STEM Learning: Lava lamp density

Wednesday 2nd May 2018

In an early childhood environment, science can be looked at in terms of exploring, discovering and nurturing the children’s curiosity about the world around them. Teaching science is not only about formal experiments and chemical reactions, for young learners, science can be an extension of their everyday world. Their natural curiosity and love for play can make learning scientific skills fun and meaningful. (Early Childhood Australia)

Today, we continue to create simple chemistry experiments because of the visual reactions. Chemistry is a reaction or a change between two or more substances. Sometimes it’s a slow reaction and sometimes it’s a crazy wow reaction like our volcanoes. The ingredients we used today included:

+ Plastic container (using a bottle with lid is better) 

+ Vegetable oil

+Water 

+ Food colouring 

+ Alka-Seltzer tablets 

We began by pouring oil into our container about two thirds of the way and the rest of the way with water. We then waited for the two layers to settle and bubble and then added the food colouring. We watched as we saw the food colouring spread across the mixture and attaching itself to the water molecules. We then broke the tablet into small pieces and dropped small pieces of the tablet into the bottle to create a bubbly fizzy lava lamp. 

The effect that you see here occurs when there is a difference in density between the oil and the water. The oil floats on top of the water because it is less dense or lighter than water. The food colouring has the same density as the water so it will sink through the oil and mixes with the water. When you add the tablet it sinks to the bottom then starts to dissolve. As it dissolves it makes gas, carbon dioxide. Gas or air, is lighter than water so it floats to the top. The air bubbles bring some coloured water with them to the top. When the air comes out of the coloured water blob, the water gets heavy again and sinks. It does this over and over again until the tablet is completely dissolved. The reason Alka-Seltzer fizzes in such a way is because it contains citric acid and baking soda (sodium bicarbonate), the two react with water to form sodium citrate and carbon dioxide gas (those are the bubbles that carry the coloured water to the top of the bottle). 

The children formed their own opinions on what was occurring and could see how water and oil do not mix very well. June commented “Fizzy, fizzy drink.” Penelope observed the chemical reactions and said “The colour is moving” as she watched the food colouring move its way around the container as it began to sink and then fizz. We added more Alka-Seltzer to keep the experience moving and to observe the changes. When it ran out, we placed a lid on the container and gave it a good shake to see how bubbles form and then separate again.

As educators we were role modelling appropriate language during children’s experience to help introduce science concepts, while also extending their language skills. We used words such as ‘separate’, ‘repel’ and ‘chemical’ to explain to our children to help them to develop their understanding of scientific concepts.

To extend this experience we may ask:

+ What happens if you put the cap on a bottle this time after dropping the fizzy tablet in?

+ What if you drop a whole tablet in?

+  When it stops bubbling, try sprinkling some salt into your lava lamp. What happens?

+ When we tip the bottle back and forth, what happens then?

Lava Lamps are fantastic for children needing to settle or calm down. We are going to make a few lamps out of recycled plastic bottles to place in our room.