Follow

Safety Equipment: Gloves

  • I3-51 CHARLES' LAW - PROJECTION

    I3-51
    Demonstrates Charles' law
    A hollow sphere filled with air is connected by a tube to a pressure gauge on an overhead projector. Place the sphere in ice water (T=273K) and in boiling water (T=373K), and read the pressure for each as well as at room temperature.
    I3, I0

  • I3-52: CONSTANT VOLUME GAS THERMOMETER - ABSOLUTE ZERO

    I3-52
    Determine the value of absolute zero.

    With a constant volume of air in the chamber, measure the pressure P(B) at the boiling point and the pressure P(F) at the freezing point of water. If the pressure P is read at some arbitrary temperature T, then that temperature in degrees celsius is:

    T=100 [P-P(F)] / [P(B)-P(F)]

    For an ideal gas, the pressure should go to zero at the temperature of absolute zero. Setting P=0, the value of absolute zero in degrees celcius can be calculated.

    Another way to do this is to plot a graph of pressure as a function of temperature. Draw the best line through the three points determined at boiling, freezing, and room temperature, and extend it so that it intersects the pressure axis, which is T=0 in celsius degrees.

    Above are photographs of the pressure gauge at each of the three points described.
    I3, I0

    i3-52ai3-52bi3-52c

  • I4-03: LATENT HEAT - ICE TO WATER TO STEAM

    I4-03
    Show latent heat as ice is transformed to water and then to steam.
    A flask is filled to within one inch of the brim with a mixture of water and ice cubes at the freezing temperature of water. The flask is then heated for about 15 to 20 minutes with the burner on high, with the temperature measured by the dial thermometer. If you were to create a plot of temperature as a function of time, it would clearly show that extra heat is required to produce the ice-water and water-steam phase transitions.
    I0

  • I4-11: BOILING AT REDUCED PRESSURE

    I4-11
    Demonstrate that water boils at a lower temperature under reduced pressure.
    Water is boiled in the flask, then heat is removed and the flask is sealed after boiling ceases. Dry ice is packed around the flask, reducing the pressure inside the flask. The boiling immediately resumes.
    I4, I0

  • I4-13: CHANGE OF STATE OF LN - POPPING CAN LID

    I4-13
    Show the increase in volume which accompanies the transition from liquid to gaseous nitrogen.
    Pour a small amount of liquid nitrogen into a can (typically under 10ml) and install the plastic lid. The liquid nitrogen heats up, changes to a gas, and forces the lid open.
    I4

  • I4-14: CHANGE OF STATE WITH BANG

    I4-14
    Demonstrate that the volume of a gas is much greater than the volume of the same amount of liquid.
    Fill the small flask with liquid nitrogen and place the balloon over the top. As the liquid nitrogen turns to gas its volume increases, ultimately bursting the balloon. This is a change of state with a bang, hee, hee, har, har.
    I4, I0

  • I4-15 CONDENSATION OF STEAM - GALLON CAN COLLAPSE

    I4-15
    Illustrates forces produced by the pressure drop when steam condenses into water
    A small amount of water in the can is heated with the lid off, filling the can with steam. The can is then removed from the hot plate and the lid quickly screwed tightly thereon. Within a few seconds the steam begins to condense, creating a low pressure inside the can. The greater atmospheric pressure outside crushes the can.
    I0, SU14

  • I4-17: AIR BALLOON ON LIQUID NITROGEN

    I4-17
    Demonstrate dramatically that the volume of vapor is greater than the volume of the same amount of liquid.
    An air balloon is held on top of a liquid nitrogen bath. The volume of the air balloon decreases for two reasons: first, the volume of the gas shrinks according to Charles' law, and second, some of the air changes to liquid and shrinks considerably. Liquid nitrogen will readily cause oxygen to liquify, and even liquify some of the nitrogen in the balloon.
    I0

    i4-17a

  • I4-19: CONDENSATION OF STEAM - SODA CAN COLLAPSE

    I4-19
    Surprising demonstration using condensation of steam.
    A soda can with a small amount of water in the bottom is heated until the water boils, filling the can with steam. Very quickly the can is removed from the heater and inserted upside down into a container of cold water. The steam condenses so quickly that the can collapses, as seen in the photograph. This is quite a dramatic demonstration, and gets a good reaction from students.
    I4, I0, SU15

  • I4-31 ICE BOMB

    I4-31
    Demonstrates forces created by freezing water
    A pipe elbow with end caps is filled with water, sealed by tightening the ends, and dropped into a metal container of liquid nitrogen. Within about one minute the water freezes, expanding sufficiently to break the cast iron with a loud crack and a big cloud of vapor.
    I0, I4, SU5, OS6

  • I4-51: SUBLIMATION OF DRY ICE - PROJECTION

    I4-51
    Demonstrate sublimation of carbon dioxide (dry ice) from a solid into a gas.
    Place a chunk of dry ice on the plastic sheet, on an overhead projector if desired. As the dry ice evaporates (evaporation sublimation) it becomes smaller but leaves no residue.
    I4, I0

  • I4-52: CARBON DIOXIDE BALLOON ON LIQUID NITROGEN

    I4-52
    Demonstrate condensation sublimation.
    A balloon filled with carbon dioxide gas is held on top of a liquid nitrogen bath. The volume of the balloon decreases for two reasons: (1) the volume of the gas shrinks according to Charles' law, and (2) the boiling point of carbon dioxide is well above that of nitrogen, so the carbon dioxide condenses, forming dry ice powder. The small granules of dry ice, which can be easily seen in the deflated balloon, disappear as the balloon warms up and inflates once again.

    i4-52a

  • I5-15: ADIABATIC EXPANSION OF CARBON DIOXIDE

    I5-15
    Illustrate adiabatic cooling by producing dry ice
    Carbon dioxide, leaked slowly out of the fire extinguisher onto a black felt cloth, produces dry ice, which can be easily seen. Adiabatic expansion and cooling occur when the CO2 gas comes out of the nozzle under high pressure and expands in the atmosphere. Enough is produced to pass the cloth around the class so that students can feel that it is actually cold. This experiment is a bit more complicated than simple adiabatic expansion. The carbon dioxide actually exists in the fire extinguisher as a liquid, so that much of the cooling is due to the evaporation of the liquid CO2 before it is ejected from the nozzle.
    FS1

  • I5-31 STEAM ENGINE - STATIONARY

    I5-31
    Working model of a steam engine
    The engine can be attached to a weight hanging by a string over an axle which is connected to the engine through a series of gears.
    I5

  • I5-32: STIRLING ENGINE

    I5-32
    Demonstrates a Stirling engine
    The Stirling engine is a closed-cycle regenerating heat engine using an external heat source. Air expands when heated, driving the piston, which drives the flywheel and forces cool air into the chamber for reheating. Heating the heat sink on the engine starts the flywheel rotating.

    Safety note: Please make very certain that fuel tank is fully closed when finished.
    I5

  • I5-41: ENDOTHERMIC REACTION - ENTROPY

    I5-41
    Aid a discussion of entropy.
    31.5 grams of barium hydroxide and 15.2 grams of ammonium thiocyanate, both solid powders initially at room temperature, are mixed. As they are stirred using the digital thermometer probe a chemical reaction occurs, producing water with barium cyanate and ammonium, both of which are soluble in the water. The solution becomes very cold, and can freeze a wettened wooden block to the bottom of the beaker.

    This experiment can be described in terms of entropy using two approaches: (1) As the mixture cools, it must become a liquid, increasing its disorder so that entropy will increase, or (2) The tendency toward disorder drives the reaction, creating the liquid reaction product.

    Note: PLEASE CALL THE LECTURE DEMONSTRATION GROUP AT 405-5995 NOT LATER THAN THE MORNING BEFORE YOUR REQUEST SO THAT WE HAVE THE TIME TO PREPARE THE NEEDED CHEMICALS.

  • I5-51: SPECIFIC HEAT - ALUMINUM AND COPPER

    I5-51
    Illustrate calorimitry and to determine experimentally the specific heats of aluminum and of copper.
    Boil the aluminum and copper blocks in a pan of water and place the metal blocks at 100 degrees C into equal amounts of water at room temperature in two styrofoam containers. Stir the water in the containers with the digital thermometer probe, measuring the temperature when equilibrium is reached. From these measurements the specific heats can be determined.

    Multiply the specific heat by the molar mass to find the molar specific heat. The values for both materials are nearly the same and equal to 3R=6(1/2)kT.
    I5, I0, ME1

  • I6-02: NITROGEN DIAMETER AND MEAN FREE PATH

    I6-02
    Experimentally determine the diameter of the nitrogen molecule and to determine the order of magnitude of the mean free path of nitrogen gas molecules at STP.

    Using the pan balance pour 700 cm3 of liquid nitrogen and demonstrate that it has a mass of about 560 grams. The mass of the dewar is about 421 grams. For liquid nitrogen the volume per molecule can then be determined to be

    Vol/Mol=700 cm3/[(560g)/(28g/mole)(1mole/6.0x1023molecules)]=5.8x10-23cm3.

    Assume molecule is a cube, so d = 3.9x10-8 cm.

    Volume per molecule @ STP = 22.4x103 cm3 / 6.0 x 1023 = 3.7x10-20 cm3

    Mean free path = V/d2 = 3.7x10-20 cm3 / (3.9x10-8 cm)2 = 2x10-5 cm.
    I6, I0, ME1

    i6-02a

  • I6-24: DIFFUSION VELOCITY

    I6-24
    Show that the diffusion velocity is proportional to the RMS molecular velocity.
    Cotton swabs dipped into HCl and NH4OH respectively are inserted into the ends of the tube. HCl gas (molecular weight 36.5) and NH3 or ammonia gas (molecular weight 17) begin to diffuse inward. In less than 25 minutes they meet, forming a ring of ammonium chloride (NH4Cl). The diffusion velocity is proportional inversely to the square root of the molecular mass, because according to equipartition of energy the average molecular speed is inversely proportional to the square root of the molecular mass. This means that the distances traveled by each vapor before they meet are in the proportion:

    d(NH3):d(HCl)=SQRT(36.5/17)=3:2 approximately.

    Use caution when handling chemicals. Always wear protective gloves. Please do not throw used swabs in garbage; place in included water beaker instead for proper disposal.

  • I7-21: SUPERCONDUCTOR - MAGNET LEVITATION

    I7-21
    Demonstrate levitation of a magnet above a high-temperature superconductor
    A one-inch diameter superconducting disc is set on a conducting base in a bath of liquid nitrogen. A cubic samarium cobalt magnet levitates above the superconductor. Note that to show the Meissner effect you must place the magnet on the disc before cooling it down. When the superconductor passes through its transition temperature the magnet rises up by itself and levitates. For large groups, a camera can be provided.
    I7, I0