Answer: The closeness, arrangement and motion of the particles in a substance change when it changes state. Materials are a store of internal energy , due to the motion of particles and the chemical bonds between them. When a substance is heated, its internal energy increases: the movement of its particles increases.
Explanation:
 
        
             
        
        
        
Explanation:
here's the answer to your question
double arrow just mean that it's a reversible process, and the reaction can go back and forth. 
 
        
             
        
        
        
Dalton postulated that atoms of the same elements had the same mass while atoms of different elements had different masses. 
The discovery of isotopes revealed that atoms of the same element did not necessarily have same masses, they could have different masses.
Therefore, the modern periodic table that we use nowadays contains the average atomic mass of all the isotopes found for a given element.
        
             
        
        
        
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Answer: Na2CO3 + 2 HCl → 2 NaCl + H2CO3
I hope this helped!
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- Zack Slocum
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