The 1827 Christmas Lectures
of Michael Faraday

Demonstration of Lecture #1 Today

Substances -- Solids, Fluids, Gases and Chemical Affinity

Teacher Presentation

Good evening! Welcome to the first of this year's Christmas Lectures adapted for you. Tonight's demonstrations will show how the nature of a substance affects its behavior. All of tonight's demonstrations will be useful in the following lectures, indeed some will be repeated later. I will show you that solids are hard and retain their shape; that liquids are fluid and accept the shape of their container; and that gases are compressible but will return to their uncompressed state with dramatic results. Now let us begin with the first demonstration.

• (Lab. 1-3) A block of wood, a piece of metal and other solid matter will be struck with the hand and these solid materials will retain their shapes. This property is not common to liquids nor gases. However, color, brilliance, and weight are properties of all three states of matter.

  If I place a piece of wood in a container the wood will not adapt its shape to that of the container.

• (Lab. 4-8) However, when we place a liter of water in a differently shaped container, it quickly accepts the new shape without change in composition or amount. As the water is poured from the tall, narrow cylinder into the shorter, bulbous flask, notice also that the amount and appearance do not change but it does not retain its form or shape.

Solids retain their form, liquids do not retain their form but do possess weight and inertia as do solids. Gases are very different. They do have weight but are less likely to resist movement.

• (Lab. 13) When the balloon is inflated, the rubber skin is stretched and the balloon resists the change in shape to a very small degree.

• (Lab. 15) When we hit the bottom of the carboy the gas is pushed through a small opening, which increases its velocity and it travels a considerable distance to blow out the candle.

To show that air has weight we must be a little more imaginative. As you can see, the solids retained shape, volume and inertia; the liquids retained weight, inertia, but not form; and the gas retains only its weight, not its shape and only some of its inertia.

• (Lab. 16) A stick is placed over the edge of the table and is struck on the end. The stick is not held in place by the small amount of air resting on the surface. If we place a sheet of paper over the stick, the amount of air now resting on the sheet of paper is considerably more and it resists the violent movement of the stick. How much weight is resting on the paper?

In addition to the previous properties, gases can be burned. Solids like wood and coal are burned and give off heat and light, liquids such as alcohols and oils burn in much the same manner.

• (Lab. 18) This gas is burned as rapidly or more so than solids and liquids and also produces heat and light. The burning of this gas produces heat and light, evidence of a chemical change.

• (Lab. 20) When Alka-Seltzer is placed in water, a gas is released which is not combustible. This is shown by placing a lighted splint into the test tube, the splint is extinguished.

In summary, solids, liquids, and gases possess many of the same properties and differ only in a few, such as retention of form. All three states of matter can possess color, inertia, weight, and combustibility.

Now we will turn our attention to chemical changes and affinity. For chemical changes to occur, the substances must be attracted to each other. If they are attracted to each other, the chance of a chemical reaction occurring is greatly enhanced.

• (Lab. 24-26) In this reaction, the iron filings are attracted to the magnet. There will be no chemical reaction, but the attraction is similar to the affinity shown by substances that do react chemically.

This large scale affinity is easily seen by the eye, while the majority of chemical reactions are at the micro scale and the affinity is not easily observed. We must therefore demonstrate a change in the macro scale properties of the reacting substances.

• (Lab. 27,30,31) Two powdered white substances are placed in contact with each other. These two substances possess an affinity for each other, demonstrated by a change in color. A new substance is formed.

Let us examine this property of affinity more closely. When similar substances are separated they rejoin easily. Even if the substance is changed from one state to the next.

• (Lab. 32-34) A small amount of gallium metal is melted and placed in a small Petri dish. The liquid is broken into smaller bits. However, the small pieces will rejoin easily.

Now if we take dissimilar substances that have affinity for each other, a dramatic reaction will be observed. The change in properties will be accompanied by the release of heat and light.

• (Lab. 36) Iron filings, like those used with the magnet, are heated and placed in a container of pure oxygen. The iron and oxygen have an affinity for each other, which causes them to react in a very violent manner. (show video)

• (Lab. 38) Video. A white solid is heated and produces several gases with no solid residue remaining. This shows the non-reactivity of non-chemically treated cotton and then chemically treated cotton. The reaction can also be shown in slow motion.

• (Lab. 41) Two colorless solutions are mixed and immediately a dense, intensely yellow precipitate is formed from the speed of the reaction. It is obvious that the two substances have a very strong affinity for each other.

• (Lab. 42-43) Two gases combine and form a solid, because of their affinity for each other.

Many substances dissolve in water, but when the water is evaporated, the original substance is recovered. Sometimes unexpected changes occur, such as placing this metal in water. The chemical and physical properties have been altered.

• (Lab. 51) Show video first. The metal potassium reacts violently with the water. Heat can be shown to enhance the affinity of one substance for another.

• (Lab. 61-63) A small pile of Lycopodium powder is exposed to a flame and nothing much happens. However, when a dust cloud (small particles) is produced, the burning is rapid.

Pressure can have the same effect as small particles size.

• (Lab. 67) A ``cap'' for a cap-pistol is struck. The increased pressure will cause the substances which have an affinity for each other, to react. Even though the substances have an affinity for each other, they are initially not close enough. The compression pushes the particles closer together and also raises their temperature. Only then will their affinity for each other cause them to react violently, producing gases, light, heat and sound.

This concludes my first lecture on solids, fluids, gases and chemical affinity. We wish to invite you back for the next lecture on atmospheric gases, during which I will discuss some of these topics in greater detail.

STATES OF MATTER

Solids

Lab. 1-3: Characteristics of the solid state.

Purpose	To show that solids are hard and that they maintain their shape
Materials	Blocks of wood, pieces of metal, or other solid matter
Procedure	Take the solid materials and show that they maintain their shape when hit with the hand
Hazards	None known - except to hand.

Fluids (liquids)

Lab. 4-8: Liquids take the shape of their containers

Purpose	To show that liquids take on the shape of the container they are placed in.
Materials	1 L graduated cylinder, 1 L volumetric flask, a large funnel
Procedure	Place 1 liter of water in a graduated cylinder and then pour it into the volumetric flask.
Hazards	None known

Gases (distinguished from fluids by their great elasticity)

Lab. 13: Inflating a Balloon

Purpose	To show that an inflated balloon has resistance to being squeezed and can be pressured into different shapes.
Materials	Balloon
Procedure	Inflate a balloon and show that the air in the balloon is elastic, i.e. it can be shaped.
Hazards	None known

Lab. 15: Pop Gun (5 gallon carboy)

Purpose	To show that gases can transport momentum when ``struck''.
Materials	A 5 gallon plastic carboy and a burning candle
Procedure	Hold the carboy so that it is pointed at the burning candle from a distance of 2 meters. Strike the bottom of the carboy sharply with your hand, forcing the air from the carboy to extinguish the candle.
Hazards	None known

Lab. 16: Air has weight (Newspaper & Stick)

Purpose	To show that air has mass and exerts pressure
Materials	A full sheet of newspaper & a stick of wood (approximately 5 mm thick)
Procedure	Place a thin meter stick on a bench with approximately 30 cm of the wood protruding over the edge of the bench. Strike the piece of wood with your hand. Repeat the procedure but not until you have covered the portion of the stick still on the bench with a piece of newsprint. Calculate the weight of the air on top of the newsprint holding it in place (length x width x 14.7 psi).
Hazards	None known

Lab. 18: Some Gases are combustible

Propose	To show that some gases are combustible
Materials	Bunsen burner, flint striker
Procedure	Light a Bunsen burner to show the combustibility of methane CH4 + 2 O2 --> CO2 + 2 H2O
Hazard	Wear goggles and apron and make sure Bunsen burner is adjusted before you begin.

Lab. 20: Some gases are incombustible (Alka-Seltzer)

Purpose	To show that some gases do not support combustion
Materials	250 mL beaker, 30 mL of water, wood splint, Alka-Seltzer tablet, burner or lighter.
Procedure	Place an Alka-Seltzer tablet in a 250 mL beaker containing 30 mL of water. Allow it to begin to react vigorously. Then test with a burning wood splint by placing it in the upper portion of the beaker.
Hazard	Although a potentially edible substance, do not place Alka-Seltzer tablet in mouth or drink liquid.

CHEMICAL CHANGES AND ATTRACTION

Attraction

Macro Scale

Lab. 24-26: Magnet and Iron Filings On Overhead

Purpose	to show macro scale attraction between materials.
Materials	overhead projector, sheet of clear acetate, bar magnet, iron filings
Procedure	Place a bar magnet on the overhead projector, cover it with an acetate sheet and sprinkle the iron filings on top of the acetate.
Hazard	None known

Micro Scale

Lab. 27,30,31: Solid Potassium iodide and lead nitrate

Purpose	To show that two substances can react in the solid state.
Materials	Small glass bottle and stopper, 2 grams each Potassium iodide & Lead(II) nitrate -- finely ground
Procedure	Grind the two solids separately and then place them in the small bottle. Stopper the bottle and shake. 2KI + Pb(NO3)2 --> PbI2 + 2 KNO3
Hazard	Use goggles and apron. Both lead(II)nitrate and lead(II) iodide are toxic by ingestion (lead(II) nitrate dust can be inhaled and is extremely toxic). Special disposal required for lead compounds.

Similar Particles

Lab. 32-34: Hot Gallium

Purpose	To show the attraction which exists between particles of the same material.
Materials	Gallium metal, Petri dish-glass, hot water bath, overhead projector, dropper, small beaker-100 mL
Procedure	Warm the gallium to the melting point and place a few drops of it in a Petri dish which has been placed on an overhead projector. Rotate the dish to allow the drops to combine with each other.
Hazard	This metal has substantial commercial value as scrap. Conserve.

Affinity -- Chemical Attraction

Lab. 36: Iron in Oxygen gas

Purpose	To show the reaction of a solid with a gas. This reaction emits both light and heat.
Materials	Fine steel wool, 1 liter glass bottle or flask -- with stopper -- filled with oxygen gas, burner, crucible tongs
Procedure	Fill a 1 liter glass bottle or flask with oxygen. Lower into the oxygen a piece of steel wool, the end of which has been heated to glowing.
Hazard	Normal precautions to be taken for the handling of hot substances. Pure oxygen is a strong oxidizer-readily supports combustion.

Solid becomes a Gas

Lab. 38: Guncotton video

Purpose	To show the conversion of a solid substance to a gas.
Materials	ACS video cassette ``Close-up on Chemistry''

Liquids become solids

Lab. 41: Lead nitrate & Potassium iodide

Purpose	to show the production of a solid from two liquids
Materials	2-150 mL beakers, a 250 mL beaker, 5g of Potassium iodide, 5g of lead(II) nitrate, distilled water. Prepare two solutions by dissolving 5 g of each reagent in 100 mL of distilled water.
Procedure	Mix together the two solutions in a 250 mL beaker.
Hazard	Both lead(II)nitrate and lead(II) iodide are toxic by ingestion. Goggles and apron should be worn.

Gases become Solids

Lab. 42-43: Hydrochloric acid and Ammonia solution

Purpose	to show that gases can combine and form a solid
Materials	1 Petri dish (disposable plastic), 2 beral pipets, a single drop of concentrated hydrochloric acid, 4 drops of concentrated ammonia solution, overhead projector.
Procedure	Place the bottom half of a plastic Petri dish on the stage of an overhead projector. On the inside edge of the Petri dish, evenly space 4 drops of ammonia solution. Place a very small single drop of concentrated HCl at the center of the other half of the Petri dish. Invert the top half and place it on the half containing the ammonia. HCl + NH3 --> NH4Cl
Hazard	Goggles and apron should be worn. Concentrated HCl is a strong acid and should be handled with care. The ammonia solution is caustic and has a strong irritating odor. However the micro scale quantities used in this demonstration reduce the risk to a minimum. Vapors corrosive to tissue.

Other changes

Lab. 51: Video -- Potassium and Water

Purpose	To show the attraction between water and an active metal.
Materials	ACS Video cassette, ``Close-up on Chemistry''

CAUSES THAT INFLUENCE AFFINITY

Aiding Causes

Division

Lab. 61-63: Lycopodium Powder (pile vs. dispersed)

Purpose	To show the flammability of a finely divided material.
Materials	Lycopodium powder, wire gauze with ceramic center, burner and striker, wood splint
Procedure	Place a small pile of lycopodium powder on the ceramic center of a wire gauze and try to light it with the burning wood splint. Now take the powder and blow or sprinkle some of it into the air surrounding the flame.
Hazard	Goggles and apron should be worn. Normal care to be taken with any flammable substance. Keep bulk lycopodium powder away from flame. Breathing lycopodium dust may cause allergy reaction in some people.

Pressure

Lab. 67: Powder Caps for a cap pistol

Purpose	To show the effect a sudden increase in pressure can have on a substance.
Materials	Caps-suitable for a cap gun, small hammer
Procedure	On a hard surface, place one or two cap-pistol caps. Strike with the hammer.
Hazard	Use blast shield as well as goggles and apron and avoid contact with any flaming object.

Authors

Katherine Anderson, Donald Berry Sr., Gayle Brickert-Albrecht, Ronald Campbell, Damon Diemente, James Ealy, R. Andrew Viruleg, and Nancy Zipprich.

Woodrow Wilson Leadership Program in Chemistry lpt@www.woodrow.org
The Woodrow Wilson National Fellowship Foundation webmaster@woodrow.org
CN 5281, Princeton NJ 08543-5281 Tel:(609)452-7007 Fax:(609)452-0066