How a liquid motion lamp works
...lamp must be discussed. The liquid inside of the lamp is actually made of two separate compounds, insoluble with one another. This means that the two liquids will not mix or dissolve much like oil and vinegar salad dressing. If one were to closely examine a container of oil and vinegar that has been sitting for a while one will notice that the oil rests on top of the vinegar. The liquids are immiscible. This principle is what gives contrast within the lava lamp. Since the liquids will not dissolve they remain separated allowing you to distinguish between the two. The exact ingredients of the liquids in the lamp remain a trade secret and it is this special combination of chemicals that frequently elude amateurs attempting to construct a lava lamp of their own. What we do know is that the liquids must be very close in density in order for the lava lamp to work properly (Gelbert). Density is the amount of mass present in a unit of volume. When no heat from the lamp is present, there is no transfer of heat allowing the two liquids to exist in thermal equilibrium. This follows the zeroth law of thermodynamics. The liquid with the higher density will rest at the bottom of the lamp while the less dense liquid will float on top due to a principle known as Archimedes’ principle. Archimedes’ explains how buoyant forces act on an object in fluid causing it to float. A buoyant force works upward on the object and is equal to the weight of the fluid the object is displacing and so the object floats (Bloomfield, 124). When an object sinks, like in the case of the cooled lava lamp the object is heavier than the fluid it is displacing. The cooled “lava” sinks and rests at the bottom because it has more mass per unit of volume (density) than the surrounding liquid and is therefore heavier than the fluid it is displacing. Once the lamp is turned on, heat is transferred from the bulb to the glass container through radiation. The glass is then heated through conduction as the molecules in the glass will start moving more rapidly and bumping into surrounding molecules and eventually transferring heat throughout all of the glass increasing its molecules’ kinetic energy. The heat is transferred to the fluid in the same fashion since it is in direct contact with the glass. As kinetic energy increases the molecules move further and further apart from each other causing the substance to expand so the once denser fluid becomes less dense since there is a decrease in mass per unit of volume. The mass is more spread out. This is precisely why the two fluids must be similar in density but not the same. The less dense fluid now rises to the top while the fluid which was originally less dense sinks. Since the transfer of heat is not instantaneous but gradual, only portions of the fluid rise instead of the entire mass rising upward at once. The same principles apply when the fluid cools off towards the upper region of the glass casing. There is a drop in temperature once the fluid reaches the top of the cylinder and heat is transferred again through conduction but this time from the fluid to the glass and then eventually into the air, causing the molecules in the fluid to slow down. The change in temperature causes the fluid to contract and sink to the bottom only to be reheated continuing this heat...