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.
Kittens can be weaned when they begin eating solid foods at approximately 4-6 weeks old; offer them wet food mixed with water at 4 weeks. When the kittens are fully weaned from mom, the mom should be spayed, and then either adopted out or returned outside. The kittens should be fixed and adopted out around 8-10 weeks of age. Handle the kittens frequently after 5 weeks old to help with socialization.