Challenger Center: Garriott Science Challenge

How and Why Do Liquids Mix Together? (Learning about coalescence, immiscible liquids and diffusion)

Some liquids will easily mix, others will not. The ability to mix depends on the properties of the liquids and gravity. Liquids that do not mix are called immiscible liquids. When two liquids that are immiscible are stirred together, they will quickly separate. Coalescence is the process by which two or more droplets or particles merge during contact to form a single droplet. Coalescence is important in the formation of rain, planets, stars, and welding two pieces of metal together.

Richard Garriott experimented on orbit to get a better understanding of how liquids mix in space. To study immiscible liquids, he will shake containers of oil and water. He videotaped the behavior of the mixed liquids over time.

To study coalescence, he collided water drops of a variety of sizes and with a variety of speed to observe patterns of coalescence (joining). He videotaped the collisions for accurate, detailed views of the joining process. To study diffusion, he placed a layer of dark colored water on top of clear water in a small container.

Essential Questions

How does the size and speed of impact of two water drops affect their coalescence (joining)?
How does gravity affect the speed at which immiscible liquids separate?
How does gravity affect the speed of diffusion of liquids?

Classroom Activities

Elementary

Middle/High School

Student Resources