Beyond Basic Chemistry

I have assembled here some links to labs I have written which extend the topics covered in an introductory chemistry course. These labs may be used during the school year but several are particularly suited to use at the end of the year.

I have also collected together the handouts I have written for demonstrations which aid in student comprehension by asking them questions and encouraging discussion.

School-year Labs

This at-home lab activity invites students to explore the chemistry of solutions. Boiling point elevation is of particular importance in the making of candy: the boiling point of a sugar solution determines the qualities of the candy product. The true benefit of this lab is that students see that chemistry occurs in their kitchens. And they can eat the products! This lab is best used in the winter, when its cold and hot cocoa may be used for testing the marshmallows.

Marshmallows (at home)

Crystals are ubiquitous but unappreciated by most. In this lab activity students learn about how laundry bluing (a suspension of Prussian Blue) can be used to prevent the formation of large crystals while building incredible structures that take the form of tiny trees. At home students extend their exploration by making decorative ornaments using crystals of Borax. Students will have a chance to learn about the chemistry of super-saturated solutions and the process of crystal formation. This lab is best used prior to the holiday season in case students are so moved as to make holiday-related ornaments or to give their creations as gifts.

Crystals

Students in high school are developmentally ready to learn to think formally. That is, they can, with instruction, learn to think like a scientist. Children readily develop the capacity to walk and to speak their native language. It is not a natural developmental step to observe a phenomenon closely, form a hypothesis, create an experiment to test that hypothesis, and critically evaluate the results. This lab attempts to give students an opportunity to develop these skills. This lab activity can be repeated as many times as the instructor wishes using different phenomena. Several suggestions are given on the online version of the page (these do not print onto the student handout). One that has had particular success concerns buoyancy.

Doing Science

End-of-the-Year Labs

The practice of science can be very regimented. Control and precision are critical to the success of an experiment. The question of flights of fancy or true beauty seldom come up. And yet, an experiment which delicately and definitively alters our fundamental understanding of the world can be a beautiful thing. This lab does not break any new ground but instead uses one of the oldest photographic printing processes to allow students to learn about the chemistry of transition metal complex ions, homolytic bond breakage via UV light, and precipitation of an insoluble pigment known as Prussian Blue. Students create images using the process which gave blue printing its name.

Cyanotypes

Science and its connections to art are explored further in this application of chemistry to the production of paint pigments. Insoluble colored materials, along with a solvent vehicle and a binder, are an important area in industrial chemistry. And yet, they enable artists to create works that move us. In this lab students create several paint pigments, are reminded about stoichiometry, the limiting reactant, and percent yields. The pigments include malachite green; iron oxide orange, brown, and red; lamp black; titanium dioxide white; and Prussian Blue. They they use the pigments to make egg tempera paint and to create their own works of art.

Paint Pigments

Soap is a material known since ancient times. Fat from a roasting piece of meat mixing with the ashes of the fire made the earliest forms of soap. In this lab students use vegetable oil and sodium hydroxide, and a little magic with a co-solvent to make it easier to mix oil and water, to make their own soap.

Soap

Mirrors are nearly magical objects, even if one has not read the hundreds of stories involving magical mirrors. In this lab students make a mirrored test tube. It was written mainly for the opportunity for students to do a dramatic demonstration and to create a keepsake, though the text does give some background about the reactions involved. There is a historical connection, too, to organic chemistry and the detection of aldehydes from around the turn of the 20^th century.

Lab: Silver Mirror

Everybody likes ice cream. This is simply a fact. Strangely, it is not universally recognized that there should be an ice cream parlor, gelato shop, or frozen custard joint on every other street in a town. Fortunately, in Maine, one can take it for granted that ice cream can be had almost any time of the year at a pleasant and nearby business. Still, one can never really have too much ice cream and so why not make it in a chemistry lab?

Lab: Ice Cream

Demonstration Handouts

I have written several handouts for demonstrations that help students to comprehend what they're seeing and to apply what they see to the topics they are studying.

It is important for students to witness the reaction of sodium with water. Demonstrators are advised to use only very small pieces! Follow the demonstration with the old Alkali Metals video from the Open University.

Demonstration: Sodium Reacts with Water

The concept of the empirical formula can be hard to grasp at first. While a lab is the first choice for helping students to understand it, this demonstration can be done before a lab, or after, to aid student comprehension.

Demonstration: The Empirical Formula of Silver Oxide

Students can struggle to learn stoichiometry as they are not used to thinking in terms of ratios and direct proportions. Ratios in chemistry are particularly challenging because the basis of the simple whole-number ratios is the molecules, which no one can see. This demonstration attempts to help students see what's going on in a simple chemical change and to show them how stoichiometric calculations relate to measurements that can be made in the lab.

Stoichiometry Introduction

The concept of the limiting reactant is a simple one but when students can see it in action it makes a difference. This demonstration involves the use of baking soda and vinegar to inflate balloons. The size of the balloon helps to show the effects of the limiting reactant.

Limiting Reactant Demonstration

Students have not witnessed a lot of chemical reactions and this lack of familiarity is a barrier in their learning types of reactions and to their understanding of chemical equations. In this demonstration students see a single replacement reaction followed by a combustion/synthesis reaction.

Dancing Flames

This demonstration handout has little in the way of description of what students see but references the procedure to one of the Shakhashiri books. Students witness the production of hydrogen gas and the magical snuffing and re-lighting of a candle. Gases and stoichiometry are a focus.

Hydrogen Gas Preparation and Properties

The process of boiling is endothermic but because water is so hot when it boils, and most students are only familiar with water, students may assume it is exothermic. Exothermic changes are often associated with high temperature but endothermic changes may require a high temperature in order to occur. This demonstration attempts to help students see directly that boiling is endothermic.

Boiling Acetone at Reduced Pressure

The nature of boiling is confusing because most people do not appreciate that temperature is not the only factor involved. The air pressure above the liquid also plays a role since bubbles can’t form if their pressure is less than the air pressure. For a given pressure there is a specific temperature at which there is enough heat to vaporize a liquid in such a way that the vapor equals that given pressure. This demonstration helps students to see how pressure plays a role in boiling.

What does it Mean for a Liquid to Boil?

When materials dissolve to form a solution bonds are broken and bonds are formed. Often the strength and number of bonds formed is roughly equal so nothing dramatic happens when, for example, a salt is dissolved in water. Some salts, however, can release or absorb heat when they dissolve. In this demonstration students hold a small test tube with 1 g of anhydrous calcium chloride and feel the temperature rise (and watch it on a thermometer) as water is added.

Heat of Solution

Some properties of solutions depend only on the collection of particles, that is on the number of particles. These colligative properties include freezing point depression, which is when a solute causes the freezing point of a solution to be lower than the freezing point of a pure solvent.

Freezing Point Depression

This is a lesson I wrote for use with elementary school students on a special drop-in day.

Comparing Dry Ice and Water Ice

Exothermic reactions are exciting to witness and the dehydration of sugar by concentrated sulfuric acid is particularly dramatic. This demonstration allows students to practice concepts of thermochemistry including Hess's Law and stoichiometric calculations with enthalpy. It is also a memorable show.

Exothermic Dehydration of Sugar

Thermite is a favorite demonstration. Concepts of stoichiometry and thermochemistry are covered in this handout.

Thermite

Reaction rates are on the one hand easy to describe (they are how fast a reaction happens) and difficult to handle (the math can be labyrinthine). This simple demonstration is a chapter-opener for the study of chemical kinetics and covers the effects that solution concentration and particle size have on reaction rate.

Introduction to Reaction Rates

The calculations involved in finding the pH at different points in a titration are challenging for students. In order to know what kind of calculation to do they have to have a deep understanding of what’s going on at the molecular level. This demonstration gives students the task of finding the pH at different points in a titration and also underlines how an indicator is used.

Equilibrium with an Acid/Base Indicator

Entropy is one of the more difficult concepts in thermodynamics. Many people say it is just chaos or disorder and leave it at that. A more nuanced understanding of the concept is not out of reach. Entropy is simply a measure of the number of ways the atoms and molecules of a material can be arranged without changing things like volume, pressure, temperature, or other macroscopic variables. This demonstration uses a simulator and simple probability calculations to introduce students to entropy.

Entropy and Probability

Alchemy is a perennial favorite topic, though mostly we moderns misunderstand the ancients. Still, it's fun to play the sorcerer and to bring out your inner Hogwarts professor. This demonstration document is more for displaying behind the demonstrator during the magic, details for which read in the Shakhashiri book (vol. 4 of Demonstrations, demo 11.33). Light some candles and have students chant the magic words of the Latin names of the noble metals while you wait for the pennies to take on a silver appearance.

Demo: Copper to Silver to Gold