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Science is a key player in the future of our children. Theming experiments around holidays encourages a fun creative way to learn. This experiment will help children discover what is viscosity with a fun Valentine’s twist.

The Scientific Method

  • Purpose – What do you want to learn about?
  • Hypothesis – What do you think will happen?
  • Procedure – How will you arrive at your results?
  • Results – What actually happened?
  • Conclusion – Was your hypothesis correct?

Experiment Time

Introduce the Topic- What is Viscosity?

What is viscosity and how does it affect everyday substances? Viscosity refers to how quickly liquids or gasses flow. Some liquids flow more quickly than others, depending on their thickness. Molecules make up all living things. Molecules are the smallest unit of a substance that has all the properties of that substance. Water, for example, is made up of two hydrogen and one oxygen atom, H20. The thicker a liquid is the less likely it will allow something to flow quickly through it. This is because the closer molecules are together, the less they will move around, thus making them thicker or having a higher viscosity. If we pour our liquids from one container to another, some will be more likely to quickly move the candy hearts along, while others will move more slowly. The thinner or less viscous a substance is, the easier it will be for our candy hearts to flow.


  • Crayons/pencils
  • Paper
  • Candy Hearts
  • Water
  • Dish Soap
  • Corn Syrup
  • Lotion
  • Vinegar


Viscosity- is a physical property of a liquid that describes how fast or slowly it will flow

Molecules- the smallest unit of a substance that has all the properties of that substance

Liquid- is a state of matter with a fixed volume but shape adapts to the container it is in

Insert the Scientific Method


To illustrate what viscosity is and how it differs among liquids.


If we pour out different liquids, the candy hearts will move (insert whatever your child thinks will happen). Will they move faster or slower in certain liquids? The idea isn’t to be right, it is to get them thinking critically.


  1. Draw a line graph and label opposite ends: Thick, High Viscosity and Think Low Viscosity
  2. Have clear containers set up with the four different liquids in them: water, corn syrup, dish soap, and glue. If your child is old enough, allow them to pour the liquids into the containers. Ask them about the flow of the liquid- which one flowed quickly?
  3. Have the child gently blow across the surface of the liquids. Which one moves, which one doesn’t? Why?
  4. Place a few candy hearts into each container, gently pour the liquid out and into an empty container. How quickly does it flow from one container to the next? Why does your child think this is happening? Do the candy hearts flow fast or slow with the substance?
  5. If you want to take it a step further, add a few more hearts to see if that changes anything.


Draw and label each jar along your line graph. Which liquids appeared to be more viscous? Have your child define what is viscosity in their own words. Ask your child to think what does this mean about that liquid? Which one was denser?


Did your child prove their hypotheses? Why is viscosity important? Why is it important that water be less viscous? What does this say about the density of a substance? Ask them these questions then ask some more. Just get them thinking and talking about science!

Keep your child’s interest in science going with another fun science experiment: Exploring the World with Science: Water Cycle.

Photo Credit: Ashley W

Sources:, Engineering 4 Kids, Kidzsearch


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