Materials

• Plastic eggs (found in grocery or department stores) 
• 1 cup of baking soda
• Food coloring or washable, liquid watercolor paint
• ¼ cup of water 
• Small bowl and spoon for mixing 
• Art tray or cooking tray (that can fit inside a freezer)
• ¼ cup of white vinegar in a bowl 
• Pipettes or medicine droppers

Optional Materials

• 1-2 tsp of dish soap
• Small, plastic figurines 
• Parchment or wax paper
• ¼ cup of water for experimenting

Setting Up 

1. Scoop 1 cup of baking soda into a mixing bowl (this should be enough to fill up 3 standard-size plastic eggs). 
2. Squeeze 3-4 drops of food coloring or watercolor paint into the baking soda. Mix them together until the color is mostly dispersed. (Optional: pour in about 1 tsp of dish soap to create a super bubbly reaction later in the experiment.)
3. Add about ¼ cup of water into the colored baking soda and mix until a solid, moldable paste forms (add more water if it’s crumbly, or add more baking soda if it’s too runny). 
4. Fill one half of a plastic egg with the paste. (Optional: push a small, plastic figurine into the paste.) Fill the other half of the egg with the paste and close the egg shut. Repeat to fill up more eggs.  
5. Carefully re-open the plastic eggs to remove the egg-shaped paste.(see Note under step 6 below).
6. Place each egg-shaped paste on a tray (lined with parchment paper, if you’d like more protection), then place it in the freezer for at least one hour or overnight. 

(Note: It’s extremely difficult to re-open the plastic eggs once the paste freezes inside of them. That’s why we suggest only using the plastic eggs as a molds. If you’d like to freeze the paste inside of a plastic egg, be sure to keep one half of the egg open while it’s in the freezer.)

Experimenting & Observing Together

1. Remove the egg-shaped paste from the freezer, but keep them on the tray (or if you prefer, you can place each frozen paste back into one half of a plastic egg). Encourage your child to touch the frozen paste. Ask, “How does it feel? Is it hot or cold? What’s the texture? Is it smooth? Crumbly? Coarse like sand?
2. Pour about ¼ cup of white vinegar into a small bowl and set it aside. Ask, “What does the vinegar look like? Does it have a color? What does it smell like?” (Optional: fill another small bowl with water to experiment with later.)
3. Time to experiment! Using a pipette or a medicine dropper, squeeze up some vinegar (either model this action for younger children, or have them use a spoon to scoop it up). Squeeze or drip the vinegar over the top of the paste. Ask, “What do you see happening?” Together, discuss what you see, hear, smell, and feel as the baking soda paste reacts with the vinegar. 
4. (Optional) Repeat step 3, but this time squeeze water over the paste. Ask, “How does it compare to vinegar? Is the reaction the same or is it different? How so?”

Baking Soda and Vinegar – What’s Happening?

This colorful experiment lets children observe a safe chemical reaction. A chemical reaction is when two (or more) different substances interact and in the process, change into new substances. This happens at the molecular level. When vinegar is mixed with baking soda, the interaction creates two new substances: carbon dioxide (a safe gas) and water. After the reaction, the baking soda and the vinegar no longer exist as such, and the release of carbon dioxide gas produces all the bubbly fizz. When dish soap is added to the baking soda paste, the fizzing and bubbling reaction is even stronger!