18. In some chemical reactions, such as
photosynthesis, several different compounds
take part in the reaction. How do you think that
atoms present at the end of this kind of reaction
compare to the atoms present at the beginning
of the reaction? Explain.

The atoms present at the beginning of the reaction is equal to the atoms present at the end of the reaction.

The reason for this is because matter can neither be created nor be destroyed in an ordinary chemical reaction.

Explanation: During photosynthesis, six molecules of water reacts with six molecules of carbon dioxide to form one molecule of glucose and six molecules of oxygen. The equation for the reaction is 6CO2 + 6H2O --> C6H12O6 + 6O2

At the beginning of the reaction, there is 6 carbon atoms, 18 oxygen atoms and 12 hydrogen atoms while at the end of the reaction, there is 6 carbon atoms, 12 hydrogen atoms and 18 oxygen atoms.

The reason for this is because according to the law of conservation of mass, matter can neither be created be created nor be destroyed in an ordinary chemical reaction. There the number of atoms present at the beginning of the reaction must be equal to the number of atoms present at the end of the reaction.

materials water oxygen those are the things i can think of in this moment.