The three changes of state during which energy is absorbed are:
1. Change from solid to liquid - Melting.
2. Change from liquid to gas - Vaporization
3. Change from solid to gas - Sublimation
All these changes of state require heat energy to break the attractive forces that hold the particles of the molecules together, so that they can move into more disorderly states. For instance, when heat is applied to a solid, the solid absorbs the heat and use it to break the attractive forces that are holding the molecules of the solid together. At a particular temperature, the attractive forces will be completely overcome and the solid framework will collapse, thus leading to the melting of the solid. 
 
        
                    
             
        
        
        
I think the answer is A..... ps c and d are the same
        
                    
             
        
        
        
I think it’s a because that’s the easy question every
        
                    
             
        
        
        
Diffusion occurs because of the movement of molecules from the region of higher concentration to the region of lower concentration. This movement of molecules occurs due to a thermal motion. Diffusion normally occurs between two compartments having difference in concentration. In case of fluid it moves from the region of higher concentration to the region of concentration until a balance is reached. The process of diffusion is very important for the humans as well. The oxygen that humans breathe in gets diffused with the blood.<span> 
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The answer is guard cells. 
Guard cells are cells surrounding each stoma. They help regulate the rate of transpiration by opening and closing the stomata. They are specialized cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. They are produced in pairs with a gap between them that forms a stomatal pore (stoma).