Answer:1) It is due to large cohesive force acting between the molecules of mercury that the droplets of mercury when brought in contact pulled together to form a bigger drop in order to make potential energy minimum. The temperature of this bigger drop increases since the total surface area decreases.
2) A spherical shape has the minimum surface area to volume ratio of all geometric forms. When two drops of a liquid are brought in contact, the cohesive forces between their molecules coalesce the drops into a single larger drop. This is because, the volume of the liquid remaining the same, the surface area of the resulting single drop is less than the combined surface area of the smaller drops. The resulting decrease in surface energy is released into the environment as heat.
Yes, I agree with Bryce and his lab partner because titration is completed when the solution changes its colour. Add chemical from the burette until the solution change its colour so then calculate the amount of chemical is used from the burette and the time at which the titration is completed. Always be careful for calculating the titration in order to get accurate data of the solution.