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Safety Equipment: Gloves

  • A1-03: DENSITY - VARIOUS BRICKS

    A1-03
    Demonstrate the concept of density
    This demonstration consists of several bricks of approximately the standard "brick" size and shape, made of various materials such as foam, concrete, steel, and lead. Because the sizes are similar and the weights different, the feature creating the difference must be the density, or mass per unit volume. Invite students to make predictions about which will be heavier, then come up to pick them up and test their predictions.
    OS6

  • C3-04: INERTIA - LEAD BRICK AND HAND

    C3-04
    Illustrates inertia of rest

    Place the lead brick gently on your fingers and strike the lead brick sharply with the hammer. The inertia of the lead brick prevents damage to your fingers.

    Engagement Suggestion
    • This is a visually impressive way to get students’ attention at the beginning of a discussion of inertia.
    • This can be used as a volunteer participation demonstration, but please be very careful.
    C3

  • C5-16: HERO'S ENGINE

    C5-16
    Demonstrate action and reaction in a rotational system.

    The boiler is partially filled with water and heated until steam is produced. The steam emerges from right-angle arms on the side of the boiler, causing the boiler to rotate in the direction opposite to that of the emerging steam.

    Danger:Do not tilt burner until it is warm.
    C5, I0

  • C5-17: ROCKET BOTTLE

    C5-17
    Illustrate the rocket principle in a dramatic way
    Pour about 100-200 ml of liquid nitrogen into the bottle and install the stopper. Exhausting nitrogen gas and liquid result in motion of the bottle. An untethered stopper is available for comparison.
    OS6, I0, F2

  • C7-41: DRY ICE PUCK COLLISIONS

    C7-41
    Demonstrate two-dimensional collisions qualitatively.
    Dry ice in the containers vaporizes, ejecting carbon dioxide gas under pressure out through a small hole under the puck. This provides a layer of gas between the puck and the glass surface to create relatively friction-free motion. Use the two pucks to create two-dimensional elastic collisions.

  • I1-16: THERMAL CONTRACTION OF CUPS WITH LN

    I1-16
    Measure coefficients of linear expansion.
    A cup rests on a fixed platform with the rim of the cup under the feeler gauge. Pour liquid nitrogen into the cup to make it contract and read the length contraction (ha! ha!) on the gauge.

  • I1-51: RUBBER AT LN TEMPERATURE

    I1-51
    Demonstrate how a normally elastic material at room temperature becomes rigid at very low temperatures.
    Dip a rubber sample into the liquid nitrogen with the tongs, then place it on a wooden "anvil" and hit it with a hammer to break it. Show the students in the audience how the material's property change with temperature.
    I0, I1

  • I1-52: TUNING FORK AT LIQUID NITROGEN TEMPERATURE

    I1-52
    Demonstrate the change in frequency of a tuning fork at liquid nitrogen temperature.
    Cool down one of the two identical tuning forks in liquid nitrogen. When it is cooled, beats are observed between identical tuning forks, one of which has been cooled.

  • I1-53: LEAD BELL AT LIQUID NITROGEN TEMPERATURE

    I1-53
    Demonstrate the effect of temperature on vibrations in a lead bell.
    The bell can be sounded at room temperature. It is then cooled by placing it in a bath of liquid nitrogen, after which it is sounded at LN temperature. The difference in the tone can be ascribed to the increased crystalline structure when the bell is cooled.

  • I2-07: THERMOPILE WITH DVM

    I2-07
    Observe infrared radiation.
    The output from a commercial thermopile is connected to a digital voltmeter where the voltage is proportional to the temperature observed: the hotter the object the higher the voltage. Use various sources: ice, boiling water, liquid nitrogen, the floor, people, etc. This is only qualitative; the system is not calibrated.
    N1, ME2, I2, PW1

  • I2-09 DEWAR - TRANSPARENT WITH LIQUID NITROGEN

    I2-09
    Demonstrates a dewar
    The dewar contains liquid nitrogen, which can be seen as a clear liquid. Various experiments using liquid nitrogen can also be performed
    I2, I0

  • I2-12: RADIATION FROM COLD OBJECT

    I2-12
    Show radiation from a cold object
    If you put a hot object at the focus of one of the concave parabolic mirrors and a thermal probe at the focus of the other mirror, heat from the hot object will heat up the probe, yielding a temperature rise of the thermometer. (Compare the top and center pictures above.) If you put something very cold at the first focus, the temperature will drop. (Compare the top and bottom pictures above.) This demands a rather different explanation - blackbody radiation emitted by all objects - than the rather simple explanation given in the case of the hot object.

    This experiment demands the proper explanation in terms of blackbody radiation emitted by all objects, not just "hot" objects. The historical struggle of physicists to deal with this is documented in an interesting article by Hasok Chang, Lecturer in Philosophy of Science at University College, University of London, entitled Rumford and the Reflection of Radiant Cold: Historical Reflections and Metaphysical Reflexes, in Physics in Perspective Volume 4 Issue 2 (2002), pp 127-169.

    Note that this experiment uses materials from I5-51 and L3-16. If you want to use those demonstrations in the same class, be sure to discuss logistics with Lecture-Demonstration staff in advance.
    I2, I0, I5, L3

    I2-12A

  • I2-21 THERMAL CONDUCTIVITY IN METALS

    I2-21
    Demonstrates thermal conductivity in various metals
    Heat from a gas burner at the center is conducted along rods of copper, aluminum, and brass. Wax blocks at the ends of the rods melt and drop off the rods due to the conduction of heat, in the following order: copper (3.98 Watts/cm deg C), aluminum (2.37 Watts/cm deg C), and brass (1.23 Watts/cm deg C).
    I2, I0

  • I2-24: THERMAL CONDUCTIVITY IN WATER

    I2-24
    Demonstrate that water is a poor conductor of heat.
    An immersion heater placed at the top of a dewar of water causes the water near the top of the dewar to boil. However, heat is not readily conducted through the water to the bottom, and the bottom remains at a much lower temperature even 15-20 minutes after the water on top begins to boil.

  • I2-27: THERMAL EQUILIBRIUM BETWEEN ALUMINUM AND COPPER

    I2-27
    Show process of thermal equilibrium happening between touching aluminum and copper cylinders.
    Pieces of copper and aluminum are held together by a large C-clamp. Small holes are drilled into the pieces to a allow a digital thermometer probe to be inserted to measure the temperature of each block, showing that the blocks are initially the same temperature, at equilibrium. Remove the thermometer probes and put a flame under one block to create a temperature difference. Remove the flame, reinsert the probes, and watch as the blocks come to thermal equilibrium.
    I2, I0, tools

  • I2-43: CONVECTION - HOT PLATE

    I2-43
    See convection currents.
    The irregular refraction patterns created by convection currents in air heated from below are easily seen when light from a point source (foreground) shines through the air over a hot plate and onto a screen. This phenomenon is often seen when the sun shines brightly onto surfaces like cars and roads, and is responsible for the twinkling of stars.
    I0, LS1

  • I2-45: CONVECTION - HIGH/LOW CANDLES IN CYLINDER

    I2-45
    Brainteaser regarding convection.

    Two candles, one at the level of the table and one raised approximately 30 cm, are lit and then covered by a tube about 50 cm high and 10 cm in diameter. The tube is sealed at the top by a dark plastic cover to prevent air from flowing into the tube as the experiment progresses.

    Engagement Suggestion:
    • Encourage students to predict which candle will go out first, and why.
    • As the demonstration will typically take 2-4 minutes, discuss other related matters and then check in on the demonstration from time to time; ask students if it is behaving as they expected.
    • When both candles have gone out, ask students to discuss what they saw.
    Background:

    As the candles burn, the hot gases composing the products of combustion will be less dense than the cooler original air, and will rise to the top of the tube. The upper candle will therefore be extinguished sooner than the lower one.
    I2

    ii2-45ai2-45bi2-45ci2-45d

     

     

    Two candles, shown in the photograph at the left below, are lit and then covered by a plastic tube (sealed at the top), as seen in the photograph at the right below. In the apparatus as pictured the tube is about 50 cm tall and 10 cm in diameter, and the upper candle is about 30 cm from the bottom.

     

    i2 45 i2 45a

     

    After some period of time, as the oxygen in the tube is consumed by the candle flames, the candles will both cease to burn. The question involves the order in which the candles will go out.

    Which of the following statements is true?

     

     

    • (a) The top candle will go out first, then the bottom candle.
    • (b) The bottom candle will go out first, then the top candle.
    • (c) Both candles will go out at the same time.

     

  • I3-31: IDEAL GAS LAW - VOLUME OF ONE MOLE

    I3-31
    Demonstrate that one mole of gas occupies 22.4 liters at STP.
    Pour liquid nitrogen into the small beaker and let it boil down to about 35 ml. The density of liquid nitrogen is 0.808 g/ml, so one mole has a mass of 28 grams and occupies about 35 ml. Install the neck of the balloon over the beaker, and allow the liquid nitrogen to evaporate, filling the balloon. Determine the average circumference of the balloon and from that calculate the diameter. The approximate volume of one mole of nitrogen gas at atmospheric pressure is then V= 4 pi r3/3, which can be readily calculated. This determination is good to better than ten percent.
    I3, I0

  • I3-32: ISOBARIC EXPANSION OF AIR

    I3-32
    Demonstrate expansion of air without change in pressure.
    Air is isolated in the can by a plastic bag sealed over the mouth. If the can is heated by the hot plate the air will expand to fill the plastic bag. If the can is removed from the hot plate and the fan blows cool air over the can the plastic bag will again become evacuated.

  • 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