Create Hot and Cold Bubbles

Materials you'll need

• 1 empty plastic bottle
• Bubble solution
• Shallow plate or dish
• 2 glasses of water
• Blue food coloring
• Red food coloring

 

Step-by-step tutorial

Step 1: Fill one glass with cold water and add a few drops of blue food coloring. Fill a second glass with hot water and add a few drops of red food coloring.

Step 2: Pour bubble solution onto a shallow plate. Dip the mouth of your bottle into the solution so the opening gets fully coated.

Step 3: Place the bottle into the glass of hot (red) water. Watch the mouth of the bottle. A bubble will slowly grow from the opening.

Step 4: Repeat with the cold (blue) water. This time, the bubble shrinks.

Step 5: Try both glasses side by side to compare — warm grows a bubble, cold doesn't. Warm goes up, cold goes down.

Learn more

The secret is in the air trapped inside the bottle. When the bottle sits in hot water, the air inside heats up, and warm air expands — its molecules speed up and spread out, taking up more space. That extra air has to go somewhere, so it pushes out through the bubble solution and inflates a bubble. In cold water, the opposite happens: the air cools down, its molecules slow and squeeze together, and the air contracts — not enough pressure to push out a bubble. This is the same reason warm air rises and cold air sinks in the atmosphere, creating wind and weather all around us.