Kids’ Science: Oil and Watercolor Painting

This delightfully messy activity blends art and kids’ science and is a great way to show that oil and water will not mix.  Don’t let the mess stop you from trying this activity.  My kiddos loved watching the water colors bead up on top of the oil and could have spent the whole morning painting.  And, as a big bonus, this activity isn’t just for the littles, it’s also mesmerizing for older kids too.

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Getting Ready

Prepping for the activity took just a couple of minutes. First, I first gathered my supplies:

• Tray or Baking Sheet with an edge {bigger than my paper}
• Watercolor paper or heavy paper
• Liquid Watercolors or Food Coloring
• Paint Containers
• Eye Droppers or Pipette
• Cooking Oil
• Paper Towels {optional}

I prepped my paints by adding a few squirts of watercolor to each container – saving one container for the oil.  Next, I diluted the watercolor with a couple tablespoons of water and added an eyedropper to each container {including the oil}. Finally, I placed my paper in the tray and got ready for the beautiful mess!

Painting

I showed my 3 and 5 year olds how to suck up the oil using the pipette.  Then I showed them how to make small drops all over their paper.  I knew my 3 year old, Q, would just want to squirt the oil in one spot making a puddle of oil on his paper so I made it a point to demonstrate the process.  As the oil is absorbed into the paper it spreads out, so less is more in this case.

I handed my kids 3 colors that would mix well and allowed them to drip and squeeze as they liked.  They both loved dropping the watercolors on top of the oil and watching as it beaded up.

Q, would just squeeze large squirts in one location making quite a drippy mess and, of course, on this first round I forgot the tray to contain it.

Both kids loved squeezing the pipettes and it was a great way to strengthen those hand muscles for writing.

After making several small puddles on her paper my 5 year old, A, discovered you could suck the color off of the oil.  She was amazed that they really didn’t mix.

When my kiddos were ready for the next paper, I soaked up any huge puddles by gently dabbing them, trying not to remove any color from the paper.  I let the sheet dry for a couple hours before layering them between dry paper towels to soak up any excess oil.  The finished painting are gorgeous and the kids can’t wait to use them in their craft projects.

The Science Behind It

For my 3 year-old, I simply explained that oil and water don’t like each other.  I had my 5 year old pretend to be a water molecule while her father and I were oil molecules.  When my daughter {water} came close to us, we pretended not to like her.  My husband and I hugged saying, “Go away water, we don’t like you!”  They both thought this was hilarious and everyone took turns being oil and water molecules.

For my 5 year old, A,  I explained that oil and water don’t mix for 2 reasons.  First, oil and water have different densities, oil being less dense and water being more dense.  That means for the same volume, there are more water molecules packed in the oil.  We practiced being crowded water molecules and then spread our arms to be less dense oil molecules.  Since oil is less dense it will float on top of water.

The second reason oil and water don’t mix is because of polarity.  Polarity means a molecule has a positive charge at one end and a negative charge at the other.  Water is a polar molecule.  I reminded A that magnets have a positively charged end and a negative charged end.  I then showed her how opposites attract; the positive and negative ends are attracted to each other.

Oil molecules are non-polar and only have a shell of negative charges. Only other polar molecules can dissolve in water because polar molecules dissolve only in polar solvents  and non-polar molecules dissolve only in non-polar solvents.  And so non-polar oil will not dissolve or mix into polar water.

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