Why do the inner walls of a vacuum flask have a silver coating?
a) to stop heat loss by radiation
b) to reduce heat loss by radiation
c) to reduce heat loss by conduction
d) to reduce heat loss by convection

Answer:

The inner walls of a vacuum flask have a silver coating to reduce heat loss by radiation.

Explanation:

The vacuum flask has an inner silver lining to prevent the transfer of  heat by radiation. Radiation is a process where the emission or transformation of energy happens in the form of wave or the  particles through the material medium.

Vacuum flask being working as thermal insulator helps in maintaining the substance its actual temperature for a long time. The silver lining acts as a reflector .It  prevents the heat radiation to released out of the flask.  

your parents i think this could be it

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.