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Competency 043:
Chemical Properties of and Changes in Matter

Competency 043: Chemical Properties of and Changes in Matter

The teacher understands chemical properties of and changes in matter.

The atom is the basic unit of matter. This competency examines the structure of atoms and interactions among atoms, including the formation of chemical bonds. A chemical reaction, also called a chemical change, is a transformation of some substances into one or more other substances. The explosion of fireworks is an example of chemical changes. Chemical changes often can identified because they lead to color changes, the release or gain of energy, and production of an odor, other gases or solids. Chemical changes are not easily reversed.

For an introduction to chemistry, watch this video from Annenberg Learner on The World of Chemistry.


Structure and Components of the Atom

The beginning teacher describes the structure and components of the atom.

Key Concepts:

  • Atoms are composed of three types of particles: protons, neutrons, and electrons.
  • Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
  • Protons and neutrons reside in the nucleus of the atom and are responsible for most of the atomic mass.
  • Electrons reside in atomic orbitals around the nucleus. An atomic orbital is a mathematical calculation of the behavior of an electron or pair of electrons around the protons of an atom.
  • Electrons in their orbitals are arranged in shells. Each shell has one or more subshells. The electrons in the outermost shell, or valance electrons, tend to be responsible for the chemical behavior of an element.


Watch this short video from the television program, WKRP, for a humorous approach to learning the structure of the atom.

The Atom is explained in detail in this video from Annenberg Learning.

CHEM4KIDS offers a succinct explanation of atoms, the building blocks of matter.

Elements, Mixtures and Compounds, and their Properties

The beginning teacher distinguishes among elements, mixtures, and compounds and describes their properties.

Key Concepts:

  • A substance that contains only one kind of atom is an element. An element cannot be broken down into simpler substances (e.g., pure gold).
  • Elements combine to form chemical compounds. These compounds can either be ionic, (composed of positive and negative ions), or covalent (composed of neutral molecules that share bonds). Examples of compounds include the ionic compound, table salt (NaCl), and the covalent bond compound, water (H2O).
  • Mixtures consist of two or more elements or compounds that can be physically separated. A bucket containing sand and gold nuggets is an example of a mixture. The two substances are not joined together with bonds, but can be physically separated.


Review elements, compounds, and mixtures in this short description by the Department of Chemistry at Purdue University.

What is a Chemical Compound? is a brief video explanation from TutorVista.

Chemical Properties of an Element to its Placement in the Periodic Table

The beginning teacher relates chemical properties of an element to its placement in the periodic table.

Key Concepts:

  • The periodic table groups elements by similar properties.
  • Rows of elements are called periods. They are neighbors with different properties.
  • As you move from left to right in a period, the atomic size of the elements increases.
  • Columns of elements have similar chemical properties and are called groups or families.
  • The families on the left side of the periodic table are the metals while the families on the right side are non-metals.
  • As you move down in a family, the atomic size of the elements increases.
  • The last group on the far right in the periodic table is the noble gases. Atoms of noble gas elements have an outer electron shell that is complete (or full), which makes these elements less likely to form bonds with other elements (in other words, they are stable).
  • All elements “want” to be like the noble gases and have a complete or full outer shell of electrons. To do so, they must gain or lose electrons in their outer electron shell.
  • Metals tend to lose electrons, while the non-metals typically gain electrons to achieve stability.
  • The periodic table can be used to determine the valence electrons or number of electrons in the outer electron shell of an element.


The Periodic Table from Annenberg provides a comprehensive overview of atoms, electron shells and arrangement of the periodic table. Use the interactive games to test your knowledge.

This video from GPB Television describes how to use the periodic table, based on its organization.

For a quick review, consult the Periodic Table Study Guide from

Chemical Bonds and Chemical Formulas

The beginning teacher describes chemical bonds and chemical formulas.

Key Concepts:

  • Gaining or losing electrons in the outer shell of an atom is the basis for chemical bonds.
  • During covalent bonding the compounds share orbiting electrons in their outer shells to reach a more stable energy state.
  • A covalent bond is a strong bond between atoms that share one or more pairs of electrons in their outer shells to reach stability. They are “co-owners” of the electrons.
  • Some elements (non-metals) tend to strip other elements of their outer electrons to become stable. One example is chloride (Cl), which typically acquires an extra electron.
  • Some elements (metals) often give up their outer electrons to become stable. One example is sodium (Na).
  • An ion is an element that gains or loses electrons and thus takes on a negative or positive charge, respectively. A cation is a positively charged ion (such as Na+). An anion is a negatively charged ion (such as Cl-).
  • Positive and negative ions are attracted to each other resulting in the formation of weak ionic bonds. One example is the ionic bond formed by sodium and chloride (table salt).
  • The information in the periodic table is used to write chemical formulasThe following videos define and demonstrate ionic and covalent bonds in compounds.


Review atomic orbitals and electron shells in this section of the Interactive Periodic Table tutorial by Annenberg. Or watch this detailed video on Chemical Bonds also from Annenberg Learner.

Watch this animation to learn more about ionic and covalent bonds.

This video offers more information about Ionic and Molecular Compounds.

This video, Writing Formulas for Binary Ionic Compounds, shows the steps to determine the formula for ionic compounds.

Chemical Reactions and their Associated Equations

The beginning teacher analyzes chemical reactions and their associated chemical equations.

Key Concepts:

  • All chemical reactions can be represented by a chemical equation, which must balance.
  • A chemical reaction converts one or more substances into new substances with different physical and chemical properties. If magnesium (Mg) and hydrochloric acid are combined, a chemical reaction occurs resulting in magnesium chloride (MgCl2) and hydrogen gas (H2).
  • Chemical reactions break apart chemical bonds and form new ones.


The following videos describe the types of chemical reactions and how each can be defined by a chemical equation: Five Major Chemical Reactions

Chemical Reactions from the Discovery ChannelImportance of a Variety of Chemical Reactions that Occur in Daily Life

Follow these instructions from the well-known learning series “for Dummies,” to review how to balance a chemical equation.

Importance of a Variety of Chemical Reactions that Occur in Daily Life

The beginning teacher explains the importance of a variety of chemical reactions that occur in daily life (e.g., rusting, burning of fossil fuels, photosynthesis, cell respiration, chemical batteries, digestion of food).

Key Concepts:

  • Chemical reactions occur in all three phases of matter; solid, gas, and liquid.
  • Chemical reactions are required for the existence of life.
  • Chemical reactions may require energy or release energy.


Chemical reactions occur around, and in, us constantly. Read the following articles from to discover examples from everyday life: Chemical Reactions in Everyday Life and Chemical Change Examples.

Applications of Chemical Properties of Matter

The beginning teacher understands applications of chemical properties of matter in physical, life, and earth/space science and technology (e.g., materials science, biochemistry, transportation, medicine, and telecommunications).

Key Concepts:

  • Chemistry and the properties of matter are at the center of all new materials and discoveries in industry, medicine, and technology.
  • Materials science uses knowledge of chemical reactions to synthesize new materials with special properties and is one of the hottest career areas in science. Design and production touches practically every industry.
  • Biochemistry is the study of the chemical structures and reactions in living organisms. All living things use the same basic molecules, such as sugars, proteins and DNA, to live and grow.


The following article introduces materials science and applications in our world today: Materials Science from ACS Chemistry for Life

CHEM4KIDS offers a simple overview of biochemistry.

Applications of chemistry for the development of antibiotics and vaccines are described by the National Institutes of Health.

Fiorenzo Omenetto speaks about the unbelievable applications of silk in this TED talk. The chemical composition of silk is simple, but has multiple and varied applications for life.

HISD Project REACH U.S. Department of Education