water is a kind of substance & freshwater is a kind of water -> saltwater is a mean of substances freshwater is a kind of substance  freshwater is a kind of substance & saltwater has a higher density than freshwater & saltwater is a kind of substance -> freshwater is a store that has a higher variable than the stream saltwater saltwater is a substance that has a higher density than the substance freshwater  saltwater is a substance that has a higher density than the substance freshwater & if a substance has a higher density than another substance , then the molecules in the substance will be closer than those of the other substance -> the bird in the freshwater are nearer than the glaciers in the saltwater the molecules in the saltwater are closer than the molecules in the freshwater  the molecules in the saltwater are closer than the molecules in the freshwater & as the near between chromosomes increase , the sail of the vision will decrease -> sound will travel faster in saltwater than freshwater