Mixing Forecasts at the Park Sundial Terrace

Three Mixing Tests

A science club met at the sundial terrace in a city park. Members investigated what happened when they mixed familiar food materials. They recorded each material's appearance before mixing and watched for changes afterward. An adult supervised. Students wore safety glasses, used small amounts in open plastic cups, and washed their hands afterward. They did not taste the materials or touch the mixtures.

For the milk test, students placed 20 milliliters of fresh milk into each of three identical cups. They added 5 milliliters of water to one cup and 5 milliliters of white vinegar to another. They added nothing to the third cup. The milk, water, and vinegar were liquids with no visible clumps before mixing. Students stirred each cup for 10 seconds with a separate clean spoon. They kept the cups at the same room temperature and observed them after five minutes. They repeated this comparison three times with fresh materials. In each vinegar mixture, solid clumps appeared in a thinner liquid. The clumps remained after another gentle stir. The other cups stayed smooth. The graph summarizes their results.

For the salt test, students stirred one level teaspoon of salt into 50 milliliters of water. The white grains were no longer visible, and the liquid looked clear. They poured it into a shallow dish. They placed an equal amount of plain water in an identical dish beside it. Both dishes stood at room temperature. Several days later, both dishes were dry. White crystals remained in the salt-mixture dish. No visible solid remained in the plain-water dish.

For the oil test, students combined 10 milliliters of cooking oil and 10 milliliters of water. Before mixing, both were liquids, and neither contained visible solid pieces. After ten seconds of stirring, tiny drops made the mixture look cloudy. After five minutes without stirring, two separate liquid layers appeared. After another gentle stir and five more minutes of rest, the layers appeared again.