How Do Toys Change Color In Water?
If you’ve ever seen your child’s toys changing in the warm water of the bath, you’ve probably wondered how the heck toys can change color without being painted.
The answer is a bit complicated because it involves some serious chemistry. But by the end of this article, you’ll know exactly how toys change color in the water. You might even be able to explain it to your child.
Phase Changes
Think about water. We’re familiar with water in three phases: liquid, solid, and gas. But we’re also familiar with the way that the color of water changes throughout its phases.
In its liquid form, we expect water to be clear or to have a blue hue. We only see the blue hue if there is a lot of water in one spot because each tiny unit of water doesn’t change the optical properties of the light that passes through it very much.
We need to have a lot of water in one place to make the light that passes through it look blue. Anything less, and there isn’t enough of an impact on the light for us to notice.
In ice, we understand that there is a lot less light that can pass through. Blocks of ice are not entirely clear, and a lot of the light does not pass through them. When we melt ice into water, more of the light can pass through.
So, now that we’ve established that a chemical’s phase — whether it is a solid, a liquid, or a gas — changes the way light refracts through it, how does that relate to the way that toys change color? Toys don’t have water inside of them when they change color.
And toys aren’t making ice or gas rapidly.
The principle of a phase change doesn’t necessarily have to occur as a result of a change in temperature. Sometimes, it can occur thanks to a chemical reaction. In the case of children’s toys, the color change is caused by both a change in temperature and also a chemical reaction.
Reactions To Change Color And Phase
When your child exposes their toy to water, the toy changes color gradually under the surface. A phase change is responsible for the change in color, but the chemical reaction that occurs may surprise you.
Certain chemicals like solvents and salts can reversibly undergo chemical reactions when exposed to different temperatures.
For instance, one chemical can convert into the other chemical when the mixture is hot and then convert back into the original chemical when the mixture is cool. This is exactly what is occurring when a toy changes color.
When the toy is exposed to the water, its temperature changes. This change in temperature allows the chemicals stored in the toy to react, resulting in the mixture changing phase. When the mixture changes phase, the new phase refracts light differently than the old phase.
The more light that the new phase absorbs, the darker the color that the toy becomes. Once the temperature returns to normal — room temperature — the reaction reverses itself and the original color returns.
Other color changing toys could work in a slightly different way, but most follow this formula because it is very easy to adjust to generate different colors depending on the toy’s needs. Furthermore, the chemicals used in this method are safe enough for children to enjoy.
Understanding this paradigm explains many of the different modalities for color changing in toys. Some toys change color only when exposed to hot water, whereas others will change color when exposed to cold water.
The water itself isn’t even participating in the chemical reaction; it’s just an effective way to very quickly change the temperature of the toy. The important thing to remember is that room temperature is seldom as cool as tap water or as warm as bath water.
Solving For Solvents
There are many different chemical combinations which change phase reversibly in response to changes in temperature. Chemically, most of these combinations are constituted by a salt and a solvent.
The solvent will have the salt dissolved inside of it under normal conditions. When the temperature changes, the salt will solidify, precipitating out of the solvent and causing the color to change as a result. The solvent itself will also have its chemical properties changed.
If you purchase a commercially available science kit toy, you can even test some of these chemical reactions out yourself for the enjoyment of your child.
Try explaining the way color changes work to your child when they play with their toys. Building an early fascination with science is a great way to raise an educated child, and there’s no such thing as too much curiosity.
