Return to : Science Newsletter

The Structure of Matter

Each of the more than 100 elements of matter has distinct properties and a distinct atomic structure. All forms of matter are composed of one or more of the elements. As a basis for understanding this concept students should know :

  • the structure of the atom and how it is composed of protons, neutrons, and electrons.
  • compounds are formed by combining two or more different elements and that compounds have properties that are different from their constituent elements.
  • atoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long-chain polymers.
  • the states of matter (solid, liquid, gas) depend on molecular motion.
  • in solids the atoms are closely locked in position and can only vibrate; in liquids the atoms and molecules are more loosely connected and can collide with and move past one another; and in gases the atoms and molecules are free to move independently, colliding frequently.
  • how to use the periodic table to identify elements in simple compounds.

The Periodic Table

The organization of the periodic table is based on the properties of the elements and reflects the structure of atoms. As a basis for understanding this concept students know:

  • how to identify regions corresponding to metals, nonmetals, and inert gases.
  • each element has a specific number of protons in the nucleus (the atomic number) and each isotope of the element has a different but specific number of neutrons in the nucleus.
  • substances can be classified by their properties, including their melting temperature, density, hardness, and thermal and electrical conductivity.

Chemical Reactions

Chemical reactions are processes in which atoms are rearranged into different combinations of molecules. As a basis for understanding this concept students know:

  • reactant atoms and molecules interact to form products with different chemical properties.
  • the idea of atoms explains the conservation of matter: in chemical reactions the number of atoms stays the same no matter how they are arranged, so their total mass stays the same.
  • chemical reactions usually liberate heat or absorb heat.
  • physical processes include freezing and boiling in which a material changes form with no chemical reaction.
  • how to determine whether a solution is acidic, basic or neutral.

The Chemistry of Living Things

Principles of chemistry underlie the functioning of biological systems. As a basis for understanding this concept students know:

  • that carbon, because of its ability to combine in many ways with itself and other elements, has a central role in the chemistry of living organism.
  • that living organisms are made of molecules consisting largely of carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur.
  • that living organisms have many different kinds of molecules including small ones, such as water and salt, and very large ones, such as carbohydrates, fats, proteins, and DNA.

Back to Top