Chemical reactions and catalysts. A chemical reaction involves a chemical change, which happens when two or more particles (which can be molecules, atoms or ions) interact. For example, when iron and oxygen react, they change to a new substance, iron oxide (rust).
It's important for parents to start weaning babies from bottles around the end of the first year and start getting them comfortable drinking from cups. The longer parents wait to start the transition, the more attached kids become to their bottles and the more difficult it can be to break the bottle habit.
If I'm breastfeeding my child, do I wean to the bottle or to the cup? Most breastfed babies are given breast milk from the breast and from a bottle during the first year of life. If you have breastfed your baby only from the breast for nine or more months, wean your child to a cup rather than to a bottle.