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Table of ContentsThermal Expansion of Air (Galileo's Thermometer) -- air expansion in a glass bulb causes liquid level in a vertical tube below the bulb to drop - qualitative only.
Thermal Expansion of Water -- a 1 liter flask filled with colored water has a long glass tube protruding up from the neck. Run a flame quickly under the flask, and thermal expansion forces water up the tube.
Gas Pressure -- A hollow metal sphere is attached via tubing to a pressure gauge on the OH. The sphere is immersed in water baths of various temperatures (boiling, room temperature, and ice water) and the corresponding pressure is noted. The data can be extrapolated to absolute zero if desired. See also Constant Volume Gas Thermometer, below.
Constant Volume Gas (Pressure Thermometer) -- constant volume is maintained by adjusting a water column, and pressure is read from the height of water in the other leg of the tube. Qualitative only, and only usable for small changes in pressure
Electrical Resistance -- two demos are available: (1) Heated Wire - a resistance wire in series with a small lamp and an ammeter is heated by a gas flame. The resistance of the wire increases with rising temperature, causing the current to decrease and the lamp to dim; and (2) Coil in Liquid Nitrogen - a bulb in series with a resistance coil barely glows at room temperature, but dipping the coil in liquid nitrogen lowers its resistance and the bulb lights brightly.
Thermistor -- resistance of this electronic component decreases dramatically with increasing temperature.
Liquid Crystal Sheets -- large sheets of temperature-sensitive liquid crystals change color with changing temperature.
Liquid -- mercury or alcohol.
Bimetallic Coil -- large or small models.
Liquid Crystal Thermometer -- aquarium type thermometer strip indicates temperatures from 66 °F to 84 °F by color changes.
Film Loops:
- Temperature, Energy, and Thermal Equilibrium
Specific Heat (Rods and Wax) -- cylinders of lead, brass, and aluminum are heated in boiling water, then lifted onto a block of paraffin. The plugs melt through the wax with speeds approximately proportional to their heat capacities.
Specific Heat (Quantitative) -- three equal masses of metal shot (aluminum, steel, and lead) are placed in pop cans and heated in boiling water until they are all at 100 oC. They are then each dumped into equal masses of water and stirred, then the final temperature of each is read with a large display thermometer. Reasonable (10%) figures for the heat capacities of the metals can be obtained from the data. The results will always be slightly on the low side due to heat losses during transfer, but are good to 10-15%.
Calorimeter -- Show & Tell version of a double-walled aluminum calorimeter with hole on top for thermometer, used for heat of fusion of water, etc.
Water Balloon Heat Capacity -- a lit match may be held directly beneath a water balloon without burning through the balloon, due to the high heat capacity of the water. In contrast, an air balloon explodes immediately on contact with the flame.
Air Expansion -- Galaileo's classic air thermometer, in which air expansion in a glass bulb forces liquid down a vertical tube.
Helium Balloon in Liquid Nitrogen -- a helium balloon dipped in LN2 will shrink to half its size, expand again as it warms.
Ball and Ring -- a metal ball and ring on handles are constructed so that the ball will just pass through the ring at room temperature. The ball is heated and will not pass through the ring. The ball and ring are both heated and the ball now passes through the heated ring.
Ball and Hole -- a ball which is too large to pass through a hole in a square metal plate will pass easily through the hole after the plate has been heated in a flame. Many students expect the hole to shrink upon heating, but it actually expands along with the rest of the plate.
Bimetallic Strip -- two dissimilar metal strips bonded together and fastened to a handle. When heated, the strip bends because of the different expansion rates of the metals.
Bimetallic Coil -- same as the bimetallic strip in concept, but helical in form. The coil is heated and moves a large indicator arrow as it expands.
Heated Wire -- a thin wire supported at both ends is electrically heated and the wire sags in the middle.
Expansion of Metals -- metal tubing of different materials are heated to equal temperatures by passing steam through them. As they expand they roll over a small metal rod, turning a pointer to indicate the amount of expansion.
Thermostat Model -- working model of a thermostat with a lamp heater and a bimetallic strip.
Negative Expansion Coefficient of Water -- a 2 liter flask of colored water with a glass tube inserted through the stopper is kept in a bath of ice water until the temperature of the water in the flask has fallen to 0 °C. The water level in the vertical tube is noted, and the flask and tube are removed from the ice bath. As the temperature of the flask water rises above 0 °C, the water level in the tube drops until the water has warmed to about 4 °C, the temperature of maximum density, then begins to rise. Demonstrates why ice floats, and always forms at the top surface of the water.
Density of 4°C Water -- a mixture of ice and water in a beaker is placed on a styrofoam insulation pad. After coming to equilibrium, a large display thermometer can be used to show that the water up around the ice is at 0 °C, while the denser water at the bottom is at 4 °C.
Thermal Conductivity -- five rods of different composition are attached to a steam chamber to provide equal temperatures at the bases of the rods. The rods are covered with wax, which melts and peels off as the rods heat up. Relative rates of heat conduction can be deduced from the rates at which the wax melts on each rod. The five materials in order of decreasing conductivity are: copper, aluminum, brass, steel, and glass.
Convection Currents (Projection) -- convection currents from a hot wire in a small water cell are projected onto a screen using a simple Schlieren optics system.
Convection (D-tube) -- a large glass tube in the shape of a “D” is filled with water and heated by a burner near one bottom corner. The resulting circulating convection current is shown by adding drops of dye to the water.
Convection with Overhead -- a bunsen flame held between the overhead and screen clearly shows convection currents rising from the flame.
Infrared in Spectrum w/Thermopile (Planck Curve) -- light from a hot carbon arc isspread into a spectrum, then various portions of the spectrum are scanned with a thermopile. It is shown that the greatest amount of energy is in the infrared portion of the spectrum where no visible light exists, then tapers off into the visible and disappears in the ultraviolet. A new thermopile that drives a vertical LED display can be used to graph out the spectral emission curve for the carbon arc.
Radiation Spectrum of a Hot Object -- light from a slide projector powered by a Variac is spread into a spectrum. With the Variac at a low setting the projector bulb is red-hot and the spectrum consists of red light only. Turn the Variac up slowly, and as the temperature of the bulb increases the spectrum comes to include orange, yellow, green, and (at white heat) blue light.
Bichsel Boxes -- two 3x5 index card boxes each with a small hole in the lid; one is painted black inside and the other white. Hold the boxes up to the students with the holes facing them and they appear almost identical. Open the lids and the difference is obvious. Useful in discussing blackbody cavity radiation.
Blackbody Radiator -- a small metal cube has a narrow hole drilled in the side. As viewed with a video camera, the hole appears darker than the surrounding metal. If the cube is heated with a blowtorch to a high enough temperature, the hole will glow brighter than the surrounding metal.
Insulation -- four dewar flasks (thermos bottles) are filled with boiling water and a thermometer and cork are placed in each mouth. Each flask has a different degree of insulation, and these are (from worst to best): not silvered and no vaccum between the walls, silvered with no vacuum, not silvered with a vacuum, and silvered with a vacuum. Water is left cooling until the end of the period, then temperature of each flask is read on a thermometer and relative rates of heat transfer are inferred from the different temperatures.
Leslie Cube -- a brass cube filled with hot water has four different faces: one is plain brass, one painted white, one painted glossy black, and one painted flat black. A thermocouple connected to a projection galvanometer is positioned near the Leslie cube and the cube is rotated on its base so that each face passes in front of the thermocouple. A different rate of radiation is seen from each face.
Radiation (Hot Body) -- two parabolic reflectors are aligned facing each other on the lecture table, with a thermopile at the focal point of one of the reflectors and a heated sphere at the other. A projection galvanometer's deflection shows the transmission of heat by radiation.
Radiation (Cold Body) -- sphere dipped in liquid nitrogen can replace the hot body in the above demo and will deflect the galvanometer in the opposite direction.
Calorimeter -- Show & Tell version of a double-walled aluminum calorimeter with hole on top for thermometer, used for heat of fusion of water, etc.
Heat by Friction -- wooden dowel held in electric drill chuck is ground against a large flat piece of wood. The friction between the two produces heat, smoke, etc.
Cork Popper -- a motorized rotating hollow shaft holds a thimblefull of water and is sealed with a stopper. Wooden arms are squeezed together on either side of the rotating shaft, and the heat generated by friction boils the water and pops the cork.
Heron's Engine -- working model of the first primitive steam engine. A glass globe containing a small amount of water is heated with a flame. The steam produced comes out through two arms and spins the globe.
Stirling Engine -- working Stirling cycle engine powered by a gas flame. Works well but the pistons etc. can’t be seen.
New Stirling Engine -- a new model Stirling engine has glass cylinders so the power and displacement pistons can be viewed (a video camera helps, and an animation of the process is available on The Video Encyclopedia of Physics Demonstrations).
Newer Stirling Engine -- yet another in our expanding line of Stirling engines. This one runs off any sort of a temperature differential, and doesn’t need much of a DT. It will run on a cup of hot water, or (in reverse) on a block of ice. As the DT decreases with time, the engine slows down. Doesn’t need a flame, so it’s useful to show that hot and cold reservoirs are all it takes to produce work from heat energy.
Newest Stirling Engine -- our newest Striling engine is so well machined and balanced that it can run off the heat from your hand. Quite impressive.
Cutaway Steam Engine -- cutaway model of a steam engine shows the steam chamber, piston, valves, etc.
Air Piston Car -- toy car uses the energy stored in a syringe of compressed air to impart motion to its wheels and travel across the table.
He and CO2 Balloons in Liquid Nitrogen -- two ballons are filled with helium and carbon dioxide, respectively, then drenched with liquid nitrogen. The helium shrinks in volume but stays gaseous, while the CO2 changes phase and collapses its balloon entirely. The CO2 balloon can then be cut open to show solid CO2 (project on OH).
Liquid Nitrogen in Balloon -- a small amount of liquid nitrogen is poured into a balloon and allowed to evaporate and expand.
Sublimation -- CO2 is solidified by dipping a balloonful in a container of liquid nitrogen. The balloon is cut open to show the solid CO2, which sublimates directly to the gaseous state.
Triple Point of Water -- air pressure is lowered almost to vacuum over a small sample of water, which begins to boil. Evaporation in vacuum lowers temperature of the water until it reaches triple point at .01 °C. Water then boils and freezes almost simultaneously - displayed on the overhead projector or with a video camera (preferred).
Boil Water Under Reduced Pressure -- a special long-necked spherical flask with a concave depression in its bottom is filled with water and boiled to drive out the air. The flask is then capped with a cork and thermometer (which shows the water is boiling at 100 °C), turned upside down, and cooled by filling the hollow with ice. The resulting pressure reduction causes the water to boil at a reduced temperature (80-90 °C or lower).
Cloud Flask -- a flask containing a small amount of water has a large rubber bulb attaced to the side. If the bulb is squeezed and released, a cloud will form in the flask, but only if a small amount of smoke is added first to act as condensation centers.
Negative Expansion Coefficient of Water -- a 2 liter flask of colored water with a glass tube inserted through the stopper is kept in a bath of ice water until the temperature of the water in the flask has fallen to 0 °C. The water level in the vertical tube is noted, and the flask and tube are removed from the ice bath. As the temperature of the flask water rises above 0 °C, the water level in the tube drops until the water has warmed to about 4 °C, the temperature of maximum density, then begins to rise. Demonstrates why ice floats, and always forms at the top surface of the water.
CO2 Critical Point Tube -- liquid CO2 in a glass tube at high pressure is close enough to the critical point that warm air from a blow dryer will complete the transition. The tube is displayed on the OH projector and the meniscus is seen, but when the tube is heated the meniscus slowly fades and disappears as the liquid CO2 goes through a gradual transition to a high-pressure gas. A turbulent mixture of liquid and gas with equal densities is seen above and below the miniscus point.
Critical Opalescence -- a mixture of triethylamine and water in a tube is hand warmed and passes through the liquid/gas critical point. The liquid is clear at first, then clouds up as the critical point is reached; a sparkly meniscus forms at the phase interface.
Drinking Bird -- commercial novelty. Dip the bird's beak into a beaker of water, then let it go. Evaporation of the water from the wet beak cools the beak, lowering the vapor pressure of the liquid inside and drawing it up into the head. That overbalances the bird and he tips into the water for a “drink”. In that position, the liquid inside flows back into the lower bulb, which rights the bird and starts the cycle over.
PVT Surface Model (Carbon Dioxide) -- a three dimensional model showing various PVT states of carbon dioxide.
PVT Surface Model (Water) -- a three dimensional model showing various PVT states of water.
Hand Boiler -- convoluted glass tube contains a small amount of a volatile liquid. Heat from your hand will boil the liquid and the vapor pressure will force it to flow to the opposite end of the tube.
Exothermic Reaction -- a small pouch contains a solution of water and a salt that dissolves endothermically (absorbs heat as it dissolves). When a small snapper inside the pouch is popped, the salt comes out of solution, releasing the heat it had absorbed while dissolving. The pouch can be rechearged by placing it in boiling water until the salt dissolves. This is a commercial item used by campers for supplemental warmth. Please give plenty of notice for this demonstration.
Regelation -- a block of ice is supported at ends and a thin wire with weights attached is hung over the top. Pressure from the wire raises the melting temperature of the ice , and the wire will pass through the block without cutting it in two (the ice refreezes behind the wire) within 15 to 30 minutes. Ice skating and the making of snowballs are two examples of regelation at work.
Molecular Motion Demonstrator -- a small variable speed motor shakes a four-sided frame mounted over a glass plate on the overhead projector. Various sized plastic and metal balls placed in the frame bounce randomly about, simulating molecular motion. Concepts which may be demonstrated include temperature, equipartition of energy, diffusion, and Brownian motion.
PVT Surface for an Ideal Gas -- a smooth surface that shows the three-deminsional graph of the relationships between pressure, volume, and temperature for an ideal gas.
PVT Surface Model (Carbon Dioxide) -- a three dimensional model showing the relationships between P, V, and T for the different phases of carbon dioxide.
PVT Surface Model (Water) -- a three dimensional model showing the relationships between P, V, and T for the various phases of water.
Boyle's Law -- A syringe is connected to a dial pressure gauge on the overhead projector. A decrease in volume of the syringe causes an inversely proportional increase in the pressure. An increase in the volume results in a decrease in the pressure.
Temperature vs Pressure (Charles' Law) -- A hollow metal sphere is attached via tubing to the pressure gauge used above. Pressure at room temperature is noted, then the bulb is immersed in ice water and boiling water to obtain pressure readings at those temperatures. The data can be extrapolated to absolute zero with surprising accuracy.
Temperature Change with Compression -- a small plastic syringe contains a small thermocouple probe in the tip that connect to a large display thermometer. If the syringe is compressed rapidly, a temperature rise is seen on the thermometer. Pulling the plunger up rapidly lowers the temperature of the air inside.
Fire Syringe -- A thick glass tube with a plunger has a small amount of match-head shavings in the bottom. If the plunger is rapidly pushed in, the heat of compression ignites the match shavings with a bright flare.
Cloud Flask -- a flask containing a small amount of water has a large rubber bulb attaced to the side. If the bulb is squeezed and released, a cloud will form in the flask, but only if a small amount of smoke is added first to act as condensation centers.
Diffusion -- an upside-down porous clay bottle with tubing leading out of the bottom and into a test tube of water is placed under an inverted beaker. Natural gas or helium is introduced into the beaker, and the osmotic pressure between the two gases forces air out of the bottle and down the tubing, so that bubbles are seen coming from the end of the tubing. After the cup fills entirely with natural gas, a new equilibrium is reached and the bubbles stop.
Brownian Motion -- a small chamber is filled with smoke and observed with a Brownian video camera and projection TV. Brownian motion of the smoke particles is observed.
Gaussian Distribution -- hundreds of tiny balls roll down through a gap and strike an array of pins below, bouncing between them and eventually landing in one of a number of slots below. The center slot will contain the greatest number of balls, and the number of balls in the outer slots will approximately follow a Gaussian distribution. The device sits on the overhead projector for class viewing.
Entropy Pennies -- a tray is filled with pennies painted green on the tails and red on the heads. If the tray is shaken the pennies begin to flip at a rate dependent on the magnitude of the shaking. Eventually an equilibrium is reached, with approximately equal numbers of reds and greens. Furhter shaking will not, of course, return them to their original state. If only a few pennies are used, they will occasional return to their original state, showing the dependence upon the number of “particles” in the system.
Film Loops:
- Pressure, Volume, and Boyle's Law
- Avogadro's Principle
- Heating, Cooling, and Charles' Law
- Ideal Gas Law
- Brownian Motion and Random Walk
- Deviations From Ideal Gas
- Dalton's Law (Partial Pressures)
- Graham's Law (Diffusion)
- Maxwell-Boltzmann Distribution
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