mixture of baking soda and tartaric acid.
When baking powder is heated it releases CO2 gas due to which the cake
rises and becomes soft and spongy.
Q: Why is the angle of reflection equal to the angle of incidence when
a light ray gets reflected from a surface?
A: Light selects a path which takes least time to travel.
This principle was first given by Fermat an amateur mathematician. It
is also applicable to reflection of light. When light gets reflected
from a surface, it selects the path that takes the least time. This is
why the angle of incidence is equal to the angle of reflection.
Q: What do you mean by corrosion? How do you prevent it?
A: Corrosion: When some metals are exposed to moisture, acids etc,
they tarnish due to the formation of respective metal oxide on their
surface. This process is called corrosion.
Corrosion can be prevented or at least minimised by shielding the
metal surface from oxygen and moisture. It can be prevented by
painting, oiling, greasing, galvanizing, chrome plating or making
alloys.
Q: Equal amounts of water are kept in a cup and a dish. Which will
evaporate faster? Why?
A: Water in the dish evaporates faster than that in the cup. The rate
of evaporation of a liquid depends upon its surface area exposed. As
more surface of water in a dish is exposed than in a cup, water
evaporates faster in the dish.
Q: Why does transfer of heat energy take place between objects? (1 Mark)
A: When two objects are placed in thermal contact, heat energy will be
transferred from the hotter body to the 'colder body'.
Transfer of heat energy take place between two objects due to
temperature difference in the objects.
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