Answer: Chemical composition modification (or, physical signal would be color).
        
                    
             
        
        
        
Answer:
The elements in the reactants are the same as the elements in the products.
Explanation:
You can't have more or less elements or atoms, but you also can't just have the same number of atoms because then it could be different elements, which can't happen.
 
        
                    
             
        
        
        
Answer:
a) 
, 
, b) 
, 
Explanation:
a) The ideal gas is experimenting an isocoric process and the following relationship is used:

Final temperature is cleared from this expression:


The number of moles of the ideal gas is:



The final temperature is:


The final pressure is: 



b) The ideal gas is experimenting an isobaric process and the following relationship is used:

Final temperature is cleared from this expression:




The final volume is:



 
        
             
        
        
        
Lithium dihydrogen phosphate