Lava Lamp Demonstration

What you will need:

• a clean bottle of any kind
• baby oil or vegetable oil
• 3/4 cup of water
• food coloring
• fizzing tablets (Alka-Seltzer)

Instructions:

1.  Pour the water into the bottle.

2.  Pour the vegetable oil into the bottle until it is almost full.

3.  Observe the water and oil separate forming layers.

4.  Add 15 drops of food coloring to the bottle.

5.  Observe the food color mix with the water.

6.  Break the fizzy tablet into pieces and add a little at a time, or add the entire tablet at once. The tablet will sink to the bottom and the show will begin!!

7.  When the reaction stops working, just add another fizzy tablet!!!

How it works:

The first thing that you should have observed in the beginning of this demonstration is that water and oil do not mix!! This is because the water molecules are not attracted to the oil molecules.  You could even say they are mortal enemies.  To demonstrate this, shake up the bottle once you have the oil and water in the bottle.  The oil breaks up into tiny bubbles, but never mixes with the water.  When you add the food coloring, you will notice that it mixes with the water, but never mixes with the oil.  We could infer that the food coloring is the water's ally in the battle of molecules scenario. 

The second observation to detect is the liquids in this experiment form layers.  This is a great illustration of density.  Density is the characteristic property of a substance that shows the relationship between the mass of a substance and how much space it takes up (volume).  We can quantify density using the equation D = M/V.  The oil floats on top of the water because it is less dense.  The food coloring has the same density as the water, so it sinks through the oil and mixes with the water.

And finally, when you drop the fizzy tablet into the bottle it sinks to the bottom and starts to dissolve.  As the fizzy tablet dissolves, it reacts with the water to form the gas carbon dioxide (CO2).  The carbon dioxide gas is less dense than the water, so it floats to the top.  When the gas bubbles pop, the water sinks to the bottom again. It does this over and over until the fizzy tablet is completely dissolved!

Demonstration Extensions:

• Does the temperature of the water affect the reaction?
• What happens when you put the cap on during the reaction?
• Does the size of the fizzy tab affect the amount of bubbles produced?