What happens when you mix sugar and water

What happens when you combine blue, green, yellow, and red water in a single glass? Brown, right? Not necessarily! Make this mesmerizing rainbow in a glass by experimenting with water density.

Density measures the amount of mass in a particular space. For example, oil molecules are packed less tightly than water molecules, making oil less dense than water and causing it to float on top when the two are combined. Water can have different densities as well. An easy way to change water density is with sugar. When you mix sugar with water, the sugar molecules occupy the space between the water molecules, making the solution more tightly packed (denser). The more sugar you add, the denser the solution.

In this sugar water density experiment, we will change the density of different colored water solutions so that they stay separated from each other. All you need are a few common household items.

Supplies

• 5 drinking glasses
• Warm water
• Sugar
• Spoon
• Food coloring in four different colors
• Small turkey baster

How to Conduct the Sugar Water Density Experiment

1. Fill four drinking glasses with 1/4 cup of warm water each.

2. Add sugar and food coloring to the water. Each color will have a different amount of sugar in it.

Glass 1: Add 1 tablespoon of sugar and 2 drops of red food coloring. Stir vigorously to completely dissolve the sugar.

Glass 2: Add 2 tablespoons of sugar and 2 drops of yellow food coloring. Stir vigorously.

Glass 3: Add 3 tablespoons of sugar and 2 drops of green food coloring and stir.

Glass 4: Add 4 tablespoons of sugar and 2 drops of blue food coloring and stir.

NOTE: Stirring to completely dissolve the sugar is very important. Without the sugar fully incorporated into the water, you’ll have trouble getting the colors to separate. Heat up your water if it’s not working—five to 10 seconds in the microwave and an extra stirring session should help.

3. Use the turkey baster to transfer about half of the blue water into the empty glass. This is where you’ll make your rainbow.

4. Still using the baster, transfer half the green water into the rainbow glass. Add it slowly on top of the blue water. It should sit on top.

5. Add the yellow, and then the red. You’ll see a beautiful rainbow!

NOTE:  Make sure the sugar is completely dissolved before attempting to layer the colors—it’s what creates the difference in density of each color.

Bring on the Science!

During this activity, natural questions may come up.  If they don’t, start a discussion using the questions below!

Is dissolving sugar in water an example of a chemical or physical change? This process is a little trickier to understand than most, but if you look at the definition of chemical and physical changes, you'll see how it works. Here are the answer and an explanation of the process.

Relating Dissolution to Change

Dissolving sugar in water is an example of a physical change. Here's why: A chemical change produces new chemical products. In order for sugar in water to be a chemical change, something new would need to result. A chemical reaction would have to occur. However, mixing sugar and water simply produces... sugar in water! The substances change form, but not their identity. That's a physical change.

One way to identify some physical changes (not all) is to ask whether the starting materials or reactants have the same chemical identity as the ending materials or products. If you evaporate the water from a sugar-water solution, you're left with sugar.

Whether Dissolving Is a Chemical or Physical Change

Any time you dissolve a covalent compound like sugar, you're looking at a physical change. The molecules get further apart in the solvent, but they don't change.

However, there's a dispute about whether dissolving an ionic compound (like salt) is a chemical or physical change because a chemical reaction does occur, where the salt breaks into its component ions (sodium and chloride) in water. The ions display different properties from the original compound. That indicates a chemical change. On the other hand, if you evaporate the water, you're left with salt. That seems consistent with a physical change. There are valid arguments for both answers, so if you're ever asked about it on a test, be prepared to explain yourself.

Cite this Article

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Your Citation

Helmenstine, Anne Marie, Ph.D. "Dissolving Sugar in Water: Chemical or Physical Change?" ThoughtCo. https://www.thoughtco.com/dissolving-sugar-water-chemical-physical-change-608347 (accessed January 2, 2023).

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