1) Endothermic reactions:
a) The reaction between ammonium nitrate and water absorbs heat from the surrounding environment.
There are two types of reaction: endothermic reaction (chemical reaction that absorbs more energy than it releases) and exothermic reaction (chemical reaction that releases more energy than it absorbs).
b) Ammonium chloride dissolved in a beaker of water makes the beaker cold.
Dissolving this salt absorbs heat from beaker.
c) Water separates on hydrogen and oxygen when an electric current is run through it.
Electrolysis of water is the decomposition reaction (heat is required), because from one molecule (water) two molecules (hydrogen and oxygen) are produced. Water is separated into two molecules.
2) Exothermic reactions:
a) Three drops of concetrated sulfuric acid added to 100 milliliters in a beaker makes the beaker hot.
Energy is released, beaker absorbs that heat.
b) Uranium atoms are split to produce nuclear energy.
Nuclear energy is released.
c) Methane and oxygen are combined to produce methanol and heat.
Balanced chemical reaction: 2CH₄ + O₂ → 2CH₃OH + heat.
