Photosynthesis is the process through which plants convert light energy into chemical energy. Here is the chemical reaction involved: 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.
I hope this helps answer your question. :)
Answer is gas for sure and I think it’s ice for question 2
Rubidium would exhibit the greatest shielding [ effect. ]
Answer:
a) 
b) 
c) 
Explanation:
Hello,
In this case, in each reaction we must subtract the Gibbs free energy of formation the reactants to the Gibbs free energy of formation of the products considering each species stoichiometric coefficients. In such a way, the Gibbs free energy of formations are:

So we proceed as follows:
a)

b)

c)

Regards.