Isn't a chemical change like something that's not a physical change or physically changed but is something that uses natural chemicals? that's my guess sorry if it's wrong I think I'm wrong though
        
                    
             
        
        
        
<span>the simplest organic molecules, consisting of only carbon and hydrogen and with only single bonds between carbon atoms. 
Ex. Methane, Ethan, Propane, Butane
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Answer:
New experimental methods 
Technological inventions
Explanation:
A scientific theory is usually not based on speculation. Scientific theories must have a solid empirical basis. 
However, experimental methods are limited to the caliber of equipments available at the time in which a theory is formulated. With advancing years, more technological sophistication leads to the invention of new instruments and ultimately, the development of new experimental methods.
These innovations are likely to alter existing scientific theories as new evidences emerge, hence the answer.
 
        
                    
             
        
        
        
Answer:
<h2>81.5 g</h2>
Explanation:
The mass of a substance when given the density and volume can be found by using the formula
mass = Density × volume
From the question we have
mass = 25 × 3.26 
We have the final answer as
<h3>81.5 g</h3>
Hope this helps you