Hot and Cold Bubbles
Concepts and skills: States of matter, surface tension, evaporation, temperature, experimental design, data collection, compare and contrast
Recommended ages: 4 and up (with assistance)
Materials:
1 cup warm water
2 tablespoons dish soap
2 tablespoons sugar
Bowl and spoon
3 or more identical small clear jars or food storage containers with lids
Masking tape or sticker labels and pen
Measuring spoons
Clock or watch
Paper
What to do: Pour the warm water into the bowl. Add the sugar and stir until dissolved, then add the dish soap and stir until mixed. This will be your bubble solution! Let sit while you set up the jars.
Choose three or more locations that are different temperatures. Examples could include outdoors, indoors next to a heating vent, in the refrigerator or in the freezer. Label each jar or container with a location using a label or a piece of tape. Using a measuring spoon, add the same amount of bubble solution to each jar. (The amount you use will depend on how large your jars are.) You want enough solution to totally wet the inside of the jar and form as many bubbles as possible, plus a little liquid remaining at the bottom. Let them sit long enough to reach the temperature (30 minutes or more).
Decide how long you would like to shake each jar (at least 10 seconds is recommended). Using one jar at a time, shake it for the set amount of time using the clock or watch, set the jar on a flat surface, and time how long it takes for all the bubbles in the jar to pop. Create a table on the piece of paper to record the location and time it took the bubbles to pop. Repeat with the other jars.
Extension: You can use a thermometer to measure the temperature of the bubble solution in each jar, and create a graph of temperature vs. length of time your bubbles lasted. Label each point with the location.
Additional information: Soap bubbles will pop more quickly when warm. When you increase the temperature of the bubble solution, the molecules in the liquid and the gas inside the bubble are moving more quickly, causing the solution to thin faster and be more likely to pop. The warm temperature also causes the film that forms the bubble to evaporate more quickly, causing it to pop. However, because the air in the closed jars will become more humid, it can have the opposite effect by slowing the rate of evaporation, and molecules can also return to the bubble from moist air, reducing the rate at which the bubbles will pop. This is why it is important to keep the lids on all the jars so that this is held constant.
Bubbles last longer in cold weather because the liquid in the bubble is slower to evaporate, but if it is too cold, the soap in the bubble solution becomes insoluble in water and doesn’t form the film needed to make bubbles. Also, surface tension of the solution increases as temperature decreases, and higher surface tension makes it harder for bubbles to form.
Catching Bubbles
Concepts and skills: surface tension, hydrophilic and hydrophobic surfaces, fine motor skills, recording observations
Recommended ages: 6 and up
Materials:
Bubble solution (or, 1/2 cup warm water, 1 tablespoon sugar, and 1 tablespoon dish soap)
Bowl (if you make your own bubble solution)
Bubble wand
Different materials to test: aluminum foil, waxed paper, paper, plastic wrap, tables, countertops, baking sheets, gallon plastic bag, wood, etc.
Pen or pencil and paper
Water
Paper towels
What to do: If making your own bubble solution: Pour the warm water into the bowl, then add the sugar and stir until dissolved. Add the dish soap and stir lightly until mixed.
Create a table on the piece of paper that lists each material you will test, along with columns for the bare surface, surface with water, and surface with bubble solution. Cut pieces of foil, wax paper, and plastic wrap. Lay out different materials to test on a flat surface. Dip the bubble wand in the bubble solution and very gently blow some bubbles onto the first material, trying to get bubbles to land on it and not blow past it. Observe what happens to the bubbles and write if they pop or not in the table. Repeat by blowing bubbles onto each material and filling out the table. Which material could “catch” the bubbles without them popping?
Wet a paper towel in water, and wipe a thin layer of water onto each surface. Try blowing bubbles onto each surface again and record your observations. What’s happening to the bubbles now?
Dip a new paper towel into the bubble solution, and wipe a thin layer of it onto each surface. Try blowing bubbles onto each surface again and record your observations.
Additional Information: Whether a bubble pops when it comes in contact with a solid surface depends on many different factors, including the surface properties of the material. Surfaces can be hydrophobic (repel water), which means water will bead up, or hydrophilic (attract water), meaning water will spread out in thin sheets. This is due to a material’s surface roughness, and even surfaces that look and feel smooth to you might have very tiny bumps or pores. These can actually help the material repel water because water is held together by surface tension, and thereby unable to penetrate into the tiny gaps in the material. Other materials such as paper or sponges have larger gaps that help then absorb water.
When all your materials were dry, you probably found smooth, waterproof surfaces like waxed paper, plastic wrap and aluminum foil did the best job catching bubbles. Materials that absorb water, such as paper, probably caused the bubbles to pop because they quickly soaked up the water in the bubble. Other seemingly smooth, waterproof surfaces might have caused bubbles to pop due to very tiny bumps or pores on their surface.
When you got the surfaces wet, especially with soapy water, it should have become much easier to catch the bubbles. The water forms a thin film on top of the solid surface, preventing the bubble from touching the solid directly. This can greatly extend how long it lasts.
