Fizzy Volcano Cups

What you need

• Baking soda, 2 tbsp per cup
• White vinegar, 1/2 cup
• Clear cups, 3
• Tray
• Dish soap, a squirt (optional)
• Food coloring (optional)
• Bowl, 1, for the baking soda
• Spoon, 1
• Towel, 1, to go under the tray
• Small cup, 1, for pouring the vinegar

How to do it

Grown-up prep: Put the cups on a tray to catch the overflow. Pre-measure the vinegar into a pourable cup so little hands only pour, not measure from the bottle.

1. Line up three cups on the tray and give each one a name.
2. Spoon baking soda into the cups: one spoon, then two, then three.
3. Add a squirt of dish soap and a drop of color to each cup, if you have them.
4. Say the scientist rule together: faces back from the cups!
   Ask: Which cup do you think will erupt the most?
5. Pour a little vinegar into the first cup and step back.
6. Pour the same amount of vinegar into the other cups, and compare.
   Ask: Which cup made the biggest eruption? Why?
7. Count the seconds each eruption lasts.
8. Add more baking soda to a cup and make it erupt again!
9. Show someone your biggest eruption, and plan an even bigger one for next time!
   Ask: What could make the next volcano even bigger?

Play it again

• Color race: every cup gets a different color, and the color that climbs highest wins.
• Mystery cup: a grown-up secretly leaves the baking soda out of one cup. Can you find the dud?
• Lemon volcano: try lemon juice instead of vinegar and compare the fizz.