Covalent compounds are the compounds which are combined by very weak forces generally they cant spilt into to ions so and also they are not so stable than ionic compounds 
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There are many uses
actually h20(water) is a covalent compound and it is used in cooking,drinking,washning,bathing................etc
Also the fossil fuels are formed due to covalent bonds
also according to graham's law of diffusion purfumes are also covalent and they diffuse out easily through a small pore
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