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Thermal Properties of Matter

  • I3-33 HELIUM BALLOON ON LIQUID NITROGEN

    I3-33
    Demonstrates how a gas contracts when cooled
    A helium balloon which is cooled by resting on a liquid nitrogen bath becomes becomes more dense -- by about a factor of 4. When the balloon is removed from the liquid nitrogen it warms up, expands, and floats away, unless it is tethered
    I0, FS1

    I3-33A

  • I3-35: SOLAR BAG

    I3-35
    To demonstrate how the density of a gas changes with temperature.
    This is a large bag that will float when the air inside is heated. On a sunny but cool day, unroll the solar bag outside in the shade and fill it with cool air. Tie off the open end. Tie the string to the tied-off end, and move the bag into direct sunlight. The solar bag will soon float as the air inside heats up and expands. Obviously, this demonstration is primarily suited to outreach programs held out-of-doors, not to classroom use.
    I3

  • 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

  • I4-16: DRINKING BIRD

    I4-16
    Stimulate thought about heat exchange and liquid-vapor phase transitions.
    The bird's head and beak are initially wetted, and the bird positioned so that its beak will dip into the water cup when it tips (whether or not the cup is there). The liquid sealed in the glass chamber is reported to be tri-chloro-mono-fluoro methane.
    I4

  • 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

  • I4-18: PULSE GLASS

    I4-18
    Illustrate change of phase between liquid and vapor in an confined fluid.
    Hold the pulse glass so that the bulbs point up, and enclose one bulb with your hand to warm it. The heat from your hand will change some of the liquid on that end to vapor, increasing the pressure in that end and forcing the liquid into the other end.
    I4

    i4-18a

  • 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

  • I4-33: CRYOPHORUS

    I4-33
    Illustrate freezing caused by cooling by evaporation.
    Insert the lower end of the cryophorus into a liquid nitrogen bath, with the water in the sphere at the upper end. The liquid nitrogen will reduce the pressure inside the tube, causing evaporation of some of the water from the upper sphere. After sufficient cooling during the evaporation process, the remaining water in the upper sphere freezes.

    The photographs above show the water (left) before dipping the tube into LN and the ice (right) in the cryophorus tube.
    I4, I0

    i4-33ai4-33b

  • I4-34: HAND WARMER

    I4-34
    Demonstrate the heat of fusion.
    A plastic bag contains a supersaturated solution of sodium acetate. When fusion is commenced by clicking a metal disc in the solution or by some other shock, the liquid quickly becomes solid, producing a large amount of heat.
    I4, I0

    i4-34a

  • I4-35: LOWERING THE FREEZING POINT OF WATER USING SALT

    I4-35
    Demonstrate that the freezing point of water can be reduced by putting ice in a salt water bath.
    The temperature of an ice and water mixture is measured with a digital thermometer. Adding salt to the icewater mixture reduces its temperature. The thermometer can be used to stir the mixture. By this technique the freezing point can be lowered as much as 15 degrees celcius.
    I4

    i4-35a

  • I4-36: REGELATION - ICE UNDER PRESSURE

    I4-36
    Demonstrate regelation.
    A thin wire with weights on the ends is looped over an ice cube. In a few minutes the wire will cut through the ice cube and the weights fall with a bang onto the stand. The ice re-freezes after the wire passes, leaving a single cube of ice. The photograph above shows the wire cutting through the ice cube.

    i4-36a

  • 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

  • I4-61: BINARY PHASE TRANSITION - CRITICAL OPALESCENCE

    I4-61
    Show the behavior of a binary fluid as it passes through the critical temperature.
    A small sealed vial contains the correct mixture of aniline and cyclohexane to form a binary fluid when heated above its critical point, about 95 degrees Fahrenheit. The fluid is heated by hand or using a beaker of warm water. Then the vial is placed in the laser beam. When the fluid cools down to its critical point it breaks into cells, becoming cloudy, and scatters the laser beam chaotically. This is very dramatic because it happens very quickly.

    The photographs above show the scattering of the laser beam by the fluid above the critical point (left), at the critical point, when the cells are beginning to form (center), and well below the critical point, when the fluid is a cloudy mixture of the two individual fluids (right)
    I4, I0, FS1

    i4-61i4-61ai4-61b

  • I5-22 FIRE SYRINGE

    I5-22
    Demonstrates heating air by compression

    This demonstration consists of a transparent cylinder with a flared base, and a plunger that can be pushed into it. A small (very small) piece of cotton is pushed into the bottom of the tube using the wire provided, and the plunger is sealed into the tube. The plunger is pushed down sharply, compressing and thereby heating the air within. The temperature rises high enough to ignite the cotton with a flash, which can be readily seen through the plastic tube.
    Engagement Suggestion
    • Consider inviting a volunteer from the audience to try the demonstration. This will require careful supervision, but is safe. Just ensure that the syringe isn't knocked off the table by an overenthusiastic student!
    • This demonstration works best with a very small amount of cotton to ignite, no more than a few millimeters at most. Consider showing the device with different amounts of cotton, and how the results change. Encourage students to discuss reasons for this.
    Background
    This demonstration illustrates that an essentially fixed mass of air will increase in temperature when its volume is reduced, i.e. it is heated when compressed. The fire syringe is a simple piston, and can be used to introduce a discussion of the use of pistons in engines.

    Consider using this demonstration in conjunction with both other thermodynamics demonstrations from section I5, and relating it back to general gas behaviour with demonstrations from section I3.
    I5

  • 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

  • I6-01 GAS PRESSURE - MODEL

    I6-01
    Illustrates the molecular nature of gas pressure
    A vibrator motor is activated causing chaotic motion of a group of ball bearings in a clear plastic container. The upward motion of the ball bearings pushes a black plastic plate upward, indicating the upward force of "air pressure" on the plate. Increasing the speed of the motor by turning up the variac increases the average speed of the balls and pushes the plate up further, modeling a greater pressure.
    I6, PW1

  • I6-34: MOLECULAR MOTION DEMO - TEMPERATURE OF A GAS

    I6-34
    Model gas pressure.
    Two sets of small balls (larger green and smaller blue) are used to model the molecules in the air. The balls are set into motion by vibration of the walls. Increasing the vibration speed of the walls imparts more energy to the balls, simulating higher temperature.

    Using a single set of balls, the distribution of velocities can be observed. Using two sets of balls with different mass, the average velocity of the smaller balls is seen to be greater than that of the larger balls.
    I6, PW1

    i6-34a

  • I6-40: MOLECULAR MOTION DEMO - SOLIDS

    I6-40
    Model the behavior of solids.
    A set of small balls of equal mass is placed in the vibrator in a curved glass dish with the concave side up. The gravitational force caused by the curvature of the dish causes them to form an array, corresponding to a crystal lattice. As the vibrator motion is increased, the molecules do not move about randomly, but rather vibrate about their original positions, representing vibratory motion of atoms in a crystal lattice.

    i6-40ai6-40b

  • I6-41: MOLECULAR MOTION DEMO - LIQUIDS

    I6-41
    Model the behavior of liquids.
    Using the arrangement of balls from the solid (Demonstation I6-40), the vibration speed is further increased. The balls remain in a small clump, with a few "boiling off" but most free to migrate within the tight clump, representing molecular motion within the liquid state. Use of a Variac operating at 140 VAC makes this effect more clear.

    i6-41ai6-41b