activity

Who knew that salad dressing holds the secret to getting oil and water to mix? Learn how to make it happen in this “shaky” experiment. (Plus, make delicious salad dressing!)

safety
  • None
difficulty
  • Beginner
time
  • 25 minutes
  • (plus 1 hour waiting time)

Prepare Ingredients

1 cup plus 2 tablespoons
extra-virgin olive oil
6 tablespoons
red wine vinegar
1 teaspoon
mayonnaise
1 teaspoon
Dijon mustard
Table salt and pepper

Gather Equipment

3
(6- to 8-ounce) clear lidded jars
Masking or painter’s tape
Marker or pen
Measuring spoons
Clock, watch, timer, or other method of keeping track of time
3 per person
spoons
1
 
6 tablespoons
extra-virgin olive oil
2 tablespoons
red wine vinegar

The saying goes that oil and water—like cats and dogs or siblings in the back seat of a car—don’t mix. An easy way to see whether the old saying is true is to use oil and vinegar (vinegar is mostly made of water). Use tape and a marker or pen to label 1 jar as “Control.” Measure your first 6 tablespoons oil and 2 tablespoons vinegar into a glass jar. Screw the lid on tightly. What do the vinegar and oil look like in the jar?

Creating Control Jar

 
2
 

But (spoiler!) there is a way to get oil and water to play nicely. You have to turn them into an emulsion (“ih-MUHL-shun”). Emulsion is a science term for a combination of 2 liquids that don’t usually mix, such as oil and water. An emulsion of oil and vinegar is also called a vinaigrette, which is used as a salad dressing or sauce.

There are a few ways to make an emulsion:

  • You can just mix the liquids together really well through whisking, blending, or vigorous shaking. This breaks the water into teeny tiny droplets that get suspended within the oil. (Plus, you get a great workout at the same time!)
  • You can also add another ingredient called an emulsifier before you mix. Mayonnaise and mustard are examples of emulsifiers: They help the 2 liquids get along better.

Let’s find out which makes a better emulsion: just mixing the liquids really well or adding an emulsifier, too!

 
3
 
6 tablespoons
extra-virgin olive oil
2 tablespoons
red wine vinegar
1 teaspoon
Dijon mustard

Use tape and a marker or pen to label a second jar “Mustard.” Measure the next 6 tablespoons oil, 2 tablespoons vinegar, and the mustard into the jar. Screw the lid on tightly.

 
4
 
6 tablespoons
extra-virgin olive oil
2 tablespoons
red wine vinegar
1 teaspoon
mayonnaise

Use tape and a marker or pen to label a third jar “Mayonnaise.” Measure remaining 6 tablespoons oil, 2 tablespoons vinegar, and the mayonnaise into the jar. Screw the lid on tightly.

 
5
 

Get your arm muscles ready! Make sure the lids are on tight and then vigorously shake 2 jars, 1 in each hand, for 30 seconds. Set the jars aside. (You can also enlist a friend or family member to help. Have the second person shake the 1 remaining jar at the same time.)

Shake the two jars (hard!) for 30 seconds.

 
6
 

Check that the lid is on tight and then immediately start shaking the remaining jar for 30 seconds. Set the jar aside next to the other 2 jars.

What does each jar look like right after you finish shaking it? Can you see layers of oil and vinegar, or does it look emulsified (the same throughout)?

 
7
 

Give each emulsion a taste test. Be sure to use a clean spoon to taste from each jar.

How would you describe the flavor of the different emulsions? Which ones do you like the most?

 
8
 

Now it’s time to see how long each emulsion lasts. Set a timer or watch the clock for 15 minutes. After 15 minutes have passed, check on your emulsions.

 
9
 

Continue to observe your jars every 15 minutes, until 1 hour has passed. Have any of the emulsions separated into layers of oil and vinegar again?

 
10
 

After 1 hour, make one last observation.

 
11
 
Table salt and pepper

Turn your emulsions into a vinaigrette salad dressing by following these steps.

  1. Combine the contents of as many of the jars as you like into a larger airtight container—it’s fine to combine all 3 jars, if you like.
  2. Season your dressing! For each jar you combined, add ¼ teaspoon table salt and ⅛ teaspoon pepper.
  3. Put on the lid and give your new, larger container a good shake to combine everything.
  4. Spoon about 2 tablespoons dressing over your salad.
  5. Save the rest of your dressing for later—it will keep in an airtight container in the refrigerator for up to 1 week. Shake it well before using.

Combining Emulsions

Combine the contents of as many of the jars as you like into a larger airtight container (it's fine to combine all 3 jars).

For each jar you combined, add ¼ teaspoon table salt and ⅛ teaspoon pepper.