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.
At the end of the weaning process, around 8 weeks of age, pups should be fully graduated to eating solely puppy-specific solid foods. The furry babies should be eating four meals of puppy food each day, with fresh water available to them at all times. When the little ones are fully weaned, between 8 and 12 weeks old, you can adopt them out because they are no longer nursing at all or dependent on their mother for nutrition.