The bulk modulus of water is about 2.2 x 109 Pa, which means that a change of 1 N/m2 of external pressure on the liquid is able to change a given volume of it by a factor of 4.5 x 10-10 (for comparison, the same pressure change would produce a volume change of about 7 x 10-6 for air and 7 x 10-12 for cast steel ). So if we can completely fill a Florence flask with water, we can use it as a hammer to drive a nail into a board!
Objects with a density lower than the fluid that they are submerged in will float; objects with a greater density will sink. This is shown using a brass ball and ping-pong ball of equal size, and a sea of beans.
How it works
500g of navy beans form a rather coarse fluid in a 1.5L glass beaker. Embedded in the beans is a ping pong ball, and sitting on the surface is a brass ball, 4cm in diameter. This fluid needs to have flow 'induced', and this is done by shaking the beaker side to side. The ratio of densities of brass:beans:ping-pong is approximately...
Bread dough is stiff but still flows. A big blob of foodstuff that slumps over time, like Silly Putty but large and edible.
Make bread dough enough for a couple loaves, and knead it stiff enough that a round ball of dough takes half an hour to slump to half its original height. Place on a plate, put a camera on it. Project the image at the beginning, just as the dough ball is released, and again some time later, after viscous flow.
Ice in water at 0°C is strained and added to a room temperature, 50% ethanol in water mixture. Stirred with a temperature probe, the iced mixture reaches -2°C.
The stainless steel temperature probe is connected to a Vernier Labquest Mini and LoggerPro software displays a record of the temperature. Two probes can be used, one in the ice water, and one in the room temperature alcohol.
Instead of beakers, thick walled pint glasses are used. A strainer and bowl are needed for straining the ice from the water, showing that the same ice melting in water at 0°C...
Ethanol and water are mixed in volumetric glassware, showing a volume decrease and a temperature increase.
Two 250 ml graduated cylinders are filled to the line with water and ethanol (100%). A temperature probe shows both at room temperature. The temperature probe is then moved to an empty 500 ml graduated cylinder, and the contents of the two smaller cylinders poured simultaneously to mix well.
The temperature of the mixture rises about 8°C, and the volume decreases to 480 ml just after mixing, clearly visible on the scale of the 500 ml cylinder, and to the class by...
Liquid nitrogen is pumped on and freezes into a sponge of solid nitrogen.
The liquid nitrogen is in a 600 or 800 ml beaker under a shielded bell jar on top of the red vacuum cart. A cold trap is not necessary if only nitrogen is being pumped on.
It is important that the beaker of liquid nitrogen not have frozen water vapor on its side, as the view is impaired. A camera is zoomed in on the beaker, which is in a thick glass bell jar and an acrylic tube shield.
With the pump running and the bell jar vent open, pour the nitrogen and cover the beaker with bell jar. Open up...
A vacuum is drawn over a beaker of sliced cucumber covered in a clear dressing. The cucumber outgases, making bubbles. When the atmosphere is readmitted, the dressing is forced into the cucumber, rendering it translucent and seasoned.
A polycarbonate bell jar with a volume of about three liters is centered on the base, with attention to the seal. The vacuum pump tube ID is the same as the outlet tube OD, so attach by hand. Vacuum release by sliding the vinyl tube off of the outlet.
The vacuum pump is the oil-less variety, and is not bothered by water. The pump is...
Dark red iron[III] solution is rapidly reduced to colorless iron[II] by addition of tin[II] chloride solution, with the rate depending on concentration and temperature.
Four medium footed cylinders are prepared with 100 ml of ferric chloride solution 0.01M with potassium thiocyanate solution added to make the dark red complex. One of the solutions should be hot, so just the iron and thiocyanate solutions in that cylinder, with a 150ml beaker for the demonstrator to fill with hot water from the water cooler, right before the demonstration.
A magnesium ribbon is held with tongs and lit with a match or torch, making a bright flame that consumes the ribbon from the bottom up.
The ribbon should be about 20-30 cm long. Hold the ribbon with the tongs high and at arms length. Let the magnesium ribbon hang at a steep angle but not vertical. Light the bottom of the ribbon by bringing the end of the torch flame up to ribbon. Magnesium will melt before it lights, so carefully with the torch. The ribbon can also be lit with a wooden match.
Wear safety glasses and don't look directly at the flame.
Hydrogen peroxide 30% in a large round flask decomposes to boiling water and oxygen when postassium iodide is added.
The 12L Round Bottom Flask is set on white C-Fold towels covering a large cork ring on the lab bench. 100-150 ml of 30% hydrogen peroxide is carefully poured in. The liquid should be visible against the white towels from the perspective of the class, and any camera, if used.
The catalyst is 5 g of potassium iodide in a small plastic weighing boat labeled KI.
Safety goggles and gloves. Raise the projection screen and make sure the flask is...
Vinegar and two different amounts of baking soda in plastic soda bottles with balloons.
Two 500ml PETN soda bottles of the same make, split a bottle of vinegar between them.
11" balloons are pre-inflated with dry air, with care taken not to stretch the neck of the balloon. Into the balloons with a funnel go one, two teaspoons of baking soday. With 250 ml of vinegar, that's like six liters of gas potential if one carbon dioxide comes from one acid hydrogen ion.
Tap the baking soda powder down away from the neck of the balloon. Stretch the neck and place it over the top...