Drinking water, which we believe to be pure is actually a little hypertonic as it contains a lot of salts and sugars. The water we normally drink from common sources says taps, bottles etc contain enough impurities which affect tonicity of the water. Tonicity is the ability of a solution to draw or repel water from adjacent solutions when it is separated by a membrane. Hence, it is said that a 100% pure water can kill you.
