States of Matter: Solids, Liquids, and Gases

Particle Nature of Matter

• Matter is anything that occupies space and has weight.
• Properties are characteristics that describe a material sample.
• Mass measures the amount of matter in an object.
• Volume measures the space an object takes up.
• Solids have definite shapes and volumes because their particles are tightly packed and vibrate in place.
• Liquids are close together and move, which causes them to take the shape of their container.
• Gases take the shape of their container.

Particle Model of Matter

• In gases, particles move randomly at high speed and travel in straight lines.

Density

• Density describes how much space an object or substance takes up, or the amount of mass per unit volume.

Physical Changes of Matter

• Physical change results in no new materials forming.
• Substances can change their physical phase when conditions are altered.
• Temperature affects matter phase transitions.
• Evaporation processes involve molecules escaping into a gas phase.
• Condensation involves a substance changing from a gas to liquid phase.
• Melting transforms a solid into a liquid.
• Freezing changes a liquid into a solid.
• Sublimation is when a solid turns directly into a gas.
• Deposition is when gas turns directly into a solid.
• Vapor results when molecules escape a liquid into a gaseous phase.

The Subatomic Particles

• Atoms consist of neutrons, electrons, and protons.
• Neutrons are neutral.
• Electrons have a negative charge.
• Protons have a positive charge.
• The nucleus contains protons and neutrons.
• The outer region holds electrons.
• Atoms contain positive and negative charges.
• Protons and neutrons are also known as nucleons.
• Atomic number gives the number of protons in an atom.
• Mass number is the combined number of protons and neutrons.
• Isotopes are atoms of an element with the same atomic number but different mass numbers.
• Ions are atoms with extra or missing electrons.

Johann Wolfgang Döbereiner

• In 1817, he grouped chemical elements into triads based on similar properties.

John Newlands

• In 1863, he proposed the Law of Octaves, noting that after every seven elements, their properties repeat.

Lothar Meyer and Dmitri Mendeleev

• In 1869, they both independently developed periodic tables.

Henry Moseley

• In 1913, he used X-ray spectral lines for accurate atomic numbers, helping rearrange the periodic table.

Periodic Table Arrangement

• Period is a horizontal row.
• Group or family is a vertical column.
• Metalloids are elements with properties of both metals and nonmetals.
• Alkali metals, Alkaline Earth metals, and Halogens are groups of elements located in the periodic table.

Properties of Elements in the Periodic Table

• F, Cl, Br, I, and At are halogens.
• Noble gases include He, Ne, Ar, Kr, Xe, and Rn.
• Atomic radii indicate the size of an atom.
• Ionization energy is the energy needed to remove an electron from an atom.
• Electronegativity describes the ability of an atom to attract electrons.
• Electron affinity is the tendency of an atom to gain electrons.
• Metallic character decreases as you move from left to right across a period in the periodic table.