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I have a 10 years old, 4th grader that is interested in using the liquid in a straw as a project. What direction should he go to make a simple project that everyone might understand? Thanks for your time.
Question Date: 2018-02-16
Answer 1:

If the student has learned some geometry, including the volume of a cylinder, maybe he can look at the volume of liquid in different shapes of straws. Another possibility is how fast liquid travels up different types of straws. A third option may be that given a single type of straw, how fast different liquids slide down it on the inside - pure water, olive oil, some kind of solution (such as vinegar). Hope this helps!

Answer 2:

I might suggest you use different widths of straws, insert the straw into the liquid, then put a cap on the straw, and pull the straw out of the liquid. Does the width of the straw affect whether it can hold water inside of it when capped? (answer: it does not, because the area of the air-water contact pushing the water into the straw changes with the width of the straw, so the pressure is the same).

Answer 3:

Can you trick your friends with this straw that doesn’t work? It’s part magic, part science and lots about air pressure.

What you will need:
•2 drinking straws
•A pin
•A glass of drinking water

What you will do:
1 Put a straw in your glass and have a drink of water. What exactly do you do to make the water come up the straw?
2 Now place the other straw on the table and use the pin to punch some holes in the top third of the straw. If there is a pattern on the straw you could use it to hide the holes.
3 Now use the straw with the holes to take a drink of water. How did you go?

What is going on?
When we drink using a straw we suck on the end of the straw while the other end of the straw is in the drink. When we first suck on the straw we suck the air out which means we reduce the air pressure inside the straw. The air pressure outside the straw is then higher so it pushes down on the drink in the cup and forces some of the liquid up the straw. This process keeps going until the drink has reached our mouth, but it is so fast we don’t even think about it!

Monster Challenges:
Can you explain what the holes in the straw do?
• Try using the straw with the holes in it upsided down – with the holes in the drink. What happens? Keep drinking and see if anything changes.
What happens when you blow in the straw? Explaining using what you now know about air pressure.
Could you trick someone with a holey straw? trick straw

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