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Thermal Properties of Matter

  • I1-62: DUST EXPLOSION MODEL

    I1-62
    Show why small particles of flammable material can create a dust explosion when ignited.
    The large cube, red on the outside, is broken into 27 smaller cubes, increasing the surface area but not the volume. Note that only a small fraction of the total area of the small cubes is red! The ability of a material to burn or even explode (burn very rapidly) increases with its surface area. This illustrates why clouds of small particles, such as wheat or sawdust, may produce a "dust explosion."
    I1

    i1-62a

  • I1-63: HYDROGEN EXPLOSION

    I1-63
    Produce a hydrogen explosion

    A balloon filled with hydrogen is tethered about six feet above head level. The burning match on a stick is positioned under the balloon, creating the hydrogen explosion.
    Engagement Suggestion
    • One option for presenting this would be to compare the behaviour of two different balloons, hydrogen and helium. You can tell students what is in each balloon and have them make a prediction about what each will do, or show the demonstration first and then have students analyze why the results were different.
    I1, I0, FS1

    I1-63B

  • I1-64: BURNING CANDLE - COMBUSTION PROCESS

    I1-63
    Demonstrate features of the burning process and to debunk myths about this supposedly well-known demonstration.

    A common pre-college experiment is to burn a candle inside of a bottle which has been turned upside down over a container of water. The water supposedly rises about one-fifth of the way up the bottle, indicating that the oxygen, about one-fifth of the air in the atmosphere, has been "used up" in the combustion process.

    The candle in our experiment is placed inside the sealed tube containing air above a colored water bath, and is then ignited by a hot wire (center photograph). The water level goes down initially, then returns to its original level just after the candle goes out. There is virtually NO CHANGE in the water level from before to after the experiment is performed (photograph at right).

    This is the CORRECT WAY to do this experiment. Two experimental errors are often made when performing this experiment: (1) if the candle is lit before the bottle is placed over it, the air is initially hot, and will pull the water up the bottle as it cools, and (2) when the bottle is placed over the candle, the hot air from the candle flame expands, and some of it might escape out of the bottom opening of the bottle. Analysis of the chemistry of this experiment shows that the final products of combustion are actually more voluminous than the initial air, but other things happen to yield no net difference in the water level.
    I1

    i1-64a

    i1-64b

  • I1-71: SHAPE-MEMORY ALLOY - THERMOBILE

    I1-71
    Ilustrate shape-memory alloy.
    A loop of 0.012 inch NITINOL wire is wound around an upper plastic pulley and a lower brass pulley. When the lower brass pulley is immersed about half way into water at 60 degrees celcius, the wire rotates, acting as a heat engine.

    i1-71a

  • I1-72: SHAPE-MEMORY ALLOY - ICEMOBILE

    I1-72
    Illustrate shape-memory alloy.

    A thin NITINOL wire loop is connected around two pulleys. The lower pulley is placed half way into the water at 35-40 degrees celcius and an ice cube gently touched to the wire. If the wire is gently spun downward through the ice cube into the water bath, it will continue to spin, cutting the ice cube in two.

    Alternatively, a glob of crushed ice placed around the wire as it enters the box will cause the wire to circulate as described above, as shown in the photograph.

  • I1-73: SHAPE-MEMORY ALLOY - COOL CRAFT

    I1-73
    Illustrate shape-memory alloy.
    A few cubes of ice or a bit of crushed ice are placed into the boat and the boat is placed in a water bath at about 27-38 degrees celcius. If the red wheel is spun forward the NITINOL wire will function as a heat engine and propel the boat.

  • I1-74: SHAPE-MEMORY ALLOY - CLOVER

    I1-74
    Illustrate shape-memory alloy.
    Gently bend the clover-shaped NITINOL wire into a funny shape (top of photograph above) and heat it brieifly with a match to return it to its original shape. For large groups place the clover in a glass container on an overhead projector platform before heating with a heat gun.

  • 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

  • I2-21 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

  • I2-22 THERMODYNAMICS BY TOUCH

    I2-22
    Demonstrates that touching a material tells something about its conductivity, not necessarily its temperature
    Various materials, all at room temperature, are arranged on a cart, and students are invited to touch them. The materials in order of increasing conductivity, are: styrofoam, wood, plastic, slate, steel, aluminum, and copper.
    I2

  • 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.

  • I2-26: LEIDENFROST PHENOMENON

    I2-26
    Demonstrate the Leidenfrost effect.
    Turn on the hot plate to high for about two minutes to pre-heat the aluminum sheet/skillet. Then squirt a few large drops of water (with green food coloring to make it visible) onto the aluminum skillet. The water forms drops which skitter around on the hot plate for an unexpectedly long duration, because of an insulating layer of water vapor (steam). Big drops can be created which will persist for a minute or longer, while executing interesting oscillations. This is known as the Leidenfrost phenomenon.

    i2-26a

  • 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

  • I2-28: WATER BALLOON AND CANDLE

    I2-28
    To demonstrate the transfer of heat by water
    A balloon filled with water is held above a candle flame. Contrary to most students' expectations, the balloon does not burst. The water in the balloon conducts heat away from the rubber before it can melt.
    I0

  • I2-29: Thermal Conductivity - Metal Bars and Liquid Crystals

    I2-29
    To show the different rates of heat conduction in several metals
    This demonstration consists of a series of bars of different metals, with temperature-sensitive liquid crystal strips attached to each. When the tips of the bars (and only the tips) are lowered into a beaker of hot water, the liquid crystal strips will change colour at different rats, showing the different rates of heat conduction of the different metals.

    Note: Use water no hotter than 90C. Do not expose to open flame, and do not apply water or heat to the liquid crystal strips, and keep them out of direct sunlight.
    I2

  • I2-42: FALLING CANDLE

    I2-42
    Demonstrate how a flame burns in the absence of normal convection.
    A candle, attached to the lid of a one-gallon jug, is lit and the lid screwed onto the upside-down jug. Throw the upside-down jug into the air and catch it or hold the upside-down jug high and drop it and catch it as it falls. While it is falling, the system inside the jar is in a weightless environment, so convection currents cease. In normal burning, the hot air rises by convection, allowing cooler air containing more oxygen to continuously feed the fire. Without these convection currents the candle should immediately go out, BUT IT DOES NOT.
    I2

    A candle mounted on the lid of a gallon jug is lit, and the lid quickly affixed to the jug. In this configuration the candle will remain lit for over one minute before the oxygen in the jug is sufficiently used up by the combustion process and the flame is extinguished.

    Now suppose that the candle flame is lit and the lid again quickly affixed to the jug. However, the bottle is now dropped about six feet starting from the orientation shown in the photograph below.

    i2 42

    What will happen? In particular, by the time the jug falls six feet the candle flame will:

    • (a) burn more brightly.(b) remain at about the same brightness.
    • (c) burn less brightly.
    • (d) go out.

     

  • I3-03: GALILEO'S THERMOSCOPE

    I3-03
    Measure very small pressure changes.
    Without touching the can, disconnect and reconnect the tubing from the Magnahelic gauge in order to set the gauge pressure to zero. Warming the can by placing your hand on it raises the pressure in the can about half of the full scale. Also try warming the can by breathing on it.
    I3

    i3-03a

  • I3-04: GALILEAN THERMOMETER

    I3-04
    Illustrate a very heat-sensitive device.
    This air thermoscope consists of a flask sealed with a stopper with a 4 mm diameter 50 cm long glass tube inserted into the (colored) water bath in the bottom of the flask such that the water level in the tube is at the level of the water in the flask. The water level in the tube rises when the flask is warmed by snuggling it in your hands.
    I3

    i3-04a

  • 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