Do you remember our chemistry experiment with colour changing Oobleck? That was such a fun experiment and the colour changes amazed the kids! Did you know there is another way to make colour changing Oobleck? This time we did it using thermochromatic pigment. It turned into a fascinating look into heat transfer and it’s affect on the pigments while playing with non-Newtonian fluid. This is a mesmerizing Oobleck experiment you must try!
Oobleck RECIPE With Thermochromatic Pigment
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Have you made the leap yet? Have you tried making Oobleck? Non-Newtonian Fluids are so much fun! You can also do some really amazing things with Oobleck. Far beyond the simple mixing of cornstarch and water.
One of our favourite activities was when we did our Oobleck Chemistry experiment that resulted in a gorgeous, colour changing Oobleck. The blues, pinks and purples were stunning, but it was also a fascinating science experiment exploring pH, acids and bases.
We’ve been really into exploring Oobleck lately and wanted to try something new. The result was a Colour Changing Oobleck controlled by temperature.
We’ve had a lot of fun doing Heat Transfer experiments in the past. And this seemed like an interesting experiment. We were not sure how it would work. The results actually surprised us!
Thermochromatic pigments change colour based on temperature. There are a lot of very practical uses for this. One is knowing if bath water is safe for babies. There is also some very fun uses, I mean who hasn’t enjoyed playing with mood rings?
In our case we wanted to use Thermochromatic Pigment in the name of science and education!
The first lesson learned in our journey with these pigments is to be really careful when selecting your pigments. Some of them have VERY high change values. This is the point where the colour changes. The first batch of Thermochromatic Pigment I bought changed temperature at such a high temperature we couldn’t get it to alter unless we used extremely hot temperatures. Much hotter than I wanted with my kids. The temperature listed on the package was 28 C, but we found it needed much higher to get a complete colour change. It may be also due to the fact that this pigment went from coloured to clear. So it took a lot of heat to turn it completely clear.
For my second batch I grabbed three pigments that had change values of either 22 C (72 F) or 2 5C (77 F) and they worked brilliantly! These new pigments also changed from one colour to another. We have Black – Yellow, Red – Yellow and Blue – Violet.
THERMOCHROMATIC PIGMENT OOBLECK RECIPE
For this recipe we used Cornstarch and Water. We have used a number of recipes and definitely have our favourites, but I can buy Cornstarch in bulk really cheap. So when I am doing these experiments, where we might need to make the Oobleck a few times to get it right, I like to stick to the most budget friendly option.
We made one bowl of with each pigment. Into each bowl add:
1 cup cornstarch
1/2 cup water
1 teaspoon Thermochromatic pigment
Mix everything together and explore!
Check out a video of our thermochromatic Oobleck in action!
Playing with COLOUR CHANGING OOBLECK
Although we made all three batches at once, we discovered very quickly that we had to stop and wash our hands in between each bowl to prevent contamination and ensure we could really see and explore the colour changes that happened.
Since the colour changes happened at such a low temperature, I found it best to set the bowls in the fridge. This really brought out the cold colour strongly so once we started playing we could really see the colour change just from the warmth of our hands.
And boy did we see some amazing colour changes! It was fascinating to watch as it would change colour in our hands to the warm colour and then when it fell back the bowl it would change back to cold.
At one point as we were playing we noticed that as the Oobleck would do it’s crazy gloopy, slow drip thing that Oobleck loves to do, that the bottoms of the drips would actually change colour as they cooled from our hands.
The cool thing with these colour combinations was that we had in between colours. So our Black to Yellow would appear green during the transition. Red to Yellow would appear orange (and even pink at times). The Blue to Violet didn’t really have a transition colour. It was really neat seeing the colours transition and change.
We spent so long playing with this Oobleck. It was fascinating. The combination of transitioning between solid and liquid from the Oobleck, with the colour changes from the Thermochromatic Pigment made this a mesmerizing investigation for the kids.
The Science Behind Thermochromatic Pigment
When a substance changes colour due to temperature changes we say it is Thermochromic. This comes from the Greek words thermos (heat) and chroma (color).
Thermochromic pigments use liquid crystals or leucodye technology.
Leucodyes are organic (carbon-based) chemicals that change color when heat energy makes their molecules shift back and forth between two subtly differently molecular structures. These different structures cause the pigment to absorb and reflect light at different wavelengths. This results in the pigment being one of two different colours depending on the temperature.
Pretty neat? Not only do we have heat transfer but we are exploring wavelengths and colours. Plus of course our always fun exploration of non-Newtonian Fluids.
The Science Behind Non-Newtonian Fluids
If you are new to non-Newtonian Fluids you may be wondering what this strange matter is that is turning solid under pressure, then becoming a flowing liquid without pressure.
Non-Newtonian Fluids got this name because they break Newton’s Laws of Fluid Dynamics. Picture how water or syrup flows and moves. It is pretty predictable and you know exactly what will happen.
Oobleck, or non-Newtonian Fluid, doesn’t behave like other liquids. It becomes solid under pressure when you squeeze or push or hit it. Obtaining a play dough like consistency. But release a solid handful of Oobleck and it will flow like liquid through your fingers.
This phenomena is caused by shear thickening. Cornstarch doesn’t dissolve in water, instead the molecules become suspended. If the molecules dissolved we would get a paste or regular liquid (if we used enough water), but instead, we get a suspension which results in this behaviour which kids love to explore.
You can read more about this in our Science Fair Experiment where we really dug into the science of Oobleck.
Have fun exploring Oobleck and Thermochromatic Pigments!
MORE HANDS ON LEARNING FOR KIDS
Colour Changing Oobleck with Thermochromatic Pigment
Learn how to make this hypnotizing non-Newtonian Fluid that also changes colour as you handle it. From solid to liquid, one colour to another, this thermochromatic pigment Ooobleck will wow your kids!
- 1 cup cornstarch
- 1/2 cup water
- 1 tsp thermochromatic pigment
Add the cornstarch to the bowl.
Measure out water and add thermochromatic pigment. Mix.
Add coloured water to cornstarch bowl and mix everything together until completely combined and goes solid under pressure, liquefies without pressure.
Play and explore!