Sample Topics for Classroom Use

Chemistry Passages

"Every substance has a unique set of properties, or characteristics, that allow us to recognize it and to distinguish it from other substances. Properties of matter can be grouped into two categories: physical and chemical. Physical properties are those properties that we can measure without changing the basic identity of the substance. Physical properties include color, hardness, density, melting point, and boiling point. Chemical properties describe the way a substance may change or 'react' to form other substances. A common chemical property of iron is its ability to combine with oxygen in the presence of water to form a red-brown substance that we call rust (an oxide of iron)."

--Brown and LeMay 1988

"Matter can undergo changes of two basic types: physical changes and chemical changes. Physical changes are processes in which a material changes its physical appearance but not its basic identity. The evaporation of water is a physical change. When water evaporates, it changes from the liquid state to the gas state, but it is still water; it has not changed into any other substance. All changes of state are physical changes. In chemical changes, also called chemical reactions, substances change not only in physical appearance but also in basic identity; that is, one substance is converted into another. For example, hydrogen burning in air undergoes a chemical change in which it is converted to water."

Brown and LeMay 1988

Chemistry Questions

1.	I don't get the difference between a reactant and a reagent. Could you explain it again?
2.	How can you separate substances when their boiling points are less than 30 degrees apart?
3.	When I buy shampoo in the store sometimes I see a pH value on the bottle. Could you go over again what pH value is and explain how people can choose which pH value is best for their hair?
4.	I'd like to know what the phase rule is and how it's used to figure out the number of degrees of freedom.
5.	I don't really understand why human blood is a buffer solution.

General Interest Topics

1.	Why salt causes snow to melt and cars to rust.
2.	Why acid rain is such a danger to living creatures in lakes and rivers.
3.	Some people think hot water freezes faster than cold water. Is this true? Why or why not?
4.	Why ethyl alcohol is drinkable and methyl alcohol is poisonous.

Chemistry Problem

Sample Problem: Calculate the molarity of a solution made by dissolving 23.4 g of sodium sulfate (Na₂SO₄) in enough water to form 125 mL of solution.

Solution to Sample Problem: (Kristin, need to recreate equation)

Problem: Calculate the molarity of a solution made by dissolving 5.00 g of C₆H₁₂O₆ (MW = 180 amu) in sufficient water to form 100 mL of solution.

--Brown and LeMay 1988