Questions

Jello is a colloid, a semi-rigid structure i.e, semi-solid suspended in a liquid. When you Heat it up a bit and you'll break the protein bonds of the gelatin and it will liquefy completely and if you freeze, it becomes solid.

A restrictive clause is one that limits the meaning of the word it describes.

For example :: 

The girl who lives next door is beautiful.

This restrictive clause limits "the girl" to say it's specifically the one next door.

It is very hard to catch breathe when you run fast.

Part of the heat is conducted away by the metal table. Convection currents in air near the surface of the coffee are set up which accounts for some heat loss. Heat is also lost by radiation from the hot coffee to the surroundings. Most of the heat is lost by the last method.

The United Nations Public Service Day is observed every year on June 23 to recognize the work of public servants and to encourage young people to pursue careers in the public sector. The day is also observed to celebrate value and virtue of public service to the community and to raise awareness regarding the contribution of public service in the development of society and honouring the work of public servants.