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Physical changes are those where new substances are not formed and the changes are, generally, visible (or can be easily observed). Boiling and melting are example of physical changes. In each of these examples, even though molecular rearrangement may take place, the identity of the substance does not change.
Chemical changes are characterized by formation of new chemical species. Reaction of hydrogen and oxygen to generate water is a chemical change. So is rusting of iron.
Photosynthesis is the process through which plants convert light energy into chemical energy. Here is the chemical reaction involved:
`12 H_2O + 6 CO_2 + Light -> C_6H_(12)O_6 + 6O_2 + 6H_2O`
As we can see, water and carbon dioxide combine to form glucose and oxygen. Since new chemical species are formed, photosynthesis is clearly a chemical change.
Hope this helps.
Photosynthesis is a chemical change.
The main thing to know in order to figure out this question is to understand the difference between a physical and chemical changes. A physical change is one were the physical properties are altered. The identity of the substance remains unchanged. For example, changes in phases, shapes, or even sizes. A chemical change is a change were one or more substances or reactants are changed into one or more new substances or products (a chemical reaction).
Photosynthesis falls in the latter definition because of its nature. Here the the given reaction:
`6CO_2 + 6H_2O ---> C_6H_(12)O_6 + 6O_2`
As you can see, there is a chemical reaction that occurs, which allows it to be classified as a chemical change.
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