It isn’t necessary to do complicated chemistry experiments in high school. Projects in this section use materials that are easy to obtain, but are definitely high school level chemistry experiments. Here are some helpful tips for downloading the printable projects.
Easy Chemistry Project: Conductivity and Exploring Solutions
This lab will explore the solubility of three solutes, as well as the electrical conductivity of three solutions. Prior to doing your lab, remember that water is a polar molecule, while xylene is a non-polar molecule. Some molecular compounds with polar, covalent bonds will dissolve when they are dissolved by polar molecules.
A non-polar molecule, however, will dissolve a non-polar molecule whose covalent bonds are non-polar. In contrast, alcohol dissolves substances in a variety of ways. “Intermediate polarity” is said to describe it.
This project requires you to know and understand the following terms:
- The term ‘soluble’ refers to a substance that can dissolve in a particular substance. Its solubility makes it capable of doing so. Salt, for instance, is soluble in water. Insoluble oil cannot be dissolved in water.
- A solute is a substance that is being dissolved.
- Water is a solvent (the substance in which something is dissolved).
- A polar molecule has both a slight negative and positive charge at each end of its structure. Molecules such as water are polar.
- An asymmetrically arranged nonpolar molecule has neither a positive nor a negative charge.
Click here to print the following lab, and follow the directions carefully. Keep a lab notebook where you can record all of your observations.
Thinking About the Lab
As you reflect on your lab experience, consider the following questions:
- Using your lab results, make a short list of what each solvent might be able to clean.
- Take Windex, for example, as an example of a common household cleaner. What are the benefits of using an alcohol-based window cleaner?
- Cooking sprays with non-stick properties are often used by bakers. Why do they do this?
- For the types of tasks that hydraulic fluid performs, what makes it superior to water? (Hydraulic fluid is used in hydraulic breaks and in systems that move heavy objects.)
Moderate Project: Lowering the Freezing Point of Water (Ice Cream Chemistry)
The freezing point of water has probably already been lowered before. If you’ve ever seen trucks spread salt before a winter storm, you’ve seen chemistry in action. By lowering the freezing point of water, salt makes roads safer and raises the temperature at which it freezes.
In this project, you will calculate the molality and test the freezing point of three beakers of salt/water solution and three beakers of sucrose/water solution. Next, you’ll determine how the solute affects the freezing point depression of the solution.
In order for a solution’s freezing point to be lowered, three factors must be taken into account:
- Molality (m) refers to the amount of solute per kilogram of solvent in a solution
- In the case of sugar, the van’t Hoff factor (i) is 1, and in the case of salt, the van’t Hoff factor is 2.
- The molal freezing-point-depression constant of the solvent; for water this is Kf = 1.86° C/m where Kf = the freezing point depression constant
To predict how much a solute’s freezing point will be lowered by adding a given solvent, you can use the equation: ΔT = (Kf)(m)(i) where:
- ΔT is the freezing point depression in degrees Celsius (° C)
- Kf is the molal freezing-point-depression constant in degrees Celsius per molal (° C/m)
- m is the molality of the solution in moles per kilogram (mol/kg)
- i is the van’t Hoff factor of the solute, which does not have units
The lab procedure can be printed by clicking here. Take careful notes in your lab notebook and follow the directions exactly. Write down the freezing point of each of your solutions, including the beaker of plain water, which is the control solution in this lab.
Finding the Expected Freezing Point Depression
- For each solution, determine how many moles of solute are present. As a general rule, moles are defined as the weight of the substance (in g) divided by the gram molecular weight of the substance. Salt has a molecular weight of 58.443 grams, and sucrose has a molecular weight of 342.3 grams. Molecular weight of 100mL of water is .1kg.
- Calculate the molecular weight of the solute per kilogram of solvent, which is the molality.
- Comparing the molalities of salt/water solutions and sucrose/water solutions.
- Calculate the freezing point depression using the formula above for ΔT. How does your calculation compare with what you observed? Is there a causal relationship between the molality of a solution and its freezing point depression?
Advanced Project: Hot Ice (Sodium Acetate)
The sodium acetate (one of the products of baking soda and vinegar mixture) has the unique property of freezing without actually freezing. As a matter of fact, this substance becomes hotter rather than cooler when it freezes.
The wow factor can be achieved by using hot ice. In order to do it right, however, there is a certain amount of finesse involved. You may have to try it several times before it works.
Hot ice (freezing sodium acetate) is an exothermic reaction – meaning that as the sodium acetate ‘freezes’ the substance gives off heat. In fact, it is the same type of chemical reaction used in MREs, hand warmers and similar products. Sodium acetate is one of the by-products of baking soda and vinegar. The formula for the reaction is as follows: Na+[HCO3]- + CH3-COOH → CH3-COO- Na+ + H2O + CO2.
Click to print the lab procedure to the right. While making hot ice is relatively safe (the chemical itself is non-toxic), caution should be used whenever you are handling hot substances. Make sure to note the temperatures of the sodium acetate as you move through the experiment.
Things to Notice and Do With Hot Ice
The important thing to notice is the supercooled liquid (liquid that is cooled below its melting point), and the exothermic reaction that you get when you reintroduce a crystal to the solution. The crystal acts as a nucleation site. You can make hot ice sculptures by introducing a crystal as you pour. When you do this, what is the temperature of the hot ice?
Click to print this project.
Remember that when you’re working with chemicals, even ones that you think are safe, you should always use safety goggles, and perhaps protective gloves. It’s important to get into the habit of using safety equipment so that it is automatic.
Remember as well, that when you are working over a stove, you should always wear oven mitts or use tongs. Common sense in the lab goes a long way toward an enjoyable experience.