Ok so i have 3 beakers of clear liquid each holding a different substance, water, magnesium sulphate and sodium carbonate how can i identify them by adding other solutions?

For water you could add oil..ex: cooking oil separates form water because water is heavier than oil.

For Magnesium Sulfate you could add Sodium Carbonate..ex: Sodium Carb reacts to Mg Sulfate adding a darker hue to the liquid and adding a lot of bubbles.

For Sodium Carbonate you could add Sulfuric Acid..ex: Sulfuric Acid would add a reaction to the Sodium Carb that would resembling water boiling 

H0P3 It H3LPS :)