Water is a substance essential to human life. According to Healthline, water makes up up to 75% of a child's body! If you're dehydrated without water, it is possible that you might even die! Water is composed of 2 hydrogen atoms and 1 oxygen atom. If water is heated to high temperatures, it will start to evaporate, or turn into water vapor. If a metal bottle with cold water is placed in a hot setting, water will start to condense, or collect, on the bottle's sides. Without water, it would be impossible for humans to survive, and so, it is essential to us.