Chemical reactions: the basics

In short: In a chemical reaction substances combine to form new substances with different properties. Atoms are rearranged but not created or destroyed.

In more detail: The law of conservation of mass: the total mass stays the same.

In detail

• Reactants and products: Starting materials react to end products, e.g. hydrogen + oxygen → water.
• Reaction equation: 2 H₂ + O₂ → 2 H₂O.
• Energy: Exothermic reactions give off heat (combustion), endothermic ones absorb it (verbrennung-und-feuer).
• Catalyst: Accelerates reactions without being consumed.
• Speed: Temperature, concentration and degree of subdivision influence it.
• Acids and bases: Neutralisation yields salt and water (ph-wert-saeuren-und-laugen).
• Redox reactions: Electrons move, e.g. in rusting.
• Everyday life: Cooking, baking, digestion, batteries (atom-und-molekuel).