Day 2 - Finish Inquiry Stations from the previous day.
Working with their partner, students will visit 5 stations to test each suction device to see if it will transport a given object across the line on the table. They will have 10 minutes at each station to explore and will record their findings on the 2.2.4-5. Inquiry Stations: Research Notes
| Station | Materials |
|---|---|
| Straw | Lego Man |
| Suction Cups | Cardboard |
| Syringe | Pink Pong Ball |
| Gripper 1 | Water |
| Gripper 2 |
View Organizer: Blank SFM
Teacher will lead students in completing an SFM of the Gripper. The teacher will need to screen capture the completed Gripper SFM, which will be shared with students in week 4.
A 2.2.5 Gripper SFM TEACHER KEY is available for teachers to guide in the lesson.
Class Discussion:
- What scientific principles are at play in the gripper?
- Compare and contrast gripper SFM with organism SFM: What organisms that we researched this week are similar to the gripper? (venn diagram of function?)
- Pros/Limitations of the gripper (what does the gripper not do)
- Is the gripper a muscular hydrostat (instead of muscles use suction)
Teacher Note:
- Scientific Principle of Suction:
- Suction:
- Clamp:
Suction is the principle of physics by which matter is drawn from one space into another because the pressure inside the second space is lower than the pressure in the first.
A force created when there's a difference in air pressure. What is an example of suction? (Vacuum cleaner, straw, suction cup)
A fastening device used to hold or secure objects tightly together to prevent movement or separation through the application of inward pressure. What is an example of a clamp? (Clothespin used to keep a bag shut, locking pliers, vise)
How does a suction cup work?
When a suction cup is sealed against a surface and air is squeezed out of the cup, a low pressure region is created inside the suction area. It's actually the atmospheric pressure OUTSIDE the cup, pressing down on the low pressure area INSIDE the cup, that creates the suction.
How does a straw work?
A straw works because when you sip, you lower the air pressure in your mouth. This causes a decrease in air pressure on the inside of the straw. allowing the atmospheric pressure, which is greater on the outside of the straw, to push the liquid up the straw.
Why does a straw work?
The atmosphere is a massive layer of air. The weight of all that air is constantly pressing on us and on the things around us. At sea level, this invisible pressure is approximately 14.7 pounds per square inch. That is like having the weight of a bowling ball sitting on each square inch or five bowling balls pressing on the liquid filling a two-and-a-half-inch-diameter glass. Put a straw into liquid and the liquid will enter the straw until it reaches the same level as the liquid outside the straw. The liquid in the straw and around it is being pushed down by the air above it in a similar way, so they reach about the same level.
But it gets interesting when you remove some air from the straw. Suddenly, there is less air pressure inside and liquid is pushed up the straw. The more air you remove from the straw, the higher the liquid will be pushed into it. The water will rise until the pressure created by the water column in the straw equals the air pressure difference. If you could create a complete vacuum in your mouth by removing all the air, the water could rise about 30 feet high. It's not possible, however, to create a complete vacuum in the human mouth, so the straw-slurping limit for humans is at a much lower level.
Because you need to push the water up against gravity, it is mainly the difference in height the water needs to overcome that counts, not the total length the water needs to travel in the straw. You can suck up water over a very long distance holding your straw almost horizontally as long as there are no holes along the straw that let air in.
How are vacuums created?
A vacuum can be created by removing air from a space using a vacuum pump or by reducing the pressure using a fast flow of fluid, as in Bernoulli's principle.
How does a vacuum work?
Electric motor that spins a fan, sucking in air – and any small particles caught up in it – and pushing it out the other side, into a bag or a canister, to create the negative pressure.