The description of hell is very simple. It is literally being in a fireplace. In the hell the doomed souls drink boiling water. The Koran makes quite clear what this means.

So, there were some among them who believed in it, and there were others among them who turned away from it. Enough (for the latter) is Jahannam, a fire ablaze!

Those who have disbelieved in Our verses, We shall certainly make them enter a fire. Whenever their skins are burnt out, We shall give them other skins in their place, so that they may taste the punishment. Surely, Allah is All-Mighty, All- Wise.

Everybody has had the experience of what it is like to come into contact with fire. When you touch something that's too hot the hand withdraws in a reflex, The pain is sharp and lasts for a long time. Also, everybody has had the experience of accidentally having one's lips come into contact with a liquid that's too hot to drink.

The description of heaven is just as simple. It's a place where there are trees and shadow and water flows through it.

As for those who have believed and have done good deeds, We shall admit them to gardens beneath which rivers flow, where they will live forever. For them there are wives purified. We shall admit them to an umbrageous shade.

Translation of Quran by Shaykh Mufti Taqi Usmani

These very concrete descriptions refer to experiences the people are known to have, certainly in the time and place the Koran originated. The contrast between open fire and the oases in the desert is known by everyone from experience. These descriptions will elicit a very strong fear-response, especially in children.