STEM Activities for Preschool

Easy STEM Activities for Preschool

There is nothing quite as satisfying as watching a preschooler smiling with excitement. Whether they just learned to say a new word or discovered something new, preschool is the perfect place for 2 – 4 year olds to engage and learn. A great way to create such an environment for preschoolers is through STEM activities for kindergarten. Unfortunately, sometimes finding the perfect activity is hard and if it doesn’t work the first time, it can make you want to shrug off the idea altogether. We know you have a lot on your plate and don’t always have the time, which is why we compiled a list of fun STEM projects for preschoolers so you don’t have to. 

What is STEM?

Before we begin, you may be wondering what STEM is. STEM stands for Science, Technology, Engineering and Math. Each of these fields is not only important for child development, but for academic achievement and the workforce as well. Through introducing STEM in early childhood, you will not only get your preschoolers excited, but also spark a curiosity for them to continue exploring STEM fields later on. After sorting through tons of activities, we found the following STEM fun projects to be the best for large groups since they are simple enough for preschoolers to grasp from the start.

1) The Invisible Ink Activity

In this activity, students will write or draw a message that will only appear when grape juice is added. This activity will help demonstrate how acids and bases work. To begin, explain to your class that through the use of a few common house-hold objects, they will be able to write an invisible message that will later be revealed. This activity is best done in partners to students can exchange papers and reveal each other’s secret message at the end.

What you will need to get started:

  • A can or bottle of grape juice depending on your class size, each student only needs a little
  • ⅓ cup baking soda
  • ⅓ cup water
  • Thick paper for all of your students (can be construction paper or a card however, regular paper is too thin to work)
  • 2 small bowls or cups per 2-3 students
  • 2-3 Q-tips per student in case they mess up
  • Paintbrushes for the class
  • Spoons for the class

Instructions to follow with your students:

TIP: Make sure to use a small amount of the baking soda mixture and grape juice. If students use too much liquid, the paper will get drenched and the message will not be revealed.

  1. Pour the baking soda and water into a bowl
  2. Mix the two ingredients together using a spoon
  3. Take a Q-tip and dip it inside the bowl – Be sure not to soak it
  4. Have your students write or draw their message on the paper using Q-tips. Students can either write letters or draw a picture
  5. Wait several minutes for the message to dry. As it dries, it will disappear (if the message does not disappear, students used too much of the mixture and will need to start over)
  6. Have students exchange their papers with a partner
  7. Dip their paintbrushes in a little bit of grape juice
  8. Students will then use the paintbrush to paint over the paper to reveal their partner’s secret message!


Go over the following with your class once the activity is over:

Explain to them that the message was revealed because of two special kinds of chemicals called Acids and Bases. Every liquid is either an acid or base. When mixed together, they have a chemical reaction (known as an acid-base reaction) and together they cause the paper to change color! That is why the secret message appeared once the grape juice was used.

2) The Exploding Lunch Bag

In this activity, students will make a plastic bag explode and learn how chemicals react. You can either demonstrate the activity in front of your class or have students follow the instructions together. The following activity is messy so be sure to clear a surface that can get dirty (you can also do this outside or over a sink!)

What you will need to get started:

  • Small zip-lock bag, one per student
  • 3 teaspoons of baking soda per bag
  • ¼ cup warm water per bag
  • ½ cup vinegar per bag
  • A measuring cup
  • Tissues, one per bag

Instructions to follow with your students:

Tip: Once you add the baking soda to the bag, be sure to work as fast as possible so the chemical reaction occurs.

  1. Pour the warm water into a bag
  2. Add the vinegar
  3. Partially close the bag but leave enough space to add the baking soda 
  4. Put the baking soda into the middle of a tissue (the tissue will help slow down the reaction to give you more time)
  5. Close the tissue around the baking soda
  6. Put the tissue with the baking soda into the bag and quickly zip the bag so that it is fully closed
  7. Put the bag into the sink or down on the ground outside and step back 
  8. The bag will start to expand as the baking soda and vinegar interact and fizzle.
  9. Wait until the bag pops!


Explain the explosion to your students: 

If you mix a large amount of baking soda, which is a base, and vinegar, an acid, into a small surface (i.e. a sandwich bag), the chemicals react and combine to create a gas (Carbon Dioxide) which needs a lot of room. The space the gas needs causes it to continue filling the bag until there is no more room left and then bag explodes.

Since the baking soda is a base and vinegar is an acid, when mixed together, they react chemically. Sound familiar? This concept is also used to create the eruption volcano projects.

3) Shake it Up

The following activity will demonstrate how oil and water do not mix as students combine the two liquids in a jar.

What you will need:

  • Mason Jars for every student
  • Water
  • Food Coloring
  • Vegetable Oil

Instructions to follow with your students:

  1. Have students each fill a Mason jar halfway with water
  2. Then have them add in a few drops (or spoons) of food coloring and mix it until the water changes color
  3. Pour vegetable oil to the top
  4. Have students shake the jar for 5 seconds
  5. Watch the jar while counting to 20.
  6. After about 20 seconds, the two mixtures will stabilize, with the oil staying on top and the water going to the bottom
  7. Have students continue shaking the jar and seeing how the liquids never mix


Explain that oil and water do not mix because oil molecules stick with other oil molecules and water molecules like to stick to other water molecules. Even if the molecules get separated during the mixing, they will still find their way back together. The reason that the oil always stays on top of the water is because oil has a lower density than water. Since water is more dense, it stays at the bottom.

If you would like more STEM activities, be sure to try out Computer Science games for preschoolers. Computer Science contains a blend of all STEM categories because it involves science, technology, engineering and math. Coding is also critical component of Computer Science as it focuses on telling computers what to do. To get your students started with early STEM, have them try out fun programming games for preschoolers such as CodeMonkey Jr. or Scratch Jr. After all, Computer Science and Mathematics remain the only STEM category with more job openings than available students each year!

STEM activities for pre k
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More to explore:

stem kindergarten

Stem lessons for kindergarten

STEM stands for science, technology, engineering, and math. It’s important for children to understand these subjects, or else they won’t be prepared

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