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Pressure in fluids
These resources explore pressure through investigation. The list provides a range of activities, lesson ideas, background information, practical tips and suggested teaching strategies. and links to the following areas of the 2014 National Curriculum:
• atmospheric pressure, decreases with increase of height as weight of air above decreases with height • pressure in liquids, increasing with depth; upthrust effects, floating and sinking • pressure measured by ratio of force over area – acting normal to any surface
Visit the secondary science webpage to access all lists: www.nationalstemcentre.org.uk/secondaryscience
Machines 11-14
Quality Assured Category: Science Publisher: Institute of Physics: Supporting Physics Teaching
This whole suite of materials is good, but of particular relevance to this topic are the first three activities in the second unit; What’s in Pressure? You’ll find lesson plans in document Teaching Appraoches. Background information and teacher guidance are available in Physics Narrative and Teaching and Learning sections.
Having “played” with a tray of marbles in the first activity, students should develop quite a sophisticated understanding of pressure at a particulate level. They then go on to apply their ideas, thinking about the relationship between pressure, force and area before feeling the forces for themselves with a pair of syringes. Teachers will be able to assess students' understanding of this topic by asking them to draw diagrams showing the moving particles inside the syringes.
Vacuum Bazooka
Quality Assured Category: Science Publisher: whynotchemeng
The bazooka demonstration is great fun but its real value is in helping students to appreciate the forces and pressures that cause the movement. So long as your school has a vacuum cleaner, your technician should be able to put the equipment together fairly easily – just make sure the tube is the right diameter.
Demonstrating Physics: Forces
Quality Assured Category: Science Publisher: Teachers TV
There are a couple of demonstrations included on this film which fit snugly into this topic.
Expanding Marshmallows starts about 3½ min into the film and shows how the air trapped inside marshmallows will expand significantly if the air pressure outside is reduced, it’s a great demonstration.
It is also an experiment that can be carried out quickly and easily by students using small marshmallows (the type used on top of hot drinks) and 10 or 20cm3 plastic syringes.
1. After removing the plunger, put the marshmallow into the syringe.
2. Replace the plunger and gently push it up until it is just below the marshmallow.
3. Putting the finger over the open end of the syringe, pull down on the plunger whilst observing the marshmallow expand.
4. The marshmallow shrinks rapidly when the finger is removed.
5. Similarly, using the plunger to compress a syringe full of air will shrink the marshmallow and it will now expand when the finger is removed.
The Cartesian Diver starts about 8½ min into the film and it is excellent for showing the effect of pressure in liquids. It’s good to demonstrate it with a test tube inside a two litre bottle so that students can see the air bubble changing size. Once they've seen this they could carry out the experiment for themselves, perhaps using sauce sachets which are easier to handle than the tubes.
Physics for Non-Physicists: Forces
Quality Assured Category: Physics Publisher: Teachers TV
Significant numbers of students will find the two demonstrations in this film counter-intuitive and that’s exactly why you should consider using them with your classes. The film shows a specialist from the Institute of Physics running some training for science teachers who are then seen trying the ideas out in their own classrooms.
The air bubbles demonstration (about 7 min into the film) takes a phenomenon that students will have seen many, many times; bubbles moving floating upwards in a liquid, and slows it down by using glycerol (propan-1,2,3-triol) in place of water. Challenging students to predict whether the smaller or larger bubbles will reach the top first is straightforward but asking them to give a give a reason will really put their ideas to the test. Encourage the use of physics terms and notice how the syringe has been set up to provide a good supply of bubbles.
Demonstrating Physics: Electrostatics
Ignore the fact that this film is entitled Electrostatics and fast forward to 12 min into the film. This is a fantastic, and really quick, demonstration that brings home what determines whether something will float or sink. Just make sure the students don’t really think that the metal ball turns into a polystyrene one!
Air Pressure
Quality Assured Category: Science Publisher: Gatsby Charitable Foundation
This is a linked pair of demonstrations which show how large forces can arise when atmospheric pressure is unbalanced. What's particularly useful is the explanation of why the crushed can demonstration may be confusing for students and how the second demonstration can be used to more clearly illustrate the effect of air pressure.
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Water Pressure With Water Bottle Experiment
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Kids will love learning about how water pressure changes with depth in this Water Pressure With Water Bottle Experiment. This can even be used to explain the force that water pressure has on deep-sea divers and scuba divers too!
Get more fun and easy Weather Experiments for Kids here!
The best thing about this cool experiment is how simple and easy it is to do with household items you already have!
Table of Contents
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Supplies Needed:
- Clear Plastic Bottle or Plastic Cup
- A Sharp Nail or Screw
- Food Coloring (Optional)
How to Discover the Science of Water Pressure
- Poke a few holes at different heights on a bottle or cup.
- Pour water into the bottle (Add food coloring if desired).
- Pay attention to which holes in the bottle spray water out with the most force.
Step 1: Poke 3 Holes In a Bottle
I like to use a large 2-liter bottle for this experiment, but even a smaller water bottle will work too. Make sure the label is removed from the bottle and it is nice and clean before creating the holes in your bottle.
Then using a sharp nail or screw, and with adult supervision, carefully poke 3 holes at different levels on the bottle.
I usually poke one hole about an inch from the bottom of the bottle, another in the middle, and the last hole a little bit closer to the top of the bottle.
Step 2: Fill The Bottle With Water
Adding food coloring to the water will add to the visual display of your experiment, but you may want to skip this option if you are worried about your little ones making a mess with it.
If you do add some food coloring to the water, it’s easiest and the least messy to mix it into a bowl of water before pouring it into the bottle.
Use a funnel and pour enough water into your bottle to fill it all the way to the top. It might be helpful to have someone else plug the holes on the bottle with their fingers to keep the water from leaking out while filling it up.
Also, don’t forget to put a large pan underneath the bottle to prevent water from spilling and spraying everywhere!
You will also want to put a large bowl upside down in the pan and use it as a platform to set your bottle up a little higher (you will see why this is important in the next step).
Step 3: Watch The Water Spray Out of The Holes at Different Levels
Now it’s time to release the water from the bottle and watch what happens! Which hole do you think the water will shoot the farthest out of!!?
You may want to have some extra water to keep pouring into the top of the bottle to keep the water level high enough to flow out of all three holes.
If you guessed that the hole closest to the bottom of the bottle would shoot water the farthest, you were right!
Now it’s time to find out what makes the water shoot so far out on the bottom hole and not very far out of the top hole!
Water Pressure Experiment Explanation
As we saw in this experiment, the hole that has the most water above it, shot water out the farthest and with the most force! This is because as the water depth increases, the water pressure increases!
Water pressure is created from the weight of the water pushing down on an object or a surface. Water is very heavy and dense, so the deeper underwater you go, the more weight, or pressure you will feel.
Another type of pressure is air pressure. Believe it or not, the gases that make up the air around us actually do weigh something! To learn more about air pressure, check out this Water Bottle With Holes Experiment .
Our Earth is covered with a layer of air that is about 80 miles thick called the atmosphere. The entire atmosphere which is a whopping 80 miles thick has the same pressure as being below only about 30 feet of water.
Because water is much more dense than water it makes sense that it only takes a water column 30 feet deep to create the same pressure as 80 miles of air on top of you right!?
This is why scuba divers have to train and prepare carefully before diving deep into the depths of the ocean!
If they don’t train properly and use the right equipment, the extreme water pressure can cause them to have major health issues.
More Fun Science Experiments for Kids:
- Color Changing Milk Experiment
- Light Refraction in Water
- Rising Water Experiment Step by Step
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