Seeking easy to understand science facts behind simple experiments

In summary, the conversation discusses various scientific principles used in preschool science activities. These include the pressure of gas inside bubbles causing them to burst, the role of surface tension in creating and popping bubbles, and the effects of density and trapped air on the buoyancy of objects in water. The conversation also highlights the importance of encouraging children to think and predict, rather than just providing them with answers.
  • #1
Blouella
4
0
Hi. I am writing preschool science activities and would like to verify what the scientific principles behind them are.

First example: when you put raisins in clear soda pop, exactly what causes the bubbles around the raisins to pop when they reach the top? Is it only the outside air pressure?

Second example: when you blow through a film of soap to create bubbles, is it surface tension that holds the soap together around the air? And what exactly happens when they pop?

Thank you.
 
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  • #2
Hi Blouella, welcome to Physics Forums!
Blouella said:
Hi. I am writing preschool science activities and would like to verify what the scientific principles behind them are.

First example: when you put raisins in clear soda pop, exactly what causes the bubbles around the raisins to pop when they reach the top? Is it only the outside air pressure?
Yes, this is correct. The pressure of the gas inside the bubble is greater than that of the air so they burst. Soda is bubbled by dissolving highly pressurized CO2 gas in it. The pressure is so high that some of the gas comes out of solution following the bottling (it lives in the little "air" space between the top of the liquid and the bottle cap); it escapes with a "whoosh" upon opening the bottle.
Blouella said:
Second example: when you blow through a film of soap to create bubbles, is it surface tension that holds the soap together around the air? And what exactly happens when they pop?

Thank you.
You are right again, it is surface tension. If you look carefully at a bubble, you will see that fluid tends to distribute from the top of the bubble to the bottom over the space of a few seconds, due to the pull of gravity. Sometimes you even see the start of a drip formi9ng at the bottom as liquid collects there. Eventually the top becomes so thin that it can't support itself and the bubble comes apart--it pops.

Here's another interesting bubble phenomenon. The thickness of the soap film can get very small--comparable to the wavelength of light (of order 1/2 micron, or 5x10^(-7) meters). When this happens you see interference fringes, which look like wavy patterns of color. If the film becomes half the thickness of green light, say, or an integer number times that thickness, then green light reflecting off of the inner and outer surfaces of the film add in phase while other colors reflect out of phase and are suppressed. You see a green reflection. At a different thickness, a different color is favored. So as the bubble thins at top and thickens at bottom, you'll see a progression of color changes. They look wavy and multicolored both because illumination in a typical room is kind of random and because the film thickness is not uniform.
 
  • #3
Thank you Marcus! This is exactly the information I needed.

Here are two more activities that I would like to verify:

What happens, scientifically, when you float two toothpicks in water then dip a straw with dish soap into the water? Or similarly with pepper in water and dish soap?

Also, an orange floats in (enough) water. So does the peel. But the peeled orange sinks. Is this due to air trapped in the peel making it lighter? Or is it a more complicated situation with the orange or the peel or the peeled orange being more or less dense than the water? And if so, what does "density" actually mean?

I hope these questions are not too basic, but these are the things I need to know.

Thanks again.
 
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  • #4
Welcome from me as well.
I have nothing to contribute in the context of this thread, but I want to express how pleased I am that someone is introducing the youngsters to science in a manner appropriate for their age group. PF is all about education, and you will be a pleasing addition.
 
  • #5
Thank you, Danger!

I am writing preschool science books that help children learn the science behind the activity, as you mentioned. It will also encourage them to think and guess (predict) instead of just being "handed" the answers. I believe this develops a measure of common sense thinking, which is sometimes in short supply! ;-)
 
  • #6
An excellent book than you might want to glance at is James Lewis' Learn While you Scrub: Science in the Tub. It's exactly as you would expect from the title.
 
  • #7
I'm late with this but thank you Vanadium. I will definitely start hunting it down.
 

What is the scientific method and why is it important?

The scientific method is a systematic approach to conducting experiments and gathering evidence in order to answer a question or solve a problem. It involves making observations, forming a hypothesis, designing and conducting experiments, analyzing data, and drawing conclusions. It is important because it allows scientists to objectively test and refine their ideas, leading to a better understanding of the world around us.

What are some simple experiments that can be done at home?

There are many simple experiments that can be done at home using everyday materials. Some examples include the classic baking soda and vinegar volcano, making a rainbow with a glass of water, or testing the strength of different types of paper. These experiments can help to demonstrate basic scientific concepts and are a fun way to learn about the world around us.

How do scientists ensure the accuracy of their experiments?

Scientists use a variety of methods to ensure the accuracy of their experiments. This includes carefully controlling variables, using large sample sizes, and conducting multiple trials. They also follow the principles of peer review and reproducibility, where other scientists can review and replicate their experiments to verify the results.

What are some common misconceptions about science?

There are several common misconceptions about science, such as the idea that it always provides absolute truths, or that it is only for geniuses. In reality, science is a constantly evolving process, and while it may not provide absolute truths, it is the best method we have for understanding the world. Additionally, anyone can participate in science and make meaningful contributions, regardless of their intelligence or background.

How can science be made more accessible to the general public?

There are many ways to make science more accessible to the general public. This can include using simple and easy-to-understand language, providing visuals and hands-on activities, and making connections to everyday life. Scientists can also engage with the public through outreach programs, social media, and science communication efforts to help bridge the gap between scientists and the general public.

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