Chemical Reactions

A chemical reaction is a process in which substances called reactants are transformed into new substances known as products. During the reaction, atoms are not created or destroyed. Instead, the bonds between atoms break and new bonds form, rearranging the atoms into different combinations. This is why the total number of each type of atom remains the same before and after the reaction, following the law of conservation of mass.

Chemical reactions happen constantly around us. Iron rusts when it reacts with oxygen and moisture, food changes as it cooks, plants produce sugars through photosynthesis, and our bodies carry out thousands of chemical reactions every second to release energy, repair tissues and support life. Some reactions occur quickly, while others take hours, days or even years.

Many chemical reactions involve noticeable changes, such as a color change, the release of heat or light, the formation of bubbles from a gas, or the appearance of a solid called a precipitate. However, these signs are not present in every reaction. Temperature, concentration, pressure and the surface area of solid substances can affect how fast a reaction takes place.

Some reactions also require a catalyst, a substance that speeds up the reaction without being consumed. Chemists study these processes to better understand matter and to develop medicines, new materials, cleaner energy technologies and more efficient industrial processes. Learning how chemical reactions work also helps explain many everyday phenomena, from baking bread to charging a rechargeable battery.