Does adding salt to water change how fast it moves when heated? Convection (the rising and falling of liquid as it warms) happens all around you. It drives ocean currents and even makes lava lamps work. Fill two heat-proof containers with water and place them on hot plates. Add salt to one container until no more dissolves. Then add food coloring and liquid soap to both. Turn on the heat and watch the soap move. You will see a clear difference in speed between the plain water and the salt water.