You will need:
1- Wide glass/jar/bottle
2- Food coloring
3- Vegetable oil/Baby oil
4- Water
5- Alka-Seltzer tablet
Steps:
1- Fill the glass/jar 3/4 of the volume with oil. (Baby oil works the best because It is clear and allow the food coloring to really stands out). Let your children assist you because it is going to help their fine motor skills and teach them about measurements.
2- Fill the rest of the glass/jar with water, leaving 2-3 inches empty at the top.
a-Have your children observe the separation between the oil and water and how water falls through the oil and lands at the bottom of the glass.
b-Explain to them that water molecules are not attracted to oil molecules. Water is more dense than oil.
3- Add food coloring (about 10-12 drops) after the water has settled for a couple of minutes. The food coloring has the same density as the water so it sinks through the oil and mixes with the water.
4- Cut the Alka-Seltzer tablet into small pieces. Drop one piece of the Alka-Seltzer tablet into the glass/jar. As soon as the bubbling stops, add another tablet piece. It might erupt out of the container. Be prepared for a little mess.
Explanations:
1- The reaction of Alka-Seltzer with water produces a gas called “carbon dioxide.”
2- Gas bubbles have the ability to stick to the water droplets.
3- The combination of water and gas has less density than oil, so they rise to the top.
4- The gas bubbles start to break and release into the air and the water gets heavy and sinks back down to the bottom of the container. It does this over and over again until the tablet has completely dissolved.
Questions to ask your children:
1- Does the oil pour differently than the water?
2- What do you notice about the food coloring drops when added to the oil/water?
3- What do you think will happen if another piece of tablet is added?
4- How is the colored water moving up through the oil?
5- What if you drop a whole tablet in? What is going to happen?
6-What happens if you sprinkle some salt into the lava lamp after the bubbling stops?