Salad Dressings and Density of Fluids

A salad dressing always heightens the taste of a salad. The simplest salad dressing is oil, vinegar, salt, and pepper. You could add honey to sweeten it or some dijon mustard. Have you noticed that when you pour oil and vinegar, they do not mix? Have you ever wondered why?

Salad dressing reciipes1 (1)

Salad dressing reciipes1 (2)

I had written about density in my previous blog – Float or Sink, but here is a recap. Density is how much ‘stuff’ is packed in a certain volume. The density of a liquid is the mass per unit volume (1kg/m3). For all practical purposes, if you take 1 liter of liquid and measure the mass (weight on earth), the density of that liquid (for example) 1.2 Kgs, then the density of that liquid is 1.2/1 =1.2.

Here is an easy and fun experiment to do with kids about the density of liquids. If you color the liquids, it would be a fun addition to their room.

Use the same volume of liquids. I used 1/4 cup each.

The liquids I used were honey, vegetable oil, water, dish soap, and milk. I had to use a baster and add milk gently which I did not and it did not work, so I redid the experiment without milk. You can also add vinegar.

Ingredients:

  • 1/4 cup honey
  • 1/4 cup vegetable oil (you could mix an oil based food coloring)
  • 1/4 cup water mixed with some water-based food colour
  • 1/4 cup dish soap
  • a tall glass
  • cherry and other small objects

 

Directions:

Pour equal volume of the different liquids in cups and place them in order of liquids being added. (honey, dish soap, water, and vegetable oil.  I also labeled the cups.

Pour the honey carefully into the cup without touching the sides of the cup. Carefully add dish soap. If you have a baster, use that.

Then add water and then vegetable oil. It is ok if it mixes a little.

Leave it for an hour to settle, you will see the different layers.

Why does this happen? Liquids have different densities. The heavier liquids like honey have a higher density and therefore will sink below the lighter liquids.

Screenshot 2018-10-21 at 8.58.47 PM

The same rule for float or sink works here too. Denser solids will sink and solids that are less dense like a walnut will float. A cherry is denser than water and oil so it settles on top of the honey. Try different objects, how about a ping pong ball. Experiment with different liquids like vinegar, baby oil, lamp oil, corn syrup or maple syrup. Ask your child to hypothesize and then document the results.

20181016_151340
Adding solids to the liquids

 

 

 

 

 

 

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Published by

chaiwithpreethi

Daughter, Wife, Mother, Teacher, Student! Love to cook and bake, eat and travel. Continue to learn!

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