Answer:
A sample of water boils and releases gas.
Explanation:
Physical change is a change where no any chemical reaction takes place only the chemical composition of matter changes. It is a reversible process . 
Burning of newspaper, rusting of iron, plant changes carbon dioxide and water into sugar (photosynthesis) are  chemical reaction and irreversible process.
 
        
                    
             
        
        
        
Answer:
its either A or B most likley A if im wrong then im sorry.
Explanation:
have a wonderfull day
 
        
             
        
        
        
Answer:
I think its False
Explanation:
 ozone layer surroundes the atmosphere and traps the heat
 
        
             
        
        
        
Answer:
The correct answer is <em>b. Negative</em>
Explanation:
An electrolytic cell is based on a reduction- oxidation reaction which is non spontaneous. That means that the standard cell potencial (Eº) is negative. For this reason, an electrical potential must be applied in order to force the reaction. Conversely, a galvanic cell is based on a spontaneous redox reaction, so the galvanic cell produces electrical energy. 
 
        
             
        
        
        
Answer:
 NaF and KBr
Explanation:
These two substances contain pure ionic bonds. LiI is a covalent compound because of the Large polarizing power of Li and the high polarizability of I(Fajan's rules). The other compounds mentioned are organic compounds. They are not soluble in water at all.