Chemistery

Burn a piece of toast, watch iron rust, mix vinegar and baking soda until it fizzes — something new appears each time. That "something new" is the signature of a chemical reaction, and once you know what's really happening at the atom level, chemistry stops feeling like magic. The short answer: a chemical reaction is a process in which one or more substances (the reactants ) are turned into one or more new substances (the products ) by breaking and re-forming chemical bonds. The atoms themselves aren't created or destroyed — they're just rearranged into new combinations, which is why the total mass stays the same. What actually happens in a reaction Every substance is made of atoms held together by bonds . In a chemical reaction, three things happen in order: Old bonds break in the reactants. Atoms rearrange into new partnerships. New bonds form , giving you the products. Think of it like LEGO. You start with two built models (reactants), pull some b...

Why does a hand warmer get hot while an instant cold pack turns icy — using the same basic idea? It comes down to one of chemistry's most useful distinctions: whether a reaction releases energy or absorbs it. The short answer: exothermic reactions release energy (usually heat) to their surroundings, so things get warmer . Endothermic reactions absorb energy from their surroundings, so things get colder . An easy memory hook: exo = energy exits ; endo = energy goes in . Quick comparison at a glance Feature Exothermic Endothermic Energy flow Released to surroundings Absorbed from surroundings Surroundings feel… Hot Cold Products vs reactants Products have less energy Products have more energy Sign of ΔH (enthalpy) Negative (−) Positive (+) Examples Burning, respiration, hand warmers Photosynthesis, cold packs, thermal decomposition What is an exothermic reaction? An exothermic reaction gives out energy, most often as heat (sometimes light or sound). The prod...