Explanation:
A single-replacement reaction replaces one element for another in a compound.
A double-replacement reaction exchanges the cations (or the anions) of two ionic compounds.
A precipitation reaction is a double-replacement reaction in which one product is a solid precipitate.
Solubility rules are used to predict whether some double-replacement reactions will occur.
 
        
             
        
        
        
We are given with the following pairs:
<span>carbon and oxygen
hydrogen and helium
gold and silver
and we are asked if there is a pair that will produce the same spectrum. The answer is
</span>No two elements produce the same spectrum.This is because a light spectrum is unique to each element.
        
                    
             
        
        
        
C is the correct answer (CaF2) (sorry dont have subscript)
Explanation: synthesis reaction forms a compound and calcium reacting with fluorine produces Calcium Fluoride (CaF2) chemical name
        
                    
             
        
        
        
Sucrose <span>is not an example of a polymer. The answer is letter C. Polystyrene, Nylon and PVC or poly vinyl chloride are examples of polymer</span>
        
                    
             
        
        
        
Answer:
The molecules in the water become more separated due to heat.