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Metals in Acid

Curls of zinc and magnesium are dropped into 2M hydrochloric acid, and bubbles observer'd.

A 600ml beaker, clean and clear, is at the focal point of a camera projecting the image of 500 ml of 2M hydrochloric acid.

A curl of magnesium bubbles wildly, skittering across the surface of the acid.

A curl of zinc sinks to the bottom, and bubbles form at a steady rate.

Precipitation of Lead Iodide

Potassium iodide solution is added to lead nitrate solution, and bright yellow lead iodide precipitates.

Potassium iodide solution is 0.1 M and lead nitrate solution is 0.01M.

The lead nitrate solution is about 350 ml in a 600ml beaker, and the KI sol'n is 200 ml in a 400ml beaker. Pour the potassium iodide sol'n into the lead nitrate.

Glasses and gloves. The finished demonstration is stirred and the precipitate and solution goes in the hazardous waste bucket.

Conductivity of Solutions

A light bulb is lit when the conductivity probe is immersed in an ionic solution.

The solutions are all in labeled 250ml beakers. All are about 150 ml of 0.1M sol'n. In order, the solutions are: tap water, distilled water, sodium chloride, sucrose, acetic acid, hydrochloric acid, sodium hydroxide, ethanol, and barium sulfate. (See video: http://youtu.be/4WillWjxRWw?hd=1)

The simple conductivity tester is on the bench, for the instructor to plug in. An 800ml beaker with 400 ml of distilled water is provided as...

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Weighing Moles

Several samples are weighed on the balance; each is a mole.

The electronic scales are set up in front of the video camera. In a secondary container on the scale platform is a cube of lead weighing 208 g., 18 g of water in a bottle with an empty bottle for tare, and 200.6 g of mercury in a bottle with an empty bottle for tare.

Precipitation of Silver Chloride

Sodium chloride solution is added to silver nitrate solution and a white precipitate of silver chloride is instantly formed.

The silver nitrate solution is around 0.1M, and the sodium chloride solution around 0.5M. Pour the sodium chloride sol'n into the silver nitrate to avoid leaving traces of silver nitrate in the empty beaker.

Wear safety glasses and gloves to prepare and perform this demonstration.

Greenhouse Bottles

Simulation of the greenhouse effect with silvered and unsilvered glass bottles.

What it shows:

Heat energy readily escapes from a clear glass flask, but is trapped inside a silvered flask which rapidly heats up.

How it works:

Two 2L flat bottom Florence flasks, one clear and one silvered (see reference), have identical 10Ω, 25W resistors placed inside them connected in series to a DC supply 1 These resistors act as good sources of infrared radiation. The clear flask readily transmits the IR, but the silvered...

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Earth's Magnetic Field

OHP representation of lines of force using bar magnet and iron filings.

What it shows:

The magnetic field lines of the Earth can be represented by the field lines of a bar magnet.

How it works:

The Earth's magnetic field is basically a magnetic dipole. It can therefore be represented to first approximation by the field of a bar magnet. The shape of the field lines can be highlighted by the sprinkling of iron filings, or by the use of plotting compasses. The latter method has the advantage of showing the variation of dip...

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Rock Samples

Selection of igneous, sedimentary and metamorphic rocks.

What it shows:

A selection of rocks and minerals available for lecture demonstrations

How it works:

The following samples are available for show-and-tell in lecture. The samples vary in size, and only those marked with a 4 are big enough to be seen.

1. A selection of elements in their natural (unrefined) states:
native copper Cu 4
diamond C iso
gold Au
realgar (silver ore) 4
graphite C hex 4
Silver...

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Superconductivity

What it shows:

A superconducting material in the presence of a magnetic field excludes that field from its interior. This is shown by levitating a magnet above a high temperature superconductor.

How it works:

We have a 25mm disc of ceramic yttrium barium copper oxide YBa2Cu3O7 that becomes superconducting above liquid nitrogen temperatures (Tc = 90K). Using a cubic neodymium magnet 4mm of side, two effects can be shown. Firstly, the Meissner effect itself, by placing the magnet on the...

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The Surface Treatment of Glass

What it shows:

The strength of a material in tension or compression will be affected by discontinuities in its surface structure. This can be demonstrated for glass using microscope slides, and the comparison of failure stress before and after the removal of surface scratches.

How it works:

The slide rests between two custom built test beds (figure 1), the upper bed supporting the load. We use slotted 1kg and 0.5kg masses placed carefully in their holder, and allowing a short time between additions. We find the breaking...

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Supersaturation and Crystallization

What it shows:

A supersaturated solution is unstable, and by seeding it you can trigger rapid crystallization.

How it works:

Sodium acetate can dissolve in water in great quantities at high temperature, and if you let the solution cool carefully to around room temperature, you have a clear supersaturated solution. Disturbing this unstable equilibrium by dropping a small crystal of sodium acetate into the solution makes the whole thing solidify; the sodium acetate crystals growing radially outwards from the impact point of the...

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Liquid Crystal Sheets

What it shows:

The selective reflection of a specific wavelength of light through a chiral nematic liquid crystal is temperature dependent and forms the basis for LCD thermograms and thermometers.

How it works:

Liquid crystals are an intermediate state of matter or mesophase between (crystalline) solid and liquid. Substances that have a mesophase have a non-flexible rod-like molecular structure. Although in a liquid phase, the shape of the molecule and intermolecular forces means that the molecules retain a common preferred...

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Dilatancy of Deformation

What it shows:

When sand in a balloon, just as atoms in a lattice, are close packed, they occupy the least possible volume. Any deformation, even compression, deforms this close-packed arrangement causing an increase in volume.

How it works:

The balloon is filled with sand, and black ink added allowed to percolate down and fill the air gaps. A capillary tube sticking out of the balloon indicates the ink level. When the balloon is squeezed the sand, which had settled down to a closely packed arrangement, is dislocated. Larger gaps...

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Crystal Growth & Recession

What it shows:

By providing a cold boundary, you can get water to crystalize as advancing needles of ice.

How it works:

This cold boundary can be provided by a petri dish of alcohol. Adding dry ice to this produces an endothermic reaction that lowers the temperature below 0°C. By placing a smaller petri dish containing distilled water within the alcohol dish (figure 1), the water freezes from the outer edge inwards. In front of a "thick" wall of ice shoots a monolayer of needles. The advance or recession can be...

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Meissner Effect

What it shows:

A superconducting material in the presence of an external magnetic field excludes that field from its interior. This is shown by levitating a magnet above a high-temperature superconductor.

...

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