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.
The best time to wean is between 7 and 8 weeks of age but you also need to introduce cat food before they are weaned here is a great website on how to wean a kitten the right way it should be really helpful http://petcaretips.net/weaning_kitten.html I hope all your kitties do really well.