Physics 132 Week 7
Density/Pressure
Density Cubes
Each cube has the same volume, but after weighing each one on a scale you can quickly tell that they are different densities. We also have a mass set made with objects that are the same material but different volumes. Use both to introduce density to your students.
Feeling Pressure
Engage your students in a thought experiment about which object would feel the most uncomfortable under an equal force, and then let them feel it to verify their predictions.
**The leather punch has a relatively pointy tip.**
Pascal's Vases
Use this intricate vase to show your students that pressure is solely dependent on depth! Make sure to add a visible dye to the water so that your students can easily see what happens to the entire vessel when you add water to one of the columns.
Pressure and Depth
By allowing water to squirt out of a tall cylinder you can easily show your students how pressure relates to depth, and extrapolate this further to buoyancy and SCUBA diving!
Simple Hydraulic Machine
Two hypodermic syringes attached by a hose create a simple hydraulic machine. Use comparative ratios to explain why this device provide mechanical advantage.
Air Pressure
Atmospheric Pressure
Place suction cups or a rubber mat with a handle on top of a flat surface and have students try to remove it. Or, place two suction cups together and have students try to pull them apart. They will be pleasantly surprised by their results.
Magdeburg Plates
After fitting the two plates together use the hand pump to evacuate the air. Close the valve and detach the pump, then offer $50 to the first student who can pull them apart on their own without turning the valve. And then pop some popcorn!
Atmospheric Can Crush
Place a small amount of water in a can, and boil it on a hot plate. Once steam comes out, invert the can into a cold bath to watch our atmosphere do some work!
Atmosphere Bar
This 1" by 1" steel bar represents the weight of one square inch of atmosphere when held upright.
Thermometers
Thermometers
We have a multitude of thermometers for you to use with your students. (Use a heat lamp or hair dryer to increase temperature)
Constant-Volume Thermometer (Gas), Alcohol Thermometer (Liquid), Galileo's Thermometer (Bouyancy), Bi-metallic Dial Thermometer (Solid), Thermocouple and Galvonometer (Electricity), Liquid Crystal Heat Strips (Thermochromic Liquid), Thermister (Electricity), Black and Decker IR Thermometer (EM Radiation)
Thermal Expansion
Bi-Metallic Strip
When these metals are heated with a blow torch, their different expansion rates cause the metal to bend. Make sure to have a water source on hand in order to cool the metal down before placing it on a surface to rest.
Ball and Ring
Show your students that the ball easily fits through the ring before heating, but after the ball is heated it no longer fits. Make sure to have a water source on hand to cool the heated metal down to fit it back through the ring.
Wire Expansion
When you heat up the wire it expands, loosening the tension on the dial causing it to move. For a more dramatic effect, place the wire directly in the flame.
Gas Laws
Boyle's Law Apparatus
Ask your students to try and compress a syringe with a closed end. They will soon encounter resistance due to Boyle's law, which will give them a physical example to help support your explanation. **Press straight down and minimize any torque**
Steam Gun
This demonstration has some real pop! Show your students that heating a gas causes it to expand, and in a closed system can cause some explosive results.
Fire Syringe
This is another fun and exciting demonstration. After lubricating the piston and maximizing the cotton's surface area, you need to quickly, sharply, and without hesitation compress the piston straight down.
**Do Not Press At An Angle**
Hand Boiler and Pulse Glass
Hold both objects at a 45 degree angle. When heat is applied to the bottom sphere it increases the internal pressure pushing the liquid into the top sphere.
**Do not use a hair dryer for the small hand boiler**
3-D Phase Change Model
This 3-D model shows as much pressure, temperature, and volume information for water as you can fit in a confined area.