Matter

Unit Review Sheet

Facts and Definitions

Lesson 1: Elements and the Periodic Table

• Matter is anything that has mass and takes up space.
• An atom is the smallest particle of an element.
• An element is the simplest type of a substance. It is a substance whose atoms are all the same.
• A substance made of two or more elements is called a compound.
• Elements are arranged by their properties into a chart called the periodic table of the elements.
• Dmitri Mendeleev, a Russian scientist, created the periodic table in 1869. Many elements had not yet been discovered, but he knew where new elements would go based on the properties of the known elements.

Lesson 2: Introduction to Metals

• Metals are elements whose atoms tend to line up and stick closely together. Many metals have luster (after they have been processed and cleaned), are malleable, and are good conductors of heat and electricity.
• If a material is shiny, can reflect light, and be polished, it has the quality of luster.
• If a material can be shaped or formed without breaking, it is described as being malleable. A material that is not malleable is described as brittle.
• There are 6 categories of metals — the familiar transition metals and main-group metals; the less-familiar alkali metals, alkaline earth metals, and lanthanides; and the man-made and short-lived actinides.

Lesson 3: Introduction to Metalloids

• Radioactive means an element decays into a different element and emits dangerous energy as it decays.
• Many metalloids are semiconductors that either conduct a small amount of electricity or conduct electricity only under certain conditions. This makes them ideal for many electronic devices like computers and cellular phones. Scientists use these special properties to build the technology we use every day.

Lesson 4: Introduction to Nonmetals

• There are 3 types of nonmetals, classified into halogens, noble gases, and other nonmetals. Halogens are elements that react easily with other elements, and noble gases are gases that rarely react with other elements.
• Nonmetals includes elements that are most found in living things, including carbon, nitrogen, oxygen, phosphorus, and sulfur.

Lesson 5: Classifying as Solids, Liquids, or Gases

• Most metals and metalloids are solid at room temperature.
• Only two elements are liquids at room temperature: the metal mercury and the nonmetal bromine.
• The only elements that are gases at room temperature are hydrogen, nitrogen, oxygen, fluorine, chlorine, helium, neon, argon, krypton, xenon, and radon. All are nonmetals.
• Colloids are substances with tiny particles of one substance dispersed in another substance. For example, shaving cream has air and liquid mixed together, and milk has tiny droplets of fat interspersed evenly throughout the water.

Lesson 6: Classifying by Density

• Mass is the amount of matter in a substance (whereas weight measures how heavy a substance is due to the pull of gravity on it)
• Volume is how much space something takes up
• Density is how much matter there is in a certain space, or mass divided by volume. It describes how closely the molecules in a substance are pressed together.

Lesson 7: Classifying by Magnetic Properties

• Only three elements are naturally magnetic at room temperature, and they are all metals: iron, nickel, and cobalt.
• Ferromagnetic describes an element or compound that is strongly magnetic, such as iron.
• Paramagnetic describes an element or compound that can be weakly magnetic, such as aluminum.
• Diamagnetic describes an element or compound that pushes away from magnetic forces, such as bismuth.

Lesson 8: Classifying by Conductivity

• Conductivity means the ability to transmit energy as heat, electricity, or sound.
• An insulator is a material that does not transmit energy well.
• Semiconductors conduct a small amount of electricity.
• Superconductors like yttrium continue to transmit electricity even after the power is turned off.

Lesson 9: Classifying by Water Solubility

• Solubility means the ability to dissolve.
• Elements and compounds can be water-soluble, meaning they dissolve in water, or fat-soluble, meaning they dissolve in oils or fats.
• Hard water is water with many dissolved minerals in it.

Final Project: Mystery Elements

• [none]