Furthering and expanding our discussion on solubles, the in between liquid and physical state, here is another fun activity to try in the classroom. Solids and liquids are generally easy to recognize. For example, slippery and wet items are usually liquids, like water, liquid soap, even blood. Solids are usually hard and easy to hold like a bowl, spoon, or even dirt. Solids have strong attractions between their molecules that keep them stuck together whereas liquids have some attraction between their particles, but the attraction is more flexible, allowing the particles to slide across each other. It is not always that easy to identify a liquid and a solid when they are happening at the same time. What happens if something is both a liquid and a solid?
In this activity students will explore the differences between a liquid and a solid.
Large Mixing Bowl
Measuring cups (1 cup and ½ cup)
- Pour the cornstarch (1 cup) into the bowl. Identify that it is a solid.
- Add ½ cup water to the bowl with the cornstarch. Identify that it is a solid.
- Mix the mixture, either with a large spoon, but fingers work great too.
- Let students explore the texture, grabbing handfuls and squeezing the mixture and then releasing.
How It Works:
This mixture seems to have both properties of a solid and a liquid simultaneously. This is because when pressure is applied, like when it is squeezed, the particles are forced close together. When the particles are closer together they begin to temporarily attract and attach to each other forming what chemists call “weak intermolecular forces”. What happens when the pressure is released? The solid seems to melt right before your eyes. This is because now the particles are not forced so closely together and are not as attracted and attached to each other and are able to flow like a liquid usually does.
Chemistry is an easy topic to teach to students of all ages, especially elementary school students as they are often very curious about how things change over time. Even looking at the leaves change in the Fall is an example of Chemistry. For more science teaching techniques from the National Science Teachers Association, visit: http://www.nsta.org/about/positions/elementary.aspx or
And for other Fun Learning Science Games, We Invite you to visit any of these pages: