Coke versus Diet Coke Density Demo

This demonstration reviews the concept of density. It examines why certain objects float or sink in water and highlights some interesting information about cola versus diet cola soft drinks.

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This demo is part of the STAO demo collection.  Click here to check out all of them.

Stacking Liquids – Scientific American

A stratified science project from Science Buddies

By Science Buddies on May 26

You can stack books and stack blocks, but did you know you can also stack liquids? See if you can build your own liquid rainbow–in a single cup!  Credit: George Retseck

Concepts:Physics Chemistry Density Liquids

Introduction

You probably know that when solid objects are placed in liquid, they can sink or float. But did you know that liquids can also sink or float? In fact, it is possible to stack different layers of liquids on top of one another. The key is that all the different layers must have different densities. You can stack them by picking several liquids with a range of densities or by varying the density of one liquid by adding chemicals such as sugar or salt to it. If you choose colored liquids or add food coloring to each layer, you can even create a whole rainbow of colors in one single glass! Want to see for yourself? In this science activity you will stack several liquids—one by one—and create a colorful density column!

Click here for more details Source: Stacking Liquids – Scientific American

Don’t Keep Your Hot Water Bottled Up

Two thermometers

Hot water rises because its molecules are moving rapidly as they expand the water.  Hot water is less dense, therefore, the same amount of water takes up the larger space. Hot water rises above the colder denser water.  The resulting movement is called convection.  The flowing displacement of a mass of cold fluid under large amounts of hotter fluid is the same phenomena seen with weather patterns where cold higher pressure air displaces and pushes up the hotter air. Hot air balloons also take advantage of this squeezing action.

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Which Grape is Heavier?

Floating grape

Students should already have had some previous experiences with solids and liquids.  This activity allows the students a chance to observe buoyancy and interactions of solids with liquids.  They can investigate and describe the properties of density, as well as adhesive/cohesive forces. The usage of common table foods creates high interest.

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