Thixotropy facts for kids

Thixotropy is a special property of some gels and fluids. Imagine something that is thick and gooey when it's still, but becomes thin and runny when you shake it or stir it. That's thixotropy! It means the material changes how easily it flows depending on if it's moving or not.

When a thixotropic fluid is left alone, it's thick and doesn't flow much. But if you apply a force, like shaking or mixing it, it becomes thinner and flows more easily. Once the force is removed, it slowly goes back to being thick again. This change in how thick or thin a fluid is called viscosity.

Some fluids are the opposite, called anti-thixotropic. They get thicker or even solid when you shake or mix them for a while. However, these are much less common than thixotropic fluids.

Everyday Examples of Thixotropy

You might have seen thixotropy in action without even knowing it! It's quite common in nature and in products we use every day.

Walking on Sand

Have you ever walked on wet sand at the beach and felt it become squishy or even liquid under your feet? This is a thixotropic response. The pressure from your foot makes the sand particles move closer, releasing trapped water and making the sand temporarily flow like a liquid. In extreme cases, this can lead to quicksand, which is very dangerous.

Mud and Landslides

Some types of clay are thixotropic. This is very important for engineers who build things. For example, a landslide can happen when a stable-looking mud bank suddenly turns soupy and slides down a hill after heavy rain or an earthquake. The water and shaking make the clay less stable. A lahar, which is a mix of volcanic ash and water, also shows thixotropy. It flows like a river when moving but quickly hardens when it stops.

Honey and Body Fluids

Even some types of honey, like heather honey, can be thixotropic. It might be thick in the jar but becomes runnier if you stir it. Another interesting example is the synovial fluid found in your body's joints, like your knees. This fluid helps your joints move smoothly. It's thick when you're resting, but becomes thinner when you start moving, helping to lubricate your joints.

Products We Use

Many products you use daily are designed to be thixotropic.

• Paint: When you open a can of paint, it's thick so it doesn't drip everywhere. But when you stir it or apply it with a brush, it becomes thinner, making it easy to spread. Once on the wall, it quickly thickens again so it doesn't run down.
• Toothpaste: Toothpaste is thick enough to stay on your toothbrush, but when you brush, the force makes it spread easily in your mouth.
• Ketchup: Some types of ketchup are thixotropic. It's hard to get out of the bottle until you shake it, making it flow more easily.

Images for kids

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  Quicksand on the shore of the River Thames. Quicksand demonstrates thixotropy, becoming liquid when disturbed.

See also

In Spanish: Tixotropía para niños