001, Mystery Boxes
Students manipulate opaque, sealed containers in an attempt to describe the container's contents.
Go to Top Key words
002, Density of Methanol versus Density of Water
A U-tube is filled with two different liquids under the illusion that only one liquid is being used. The liquids selected have different densities. A taller column of the less dense fluid is observed. Students are asked to predict the outcome of some operation under circumstances where they are likely to operate under an illusion or jump to a conclusion based upon their experience with everyday situations. The most usual case is to show the tube partly filled with identical levels in each arm and ask what will happen when more liquid is added to one arm.
Go to Top Key words
003, Floating Solid
Students often operate with the misconception that solids sink when placed in liquids. When a hole is drilled in a paraffin disc, students unfamiliar with the properties of paraffin are surprised that the disc does not sink when placed in a container of water.
Go to Top Key words
004, Densities of Warm and Cool Water
Using ordinary running tap water, a dramatic consequence of the density difference between warm and cool water is demonstrated by dyeing the water and layering cool water above warm and vice versa.
Go to Top Key words
005, Observing Reactions
Two seemingly identical sets of chemicals are provided for student study. Students observe systematically the results of combining the chemicals. When sharing the results with an entire class, debate regarding the differences in observations often ensues.
Go to Top Key words
006, The Blue Bottle
One solution is divided between two containers (flasks) such that one container is nearly full and the other nearly empty. Shaking the filled container does not seem to produce a dramatic change, but shaking the partially-filled container does. Pouring the liquids from the filled container to the empty one and repeating the procedure leads to the same result -- only the nearly empty container gives a dramatic change.
Go to Top Key words
007, Bunsen Burner
Burners and flame properties are demonstrated.
Go to Top Key words
008, The Non-Candle
Materials that look and burn very much like an ordinary candle are used to illustrate the effects which one's experience and expectations have upon the observations they make.
Go to Top Key words
009, Introduction to Measurement
A wide-ranging series of measurements is undertaken by students during what might be termed a 'measurement fair.' Measurements include traditional quantities such as length as well as nontraditional quantities such as the time it takes to count out a particular pile of beans.
Go to Top Key words
010, Precision
Students repeat a measurement and record data. They study the reproducibility of their own measurements and compare their results to those of classmates.
Go to Top Key words
011, Measurement of Density
Several measuring techniques are applied to determine the density of an object. The concept of density is explored. Archimedes' principle is introduced, and a Cartesian diver is demonstrated.
Go to Top Key words
012, The Density of Liquids and Solids
Common liquids and solids of various densities are layered in a beaker. The liquids form different layers and the solids float at the interfaces between them. This demonstrates that a solid's ability to float or sink depends on its density relative to the liquid it is in.
Go to Top Key words
013, The Use of a Dial-o-Gram¨ Balance
The use of a Dial-o-Gram¨ balance is explained, including reading of the Vernier scale.
Go to Top Key words
014, Mass and Weight
Two balls of different mass but similar size are dropped from a table top. They strike the floor at the same time. When the same balls are accelerated using air from a hair dryer, the less massive ball accelerates more rapidly than the more massive one.
Go to Top Key words
015, Intensive versus Extensive Properties
Intensive properties (temperature, pressure) do not depend upon the sample size. Extensive properties (mass, volume) depend upon sample size. Two identically sized portions of a solution are prepared. One portion is then arbitrarily subdivided into three subportions. For intensive properties, the value of the property for each subportion is the same. For extensive properties, the sum of the values of the property for the subportions equals the value for the whole portion.
Go to Top Key words
016, Introduction to Atomic Mass
Students will find the "atomic mass" of three different types of objects -- peas, beans, and rice. Each of these objects is too small to mass accurately one by one, so a larger sample is massed and divided by the number of objects in the sample to find the individual mass. The calculated "atomic mass" is then used to estimate the number of objects in a sample of known mass.
Go to Top Key words
017, One Mole
One mole of each of many different substances are put in plastic sacks and displayed on a bulletin board to demonstrate that moles of different substances can have different masses and volumes.
Go to Top Key words
018, Formula of a Hydrate
A sample of hydrated compound is weighed. It is then heated to drive off moisture and reweighed to constant weight. All of the mass loss is assumed to be due to water of hydration. From the initial and final masses, the formula for the hydrate is determined.
Go to Top Key words
019, A Silver/Copper Replacement Reaction
Copper wire reacts with aqueous silver nitrate. The relative amounts (moles) of reactant and product are determined from the mass loss of copper wire, the starting mass of silver nitrate, and the mass of silver metal obtained.
Go to Top Key words
020, Reduction of Copper(II) Oxide
Black copper oxide is reduced to form copper metal (with its characteristic appearance) using methane gas. The reaction is clean and stoichiometric.
Go to Top Key words
021, Stoichiometric Double Check
A reaction in which it is possible to determine the masses of several reactants and products is conducted. A gaseous product is determined by mass lost from solution. One reactant mass and one product mass are determined directly.
Go to Top Key words
022, Isotope/Element Model
Prior to 1982, US pennies were made of an alloy containing mostly copper with some zinc. Since 1982, US pennies have been made by electroplating zinc blanks; these coins contain very little copper. The "copper" pennies have a significantly larger mass than the "zinc" pennies. Also, the copper pennies are unreactive to acid when scratched. Under similar conditions, the cores of the "zinc" pennies dissolve away yielding very thin copper foils which bear the image of a penny. This experiment develops some relationships between pennies and isotopes.
Go to Top Key words
023, Mole Map Model
The mass and volume of 144 uniform objects are determined. Based upon these measurements, the mass and volume of one object are determined, as are the mass and volume of a gross of objects. The analogy involves extending one gross to one mole, and changing the objects from visible, macroscopic particles to atoms.
Go to Top Key words
024, Limiting Reagent
Equal numbers of moles of acid are placed into each of three vessels. Different amounts of sodium bicarbonate are reacted with the acid. In the middle vessel, equal numbers of moles of acid and bicarbonate are present. In the first vessel there is excess acid; in the third vessel there is excess bicarbonate. By capturing the gas released in balloons, students can see differences in the number of moles. Mixing unreacted materials confirms the presence of excess chemicals.
Go to Top Key words
025, Electrical Nature of Matter
Charges are produced by rubbing plastic strips. The interaction of the charges are observed using pith balls, electroscopes, and the strips themselves. The interaction of scraps of paper with a pocket comb pulled through hair is observed.
Go to Top Key words
026, Beanium
Beanium is an imaginary element whose atoms are macroscopic. The Beanium model is based upon an analogy to isotopes.
Go to Top Key words
027, Atomic Spectra
A quantitative analysis of the hydrogen spectrum is made and interpreted. Other spectra are examined and discussed qualitatively.
Go to Top Key words
028, Resonating Air Column; Metal Rod
A tuning fork held above a column of air causes a resonant sound for certain column lengths. A metal rod held at its center vibrates with a loud, characteristic sound when "stroked." The frequency of the sound can be changed by changing the point of support.
Go to Top Key words
029, Energy Level Simulator with Magnets
Face-polarized ring magnets are placed on a shaft with like poles facing one another. The levitating magnets are a model for systems with well-defined energy states.
Go to Top Key words
030, Patterns in Nature
One practice learning activity to develop the ability to recognize patterns is to group words (nouns; verbs) so that they reflect existing relationships. The nouns used to illustrate this lesson include moving vehicles. Some move through air, others in water, and others on land. Students should be able to recognize a distinct pattern in their grouping so that, when a new word is added, it can be placed into an existing category. Many groupings are appropriate. This sorting activity is intended to precede instruction on the periodic chart.
Go to Top Key words
031, Probability
Students drop steel spheres onto a target. They measure the resulting distribution of points, and plot those points on a graph.
Go to Top Key words
032, Periodicity of Properties
A wide range of chemical reactions is performed, and the acid/base properties of the products are studied.
Go to Top Key words
033, Significance and Use of the Periodic Table
This is a dry-lab, hands-on activity where students must arrange elements according to properties.
Go to Top Key words
034, Atomic Model
A styrofoam model is presented that incorporates the ideas of the ancient Greeks, Dalton, Bohr, Rutherford, and Schrodinger.
Go to Top Key words
035, Projection Spectroscope
Opaque cards are used to produce a slit or beam of light from an overhead projector. The light emitted from the projector is passed through a plastic grating sheet. Examination of the dispersed light resulting from this process gives clues regarding light absorption.
Go to Top Key words
036, Chemical Bonding in Solids
Several substances are studied with respect to properties such as solubility and melting temperature in an attempt to ascertain the classify chemical bonding characteristics of solids.
Go to Top Key words
037, Physical Properties and Chemical Bonding in Solids
Solubility and conductivity experiments are performed with sodium chloride, p-dichlorobenzene, silicon dioxide, and iron.
Go to Top Key words
038, Displaying Structures in Two Dimensions
This is a teacher-oriented demonstration of the use of two audio visual techniques: flannel boards; and cut-outs at the overhead projector.
Go to Top Key words
039, Shapes of Covalent Molecules
To practice drawing Lewis structures for molecules, predicting shapes from these drawings, and building appropriate models.
Go to Top Key words
040, Three Dimensional Structures of Molecules
Balloons are used to illustrate the valence shell electron pair repulsion model for predicting molecular shapes.
Go to Top Key words
041, Hydrogen Bonds and Dipole Forces
Models containing magnets are constructed from ordinary materials. The magnetic interactions cause different models to become "sticky," and thereby permit the illustration of hydrogen bonding and dipoles forces.
Go to Top Key words
042, Arrangements of Particles in Crystals
Styrofoam models are built to illustrate cubic closest packing, hexagonal closest packing, body-centered cubic, and simple cubic crystal structures. The sodium chloride lattice is also demonstrated.
Go to Top Key words
043, Bonding Model for Projection
Models consisting of pieces of transparent, colored plastic glued to face polarized ring magnets are shown using an overhead projector. By using different arrangements of magnets, the interactions of various arrangements are demonstrated.
Go to Top Key words
044, Electrolysis of Water
Water containing a dissolved salt is electrolyzed in an apparatus where the volumes of gas produced can be collected and measured. The gaseous products are tested and identified.
Go to Top Key words
045, Preparation and Sublimation of Iodine
Elemental iodine is prepared in small amount through the oxidation of an iodide compound with manganese dioxide. The iodine is sublimed by heating the reaction vessel and crystallizing the iodine vapor using an ice-cooled watch glass.
Go to Top Key words
046, Sodium in Water
A small piece of metallic sodium is placed in a dish of water containing phenolphthalein on an overhead projector stage. The sodium reacts vigorously, melts, and sputters on the surface of the water as a sphere of continuously decreasing size until it has completely reacted. The moving sodium leaves a pink trail in the water.
Go to Top Key words
047, Electrolysis
A variety of solutions are electrolyzed using an apparatus constructed from pencils and a 9-volt battery.
Go to Top Key words
048, Combustible Powders
A combustible powder is injected into a closed vessel that contains a burning candle. An explosion ensues.
Go to Top Key words
049, Methane Combustion in a Can
A combustible gas is placed in a can with constricted openings. Gas emerging from the can is ignited. The gas burns with a flame whose characteristics change as the composition of the gas changes. Ultimately, the gas reaches critical explosion limits and a small explosion ensues.
Go to Top Key words
050, Combustion of Ethanol
A few cmÜ of combustible liquid are placed in a plastic container equipped with two large electrodes made from nails. After time is allowed for the liquid to evaporate, a spark provided to the electrodes from a Tesla coil causes an explosion.
Go to Top Key words
051, Hot Penny Catalysis
A piece of copper metal heated to red heat, when placed in the vapor of an oxidizable alcohol, continues to glow red as the result of continuing oxidation and the attendant release of heat.
Go to Top Key words
052, Catalyzed Burning of Sucrose
A cube of ordinary table sugar (sucrose) does not burn readily. When ashes (a source of alkali) are rubbed on the surface of the cube, however, it burns easily.
Go to Top Key words
053, Red, White, and Blue Colors
Aqueous ammonia is added to each of three beakers in which reactions take place to form products that are colored red, white, and blue, respectively.
Go to Top Key words
054, Reactions of Copper
Copper metal is dissolved in nitric acid. The copper in the copper nitrate solution is converted into copper hydroxide which, upon heating, is converted into copper oxide. The copper oxide is dissolved in acid, and the resulting solution is treated with zinc metal to produce copper metal. This is not performed as a quantitative experiment.
Go to Top Key words
055, Oxidation States of Manganese
Solutions of manganous ion(+2) and permanganate ion(+7) are used to prepared samples of other manganese oxidation states.
Go to Top Key words
056, Preparation of Oxygen
Oxygen is prepared through the action of solid manganese dioxide on a solution of 6% aqueous hydrogen peroxide.
Go to Top Key words
057, Equilibrium Crystallization
Unsaturated, saturated, and supersaturated solutions of sodium acetate are prepared. When seed crystals of sodium acetate are added to each, they dissolve in the unsaturated solution, they remain at equilibrium in the saturated solution, and they bring about the complete solidification of the liquid in the supersaturated solution.
Go to Top Key words
058, Supersaturation
A supersaturated solution is treated with a seed crystal. When introduced into the solution, the entire mass of the solution solidifies. When poured over a seed crystal, a solid mass forms on top of that crystal.
Go to Top Key words
059, Solubility of Ammonia in Water
Flasks filled with dry ammonia gas are submerged under water and opened. Indicators may be used. This experiment may be scaled down and performed by students in two ways. First, they may fill bulbs of plastic transfer pipets with ammonia and use these for study. Second, they may stack two identical vessels. A few drops of concentrated ammonia are placed in one. A few drops of phenolphthalein are placed in the second. The second vessel is then filled with water, covered with a piece of filter paper, inverted, and stacked over the first vessel. Ammonia from the lower vessel rapidly passes through the gas phase into the upper vessel producing spectacular plumes of red-pink color.
Go to Top Key words
060, Molar Concentration
Measured volumes of acid solution are allowed to react with insoluble substances (CaCO2, Zn). By measuring the mass of insoluble material dissolved as the result of reaction, the number of moles of acid is determined. From the moles and volume of acid, the molar concentration is determined.
Go to Top Key words
061, Aqueous and Nonaqueous Solvents
Cobalt chloride is dissolved in water, in ethanol, and in acetone. The colors are noted. The resulting organic solutions are treated with water and color changes are noted.
Go to Top Key words
062, Electrical Conductivity
The electrical conductivities of solutions of strong electrolytes, weak electrolytes, and nonelectrolytes are studied. This experiment is performed as a demonstration when the older and more dangerous conductivity apparatus is used. It may be performed as a student experiment when new apparatus is constructed.
Go to Top Key words
063, Solubility and Ionic Reactions
A variety of aqueous solutions of substances are combined, two at a time. These combinations permit rules for solubility to be generated. Two alternative procedures are suggested, the first of which enhances analysis skills as well as skills for writing net ionic equations.
Go to Top Key words
064, Solution Formation
The solubilities and miscibilities of several solvents are studied.
Go to Top Key words
065, The Effect of Temperature on Solubility
Students are given weighed samples of a soluble salt such as potassium nitrate. The sample is added to 20 mL of water and heated until all of the salt dissolves. The solution is cooled, and the temperature at which solid appears is noted. A solubility curve is prepared by pooling the data from all of the students.
Go to Top Key words
066, Colligative Properties
The freezing temperatures of distilled water, a solution of a nonelectrolyte such as sucrose, and a solution of an electrolyte such as calcium chloride are determined. From the resulting data, regularities in the freezing properties of solutions are discovered.
Go to Top Key words
067, Cooling Behavior of a Solution
This experiment is very similar to 066, Colligative Properties. Students use acetamide (CH3CONH2) as the solvent. Acetamide has the advantage over water of giving a much larger freezing point depression per mole of dissolved solute. Also, it is a polar solvent in which ionic substances dissolve and dissociate.
Go to Top Key words
068, Surface Tension
Powdered sulfur is dusted on the surface of some clean water; it floats. Upon the addition of a small amount of detergent, the sulfur wets and sinks. Dyes puddle when added to the surface of whole milk, but begin mixing in dramatic, colorful streaks when a drop of detergent is added to the container wall near the upper surface of the milk. Nearly 1 cm of liquid film may be drawn up from the surface of liquid water using a ring and a triple beam balance. These three phenomena illustrate some of the consequences of surface tension.
Go to Top Key words
069, Producing a Foam
A foam consisting of a gas dispersed throughout a liquid is produced when carbon dioxide is generated in a liquid.
Go to Top Key words
070, Mixing Alcohol and Water
A long, narrow tube is filled half-full with water containing some food coloring. The tube is then filled to the top with alcohol colored with different food coloring. The ends of the tube are stoppered. The tube is inverted repeatedly until mixing is complete as judged by the color change. The formation of a gas bubble is noted, as is the release of heat.
Go to Top Key words
071, Combining Stoichiometry
Using 12-wells strips, different amounts of equimolar solutions are mixed. The volume of solid produced is observed. The maximum volume of solid is produced when the ratio of the combining volumes equals the ratio of coefficients from the balanced chemical equation. 072, Determination of Absolute Zero
A gas pressure gauge connected to a metal container tells the pressure of the gas inside. By heating the gas above (and cooling it below) room temperature, the quantitative relationship between pressure and temperature is determined.
Go to Top Key words
073, Pressure versus Volume in a Gas
A closed apparatus, which traps air in a calibrated glass vessel over mercury, is used to measure the pressure and volume of a gas sample. The system is designed so that the pressure applied can be adjusted by raising or lowering a bulb filled with mercury. The volume occupied by the gas and the levels of both the internal and external mercury surfaces can be measured. From these data together with the barometric pressure a quantitative relationship between pressure and volume is obtained.
Go to Top Key words
074, Boyle's Law Using a Capillary Tube
A glass capillary tube sealed at one end is plugged about half-way down its length by a 3 cm plug of liquid mercury metal. When held in a horizontal position, the plug has no effect on the pressure of trapped gas. When held vertically, open end up, the plug adds to atmospheric pressure. When held vertically, open end down, the plug subtracts from atmospheric pressure. Data for gas volume, the length of the plug, and barometric pressure are analyzed to discover a quantitative pressure-volume relationship for gases.
Go to Top Key words
075, Volume versus Pressure in a Gas
Air is trapped in a syringe (an air piston). By clamping the sealed syringe upright and adding weights to the plunger, the pressure exerted on the trapped air is varied systematically. The mass applied and the resulting volume are recorded. The data permit the determination of a relationship between volume and pressure for a fixed mass of gas at constant temperature.
Go to Top Key words
076, Relationship of Gas Temperature and Volume
A liquid mercury plug traps some gas in a sealed glass capillary tube. As the gas is heated, it may change its volume by moving the mercury plug. (A similar apparatus was used to demonstrate Boyle's Law in 074.) From the data obtained, the relationship between the volume and temperature of a fixed mass of gas at constant pressure is determined.
Go to Top Key words
077, Determining the Molar Mass of Butane
A sample of butane gas (isobutane) is obtained from a disposable cigarette lighter. The lighter is weighed both before and after the gas is withdrawn. The volume, temperature and pressure of the gas are measured. From these four quantities, the molar mass of the gas is calculated. This is shown as a lecture experiment, but can be performed as a student experiment when balances of adequate sensitivity (0.001 g) are available.
Go to Top Key words
078, Determining the Molar Mass of a Vapor
A volatile liquid with a boiling temperature in the range of 70-90 °C is placed in a small, dry, weighed flask. The mouth of the flask is covered with aluminum foil. A small hole is pierced through the foil. The flask is heated in boiling water until the liquid boils, and for a few seconds thereafter. At that point, the entire space of the flask is filled with vapor at 100 °C. The flask is cooled, dried, and weighed. The volume of the flask is measured. From all these data, together with the barometric pressure, the molar mass of the volatile liquid is calculated.
Go to Top Key words
079, Molar Volume of a Gas
A meter of polished magnesium is weighed. Lengths of the ribbon are cut. The length of a small section is measured, and the mass calculated from the length. The small section is dissolved in acid such that all of the gas is captured in a buret. From the volume of the gas, the pressure, the temperature, and the mass of magnesium, the molar volume of magnesium is calculated. A microscale version of this experiment is available.
Go to Top Key words
080, Graham's Law of Diffusion
Hydrogen chloride and ammonia diffuse from opposite ends of a long tube. They meet and react to produce ammonium chloride, a white solid powder. The distances of the white powder from either end of the tube are measured, and the ratio compared with a predicted ratio from Graham's Law. The experiment is not expected to give close quantitative agreement between calculated and observed values, but the ammonia does diffuse faster than the HCl, as expected.
Go to Top Key words
081, Air Bubble in Carbon Dioxide
A soap bubble falls to the bottom of an open tank filled with air. When the same tank is filled with gaseous carbon dioxide, a similar bubble floats.
Go to Top Key words
082, Weighing Carbon Dioxide Gas
A balance is constructed with a 'beam' from a meter stick and "pans" from large, low-weight brown paper grocery bags. The pivot point is a hole in the center of the meter stick balanced on a nail or other suitable cylindrical object. When carbon dioxide gas is "poured" into one of the bags, it displaces air. That pan becomes heavier and moves downward.
Go to Top Key words
083, A Speed Distribution
Heating liquid mercury causes small plastic chips floating on the mercury surface to receive energy and fly around inside a sealed tube. It is apparent that not all of the chips fly at the same speed; some fly much faster than others. This analogy is used when teaching about speed distributions in gaseous molecules.
Go to Top Key words
084, Methane Bubble; Rising Cinder
A soap bubble filled with methane gas rises in air. The bubble may be ignited; it burns quietly with a luminous flame. A piece of paper from the inside of a ditto master is ignited. When nearly completely burned, the hot cinder rises in air. (This experiment is sometimes called the paper rocket.)
Go to Top Key words
085, Molar Volume Model
Students construct models of different shapes whose total volume is 22.4ÊL.
Go to Top Key words
086, Dihydrogen Diffusion
An apparatus is constructed so that dihydrogen is able to diffuse into a flask and thereby increase the gas pressure forcing liquid to be expelled from the flask through an exit tube. When the source of dihydrogen is removed, the dihydrogen escapes more rapidly than air can replace it and air is drawn in through the same tube.
Go to Top Key words
087, Dry Ice in a Balloon
Solid dry ice is placed in a balloon. It sublimes, and the resulting gas occupies a much larger volume than the solid; the balloon expands greatly, and often bursts. When a balloon is filled with a gas more dense than air, the balloon may serve as a lens focussing sound and giving the effect of amplifying the sound. Speaking through the balloon to the class demonstrates this effect.
Go to Top Key words
088, The Collapsing Can
When heated enough to boil water, a soda can becomes filled with water vapor at atmospheric pressure. When cooled suddenly, the vapor pressure drops substantially below atmospheric pressure. Either the can will collapse, or water will be pushed into the can. Aluminum soda cans usually collapse in a spectacular fashion.
Go to Top Key words
089, Vapor Pressure and Manometry
A closed system consisting of a filter flask is connected to a manometer tube. When 20 mL of air is injected into the flask, a dramatic change occurs in the manometer levels. When 0.1 mL of a volatile liquid is injected, a similar change occurs.
Go to Top Key words
090, Boiling Water Under Reduced Pressure
Three methods are shown. First, a vacuum pump is used to lower the pressure of water at room temperature. Second, hot water is placed in a large syringe. When the end is sealed, pulling on the syringe barrel causes the pressure to be lowered so that the hot water boils. Third, water is heated to boiling in a flask. The heat is removed, and the flask stoppered. When ice is applied to the flask, the pressure is lowered and the water boils.
Go to Top Key words
091, Cooling Curves
A melted solid is cooled. The temperature and time for the cooling process are measured. A cooling curve is constructed from this information.
Go to Top Key words
092, Balloon-Filled Flask
A small amount of liquid water is placed in an Erlenmeyer flask. The water is boiled. The flask is removed from the heat source and covered with a balloon once the water is boiling. Most of the gas in the sealed system is water vapor. When the vapor cools and condenses, air pushes the balloon into the flask.
Go to Top Key words
093, Endothermic and Exothermic Reactions
A small amount of water soluble salt is placed in a test tube. A small amount of water at room temperature is added. A change in temperature is sensed by a finger. When the temperature changes, one of the terms (exothermic or endothermic) is applied to describe the reaction.
Go to Top Key words
094, Energy Needed To Melt Ice
Ice at 0 °C is added to a measured volume of warm water. Some of the ice melts. Once the mixture reaches 0 °C, the volume of liquid water is measured. The additional volume comes from melted ice. Using the amount of ice melted together with the temperature and volume of warm water, the heat of fusion of the ice is determined.
Go to Top Key words
095, Heat of Solution of Magnesium
The mass of a measured length of polished magnesium ribbon is determined. A small length of ribbon is cut and its length measured. From the length of the small piece, its mass is calculated. A known volume of acid is placed in a calorimeter. The temperature is measured. The magnesium is added to the calorimeter, and a reaction takes place. The temperature is measured once reaction ceases. From the mass of ribbon reacted, the temperature increase, and the volume of acid used, the heat of formation of Mg2+(aq) is determined.
Go to Top Key words
096, An Endothermic Reaction
Mixing barium hydroxide solid with ammonium chloride or ammonium thiocyanate at room temperature leads to a spontaneous reaction that is so endothermic as to cause water to freeze.
Go to Top Key words
097, Reaction in a Bag
Equal volumes of anhydrous calcium chloride and sodium bicarbonate are placed in a sealable plastic bag. Aqueous phenol red is added, the bag is sealed, and the ensuing reaction is observed.
Go to Top Key words
098, Colorful Reactions of Red Cabbage Juice
Cabbage juice is placed in a large flask. Vinegar is added to the point of color change. Aqueous ammonia is then added to the point of color change. Vinegar is then added again to show the reversibility of the color change.
Go to Top Key words
099, Cabbage Juice Indicator
Red cabbage juice is mixed with a series of buffers to obtain a set of color standards. Various household substances are added to red cabbage juice. By comparing the color of the resulting solution to that of the color standards, the approximate pH of the household materials is determined.
Go to Top Key words
100, A Qualititative Study of Indicators
A series of solutions of pH 1 through 12 is prepared, and pH indicators are added systematically. From the resulting information, the pH range of each indicator is determined.
Go to Top Key words
101, Indicator Change Points
A solution containing two indicators is titrated. By choosing concentrations and indicators judiciously, it is possible to show that one indicator changes color before another.
Go to Top Key words
102, Standardization of Acids and Bases
Solutions of known concentration are prepared by dissolving measured masses of standard acids in distilled water. The concentrations of unknown solutions of sodium hydroxide are determined by titration.
Go to Top Key words
103, Titration Using A pH Meter
Solutions of sodium hydroxide are standardized by titration of measured masses of standard reagents in water. These standard sodium hydroxide solutions are used to titrate unknown solutions of strong acids (HCl) and weaks acids (CH3COOH). The endpoint is detected with a pH meter.
Go to Top Key words
104, Conductivity of Acids and Bases
An LED device or a meter device is used to study the conductivity of solutions of acids and bases. Changes in conductivity associated with the titration of sulfuric acid by barium hydroxide are studied.
Go to Top Key words
105, Buffers
Indicators are added to dishes of water and buffer. These are "titrated" on an overhead projector. The effect of the buffer in resisting change to pH on the addition of either acid or base is demonstrated.
Go to Top Key words
106, Bronsted/Lowry Acids and Bases
Universal indicator pH test papers are used to determine the pH of solutions of salts.
Go to Top Key words
107, Carbon Dioxide as an Acid
Dry ice is used as a source of carbon dioxide. The carbon dioxide changes the color of indicator solutions prepared in very dilute ammonia. The carbon dioxide may be used to form a precipitate of calcium carbonate. Continued addition of carbon dioxide causes the calcium carbonate to redissolve. This experiment may be performed as a demonstration or as a student experiment on the microscale.
Go to Top Key words
108, Effects of a Buffer
Two solutions of acetic acid are prepared, one of which contains a large amount of sodium acetate. Equal amounts of magnesium metal are added to each solution. Both solutions produce the same volume of dihydrogen gas. The buffered solution produces the dihydrogen more slowly.
Go to Top Key words
109, One Pot Silver Reactions
A series of reactions is performed in a sequence such that a visible change appears in a system. First, solid silver carbonate precipitate is produced. It is tan in color. This precipitate is dissolved in ammonia to give a colorless solution. Sodium chloride produces a white precipitate which dissolved in sodium thiosulfate to give a colorless solution. Sodium iodide gives a yellow solid that turns black on the addition of sodium sulfide.
Go to Top Key words
110, Chromate-Dichromate Equilibrium
Acids and bases are added to a system so as to shift the position of a chemical equilibrium. Color changes permit the student to infer which concentrations are changing and to use Le Chatelier's principle to predict the changes.
Go to Top Key words
111, Changing Position of a Gaseous Equilibrium
Gaseous nitrogen dioxide is trapped in the barrel of a closed syringe. The total gas pressure of the system can be changed by moving the syringe piston. The dark nitrogen dioxide is in equilibrium with colorless dinitrogen tetroxide. The effect of changing the pressure (volume) on the position of this equilibrium can be studied.
Go to Top Key words
112, First Order Reaction Analogy
A known number of pennies is placed in a box. The box is covered and shaken. All of the pennies with tails up are removed and the number counted. The box is reclosed, reshaken, and all of the tails-up pennies removed and counted. This process is repeated until very few pennies remain in the box. The data is used to illustrate a first order reaction.
Go to Top Key words
113, Temperature and Reaction Rate
Light sticks that use chemiluminescent reactions to glow in the dark are placed in reaction baths at different temperatures. Sticks in the hot bath give off much more light than those in room temperature baths. Sticks in cold baths give off the least light.
Go to Top Key words
114, MicroScale Iodine Clock Reaction
A kinetics experiment is performed in such a way that a fixed amount of a reagent is consumed by a product of a slow chemical reaction. The time required for a fixed amount of thiosulfate to be used up is measured and related to the concentration of one of the reactants, hydrogen peroxide. From this information, the order of hydrogen peroxide in the reaction is determined.
Go to Top Key words
115, Le Chatelier's Principle
Le Chatelier's principle, a chemical system at equilibrium will respond to a change so as to "undo" part of the effect of that change, is studied using saturated sodium chloride solutions and concentrated hydrochloric acid. Adding concentrated hydrochloric acid to a saturated sodium chloride solution causes solid sodium chloride to precipitate. Adding distilled water reverses the effect.
Go to Top Key words
116, Copper/Zinc Galvanic Cell (Daniel Cell)
The spontaneous chemical reaction between zinc metal and aqueous copper(II) sulfate is conducted so as to obtain the available chemical energy released in the form of electrical energy.
Go to Top Key words
117, Aluminum Oxygen Galvanic Cell
The spontaneous chemical reaction between aluminum metal and dioxygen is conducted so as to obtain the available chemical energy released in the form of electrical energy. This is a particularly interesting example of the importance of materials science.
Go to Top Key words
118, Laser Aided Determination of Ksp and Kstab
The determination of equilibrium constants for solid/solution equilibria is difficult when a judgment is to be made about when the solid has formed. A laser is used to create Tyndall scattering from an otherwise invisible amount of precipitate. The appearance of the scattering permits determination of Ksp; disappearance of the scattering permits determination of the stability constant of the silver ammine complex.
Go to Top Key words
119, Water Tank Equilibrium Analogy
Two tanks are filled with water. Two students are provided with cups. Each student is given the objective of 'emptying' their assigned tank by scooping water from it and transferring that water to the other student's tank. The sizes of the tanks and cups determine the level of water that each tank will hold once 'equilibrium' is reached. Teachers find this to be a useful analogy when discussing the concept of a dynamic equilibrium and the factors that affect equilibrium position.
Go to Top Key words
120, Building and Testing a Blocktronic I Colorimeter
An inexpensive device is constructed from readily available materials that permits the monitoring of the optical density of a solution. The device is constructed so as to connect directly to the game port of an Apple IIe or Apple IIgs computer.
Go to Top Key words
121, Assembling and Testing Thermistor Probes
A pair of thermistor probes is assembled and tested prior to calibration. The probes are assembled with a 9-pin D-connector for direct attachment to the game port of an Apple IIe computer.
Go to Top Key words
122, Thermistor Calibration
A systematic calibration procedure is applied to thermistor probes.
Go to Top Key words
123, Apple Game Port Adapter Cable
The assembly of this cable allows 9-pin male D-connectors, designed for the external port of an Apple IIe (IIc, or IIgs), to connect to older computers with an internal 16-pin connector is described.
Go to Top Key words
124, Simple Heat of Acid/Base Reaction
Using a simple styrofoam calorimeter and with the computer as a temperature measuring device (i.e., a thermometer), the heat of an strong acid-strong base reaction is measured.
Go to Top Key words
125, Change of Phase in Glauber's Salt
A sample of Glauber's salt (Na2SO4•10H2O(c)) is heated above the phase transition temperature. The temperature of the melt is recorded as the melt cools and solidifies.
Go to Top Key words
126, Cooling and Heating Curves
A solid that melts in the temperature range 50-70 °C is melted. The temperature of the melt is recorded while the melt cools to room temperature.
Go to Top Key words
127, Job's Method Thermal Titration of Acids and Bases
Two titrations are conducted by the incremental addition of acid and base. When a base is titrated with an acid, the acid is added in several portions. the temperature is recorded for each increment. A plot is made of temperature rise from the beginning of the titration to that point versus the volume added. The titration is then carried out with the other order of addition. The intersection of the two temperature/ volume curves is related to the combining stoichiometry of the acid and base.
Go to Top Key words
128, Gas Chromatography
Gas chromatography is a technique in which mixtures are separated into components on the basis of differences in vapor pressure and interaction with a stationary phase and a mobile phase. This experiment uses a solid detergent as the stationary phase and natural gas as the mobile phase. The natural gas is burned in a flame as it emerges from the apparatus. The substances selected for separation contain chlorine which reacts with hot copper metal to give a bright green color in the flame of burning mobile phase and thus permits detection of the separated species.
Go to Top Key words
129, Beer's Law
For many colored materials there is a linear relationship between a property of the materials called optical density and the concentration of the colored species. The linear relationship is called Beer's Law. A Blocktronic colorimeter is used to show that Beer's Law holds for ordinary food colorings. Differences in optical density for common sodas are measured. An overhead projector demonstration is used to show how the Blocktronic works in terms of absorbing light.
Go to Top Key words
130, Kinetic Study of Thiosulfate in Acid
The acidification of thiosulfate solutions leads to the formation of colloidal sulfur. This sulfur scatters light in the Blocktronic colorimeter, and permits a quantitative study of the reaction. A hands-on "microscale" chemical version of this experiment is included.
Go to Top Key words
131, A Kinetic Study of the Ferric Ion/Iodide Ion Reaction
Iron(III) ion oxidizes iodide ion with the formation of iodine and triiodide ion. The color appearance is readily followed in a Blocktronic.
Go to Top Key words
132, Kinetics of Crystal Violet/Hydroxide Ion Reaction
Crystal violet undergoes a reaction in which the dye molecules are converted into a colorless substance. This reaction is first order in dye and in hydroxide ion. Crystal violet is a cation and the resulting product is neutral. As a result, the reaction rate is very sensitive to changes in ionic strength.
Go to Top Key words
133, Equilibrium Constant
One useful application of Beer's Law is to determine the equilibrium constant of a reaction. Reactants (iron(III) and thiocyanate) are mixed in a ratio such that one reactant is presumed to be nearly 100% converted into a colored product. The product is assumed to follow Beer's Law, and the relationship between relative absorbance and concentration is determined from the first experiment. After that, the reactant originally in excess is reduced in concentration. From the colorimetric determination of product concentration, the concentrations of reactant remaining at equilibrium is determined and the quantitative relationships among these concentrations are studied. One of these relationships, the mass action expression, is found to be nearly constant.
Go to Top Key words
134, Spreadsheet Software Tools
There are two general situations in which spreadsheets are useful. The first situation applies to cases where students will repeat the same experiment in different ways so that the sharing of data within the group is essential. The second situation is where a series of measurements are taken by one student and the analysis of the results of these experiments is facilitated by the spreadsheet.
Go to Top Key words