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  • 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

  • I4-14: 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

  • I4-16: 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

  • I5-03: MECHANICAL EQUIVALENT OF HEAT - JOULE'S METHOD

    I5-03
    Determine the mechanical equivalent of heat.
    Turning the handle with weights hanging from a cord wrapped around the copper cylinder requires a calculable amount of mechanical energy. This energy is converted into heat in the copper cylinder and the water bath, raising their temperature. The constant of proportional, which is the mechanical equivalent of heat, can be calculated using these two measurements. The device counts turns, so you can continue to lecture while cranking, typically 100-150 turns. The result is generally good to better than ten percent. (Note that when you turn the handle the heavy weight should be lifted off the floor, so the net frictional force causing the heating of the cylinder is the difference between the weights on the two ends of the cord.)
    I5, I0

    i5-03a

  • I6-11: BROWNIAN MOTION WITH TV

    I6-11
    Demonstrate Brownian motion.
    A smoke cell is mounted on a tube connected to a TV camera. On the end of the tube inside the cell is a microscope lens which casts an image of smoke particles in the cell onto the videcon of the TV camera. The focal plane of the microscope/TV system is illuminated by a laser to avoid creation of convection currents by heating with a more powerful light source. A twisted lab tissue is burned and blown out, and while it is smoking the rubber bulb on top of the smoke cell is used to snort smoke into the cell through a tube in the bottom of the cell. After a few seconds convection ceases and Brownian motion is clearly visible on the TV monitor to large groups. The photographs above show the entire system (left), the laser beam entering the smoke cell which is in turn mounted on the video camera (center), and the output of the video camera sent directly to the video frame grabber used to capture the images (right). Clicking on the link below will play a 30 second MPEG movie of the particles in motion.

    i6-11i6-11ai6-11b

  • I6-12: BROWNIAN MOTION - SMALL VERSION

    I6-12
    View Brownian motion individually.
    This is a standard version an illustration of Brownian motion with a microscope and a smoke cell for individual viewing.

  • I6-25: DIFFUSION - DISTRIBUTION OF PING PONG BALLS

    I6-25
    Demonstrate on a macroscopic scale using ping pong balls how random molecular motion causes substances to diffuse.

    This model consists of a wooden frame with clear plastic covers, about one ping pong ball in width, ten bins at the top and bottom for setting up initial and analyzing final distributions, with several rows of pegs in between. When the horizontal plastic baffle holding the balls at the top is pulled away, balls will drop through the peg array, become randomly scattered, and drop into bins at the bottom.
    Engagement Suggestions
    • Put four orange balls into bin 5 and four white balls into each of bins 3, 4, 6, and 7. Challenge students to predict whether they will keep this same arrangement as they fall. (When the balls reach the bottom, the four orange balls will have become distributed into the white balls.)
    Background
    This shows on a larger scale how random molecular motion causes substances to diffuse. The array of fallen balls will approximate a probability curve; this is an opportunity to introduce statistical concepts in a physical, measurable manner.

    i6-25a

  • I6-31: MOLECULAR MOTION DEMO - BROWNIAN MOTION

    I6-31
    Model Brownian motion.
    A set of small balls models the air. The balls are set into motion by vibration of the walls. A large mass models a smoke particle which is moved about randomly by collisions with the smaller air molecules. The device must be tilted so that the balls will not stop moving.

    i6-31a

  • I6-32: MOLECULAR MOTION DEMO - RANDOM MOTION IN GASES

    I6-32
    Model random molecular motion.
    A set of small balls of the same mass models the air. Random motion of any ball can be observed.

    i6-32a

  • I6-33: MOLECULAR MOTION DEMO - GAS PRESSURE

    I6-33
    Model gas pressure.
    A set of about 20 steel balls models the air. A bar is positioned in the center of the device so that it will be continuously struck by the moving balls. The balls are set into motion by vibration of the walls with the device tilted. Collisions of the balls with the bar push the bar upward to model the force of a gas on a surface.
    I6, PW1

    i6-33a

  • 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

  • I6-35: MOLECULAR MOTION DEMO - DIFFUSION

    I6-35
    Model gas diffusion.
    Balls with two different masses are placed into the demonstrator, one type on each side of a barrier. A diffusion barrier with a small slot is positioned in the center of the device, and the balls are set into motion by vibration of the walls. The balls will mix, representing diffusion. Differences between smaller and larger balls can be observed, and fluctuations can be discussed.

    i6-35a

  • I6-36: MOLECULAR MOTION DEMO - AVOGADRO'S HYPOTHESIS

    I6-36
    Help justify Avogadro's hypothesis using a model.
    A set of small balls of varying mass models the air. The balls are set into motion by vibration of the walls. Using two sets of six balls with differing mass, start the device in motion. Both sets of balls move around and occupy the entire space. The small balls move faster than the large balls, so they "occupy" the same amount of space overall.

    i6-36a

  • I6-37: MOLECULAR MOTION DEMO - VAN DER WALLS FORCES

    I6-37
    Introduce the concept of attractive force between molecules.
    A set of 9/32" steel balls models the air. The balls are set into motion by vibration of the walls with the device tilted. A weak magnet is placed at one end of the volume. If the velocity of the steel ball molecules is small enough some of the balls will stick to the magnet and to each other, representing condensation.

    i6-37a

  • I6-38: MOLECULAR MOTION DEMO - BOYLE'S LAW

    I6-38
    Model Boyle's law.
    A set of small balls of equal mass models the air. The balls are set into motion by vibration of the walls with the device level. A bar is positioned in the device to divide the volume into two parts, with all of the balls on one side. A rough observation of the rate at which balls hit the wall is then made. The bar is removed, keeping the motion the same. Note that fewer balls hit the same section of wall in the same time, indicating that when the volume increased the pressure decreased.

    i6-38bi6-38a

  • I6-39: MOLECULAR MOTION DEMO - CHARLES' LAW

    I6-39
    Model Charles' law.
    A set of about 20 small steel balls of equal mass models the air. The balls are set into motion by vibration of the walls with the device tilted. A moveable bar positioned in the device is pushed upward by collisions with the balls. As the vibration rate of the walls is raised, raising the temperature and thus increasing the average molecular speed, the bar is pushed further upward, representing increased volume at a constant pressure (the weight of the bar). Use of a 140 Volt Variac extends the temperature range upward to make the trend more clear.
    I6, PW1

    i6-39a

  • I7-09: Spontaneous Ordering - Crystal Formation Models

    I7-09
    Demonstrates the formation of crystal patterns from disordered objects

    A pair of wooden frames can hold a collection of hexagonal objects. When shaken, the objects gradually form into a hexagonal grid, conforming the the container.

    One of the frames has a few additional hexagons fixed to the base; try comparing the time/work required to form a lattice with or without these seeding points.

    Donated by Dr. Stephen Parks.
    I7

  • J1-02: TRIBOELECTRICITY - WATER JET IN AIR

    J1-02
    Illustrate triboelectricity.
    A water jet falls from a reservoir through a small opening and falls into a receptacle can which is electrically connected to an electroscope. The source reservoir is ungrounded and can be shown to be electrically neutral at the beginning of the experiment. The water stream breaks up as it falls, charging the the water droplets falling into the pan, which can be seen from the electroscope. Charging materials may be used to ascertain the sign of the charge on the electroscope, if desired.

  • J2-01: WIMSHURST MACHINE

    J2-01
    Generate high electrostatic potentials.
    Cranking the handle rotates the two plates in opposite directions, generating a large electrostatic potential. The Leyden jars can be charged to increase the intensity of the spark between the two balls on the arms mounted above the Leyden jars. This machine can also be used for other demonstrations requiring high potentials. This gizmo may go up as high as 500,000 volts.
    J2a

  • J4-11: POLAR AND NONPOLAR LIQUIDS

    J4-11
    Demonstrate that non-uniform electric fields produce a force on polar molecules.
    An electrophorus is used to charge an aluminum plate. A stream of carbon tetrachloride (CCl4), a non-polar molecule, is sprayed in front of the charged plate; the stream of carbon tetrachloride is unaffected by the electric field of the plate. A stream of water (H2O) sprayed in front of the charged aluminum plate deflects strongly, indicating that the centroids of the positive and the negative charges are not the same. The non-uniform electric field rotates the molecules and exerts a force on the dipole electric dipole of a non-polar molecule. Models of carbon tetrachloride and water are available to illustrate the polar nature of certain molecules.

    SAFETY NOTE: If you are hesitant to squirt around a volatile, carcinogenic liquid, a non-toxic alternative is light white paraffin oil, a squirt bottle of which is also provided.