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.

Vehicle skids are most likely to be caused by Driving too fast on slipping road.

A closed room is aplace where charcoal is burnt in limited supply of air. There is every chance for the formation of the deadly poisonous carbon monoxide, which when inhaled, reacts with the iron in haemoglobin of blood and prevents the supply of oxygen. It is said to be treacherous as there can be no previous warning of its presence because it is an odourless and colourless gas.

The process which wherein an Ecosystem may renew itself is known as Ecological Succession.

The time scale may be decades or a million of years after a mass extinction. 

It may be achieve over a period of time.