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Physical Reactions

It is important to understand the difference between chemical and physical changes. The two types are based on studying chemical reactions and states of matter. We admit that some changes are obvious, but there are some basic ideas you should know. Physical changes are about energy and states of matter. Chemical changes happen on a molecular level when you have two or more molecules that interact and create a new molecule or two. 

When you step on a can and crush it, you have forced a physical change. The shape of the object has changed. It wasn't a change in the state of matter, because the energy in the can did not change. When you melt an ice cube (H2O), you have also forced a physical phase change by adding energy. That example caused a change in the state of matter. You can cause physical changes with forces like motion, temperature, and pressure. 

"Chemical Vs. Physical Change" Chem4Kids.com. Andrew Rader Studios. 19 September 2013 <http://www.chem4kids.com/files/matter_chemphys.html>
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