Lesson 7: Classifying Matter
Getting Started
In this lesson, you will look more closely at chemistry, the branch of science dealing with the structure, composition, properties, and reactive characteristics of substances, especially at the atomic and molecular levels. In this lesson you will be challenged to look at matter based on how it is used and where it occurs. You will also take into consideration differences based on whether an object is composed of simple elements in a pure form, compounds, or mixtures.
Remember from previous lessons that an element is the simplest form of matter in its pure form. Compounds are substances formed by the chemical combination of elements in fixed proportions (unchanging quantities). Compounds are pure chemical substances that can be separated into simpler substances by chemical reactions. Mixtures are a combination of two or more substances that are not chemically united and do not necessarily exist in fixed proportions to each other. The difference between a compound and a mixture is subtle, and in this lesson, we will look more closely at how the atoms that make up compounds and mixtures are packed together. We will also take your developing understanding of chemistry and use it to look at the variety of ways that elements, compounds, and mixtures make up all living and nonliving substances.
Remember from previous lessons that an element is the simplest form of matter in its pure form. Compounds are substances formed by the chemical combination of elements in fixed proportions (unchanging quantities). Compounds are pure chemical substances that can be separated into simpler substances by chemical reactions. Mixtures are a combination of two or more substances that are not chemically united and do not necessarily exist in fixed proportions to each other. The difference between a compound and a mixture is subtle, and in this lesson, we will look more closely at how the atoms that make up compounds and mixtures are packed together. We will also take your developing understanding of chemistry and use it to look at the variety of ways that elements, compounds, and mixtures make up all living and nonliving substances.
Stuff You Need
- Eyewitness Chemistry by Ann Newmark
- measuring cups
- oven mitt or potholder
- safety goggles (kit)
- salt
- small cups (kit)
- sugar
- tablespoon
- tea light candle (kit)
- test tube clamp (kit)
- test tube holder (kit)
- test tubes (kit)
Ideas to Think About
- What makes one piece of matter different from another?
- What patterns can be observed in elements?
Things to Know
- compounds: substances formed by the chemical combination of elements in fixed proportions; pure chemical compounds can be separated into simpler substances by chemical reactions
- chemistry: a branch of science dealing with the structure, composition, properties, and reactive characteristics of substances, especially at the atomic and molecular levels
- fixed proportions: unchanging quantities of each element that is part of a compound
- mixtures: a combination of two or more substances that are not chemically united and do not exist in fixed proportions to each other
Skills
- Classify matter as elements, compounds, or mixtures based on how the atoms are packed together in arrangements. (S)
- Evaluate evidence that elements combine in a multitude of ways to produce compounds that account for all living and nonliving substances. (S)
Introducing the Lesson
In this lesson, your child will receive a basic introduction to some ideas associated with chemistry, including understanding how compounds and mixtures differ at the atomic and/or molecular level. Hopefully, your child will gain a new awareness of how the world is held together and the subtle complexity that surrounds him whatever the environment.
Materials: Eyewitness Chemistry by Ann Newmark
Read p. 6, pp. 14-15, and pp. 20-21 in Eyewitness Chemistry. (Optionally, read pp. 7-11.) Then answer the following questions.
Questions
- What is the difference between a mixture and a compound?A mixture is a substance containing different kinds of molecules that can be physically separated from one another. A compound is a substance that contains more than one type of atom — in a compound the atoms are bound together chemically. They cannot be physically separated from one another.
- Name 3 ways that the substances in a mixture can be separated.Answers could include the separatory (glass flask used to separate liquids that do not mix), filtering, evaporation, chromatography, or fractional distillation.
- What does it mean if an element is unreactive? Give an example of an unreactive element.Unreactive elements don't react with other elements and don't easily form compounds. The noble gases (helium, neon, argon, krypton, xenon, or radon) are unreactive elements.