Science Chapter 2: Atoms and Molecules

Everything that occupies space and has mass. It can be in different states such as solid, liquid, and gas, and is made up of atoms.

The amount of space a substance occupies.

The amount of matter in an object. It is a fundamental property and remains constant regardless of the state of matter.

The ratio of mass per unit volume. It determines how compact a substance is.

The smallest constituent of an element, characterized by a specific number of protons, neutrons, and electrons. Each element is made up of the same type of atom.

The central core of an atom, containing protons and neutrons. It holds almost all the atom's mass.

A subatomic particle found in the nucleus, with a positive electric charge. The number of protons determines the element's identity.

A subatomic particle found in the nucleus, with no charge. The number of neutrons affects the atom's mass (isotopes).

The center of an atom, containing protons and neutrons.

A negatively charged particle that orbits the nucleus of an atom.

A substance made up of only one type of atom.

A table that organizes all known elements based on their properties and atomic number.

The number of protons in an atom's nucleus.

The number of protons in an atom always equals the number of electrons.

The outer shell of electrons determines some of an element's electrical properties.

Atoms of the same element that have the same number of protons but different numbers of neutrons. They have the same atomic number but different atomic masses.

The smallest unit of an element or compound that can exist independently and still retain the chemical properties of that substance.

A substance formed when two or more different elements chemically combine in a fixed ratio.

The mass of an atom is primarily determined by the number of protons and neutrons in its nucleus, with electrons' mass being negligible.

A neutral atom has an equal number of protons and electrons, resulting in a balanced charge.

When an atom gains electrons, it becomes negatively charged, forming an anion.

When an atom loses electrons, it becomes positively charged, forming a cation.

A molecule containing only one type of atom. Example: O2 (Oxygen gas).

A molecule containing atoms of different elements. Example: H2O (Water).

The process by which atoms share or transfer electrons to form bonds.

A combination of two or more substances where each substance retains its individual properties. Example: saltwater.

The ratio of elements in a mixture is not fixed.

A mixture where the components are evenly distributed.

A mixture where the components are not evenly distributed.

The state of matter where substances have a fixed shape and volume. Their molecules are tightly packed together, allowing minimal movement.

The state of matter where substances have a fixed volume but can change shape. Their molecules are closer together than in gases, but they can move around more freely.

The state of matter where substances have no fixed shape or volume. Their molecules are far apart and move around freely.

The process where a substance changes from solid to liquid. It happens when heat energy is absorbed by the molecules, causing them to move more freely.

The process where a substance changes from liquid to gas. It happens when heat energy is absorbed by the molecules, causing them to break free from the liquid's surface.

The force of attraction between molecules. These forces hold substances together in various states of matter.

The physical state of a substance does not affect its chemical composition. Ice, water, and steam are all H2O, just in different states.

Molecules in solids are closely bound together, restricting their movement compared to liquids or gases. Gases flow more easily because their molecules have weaker attractive forces and higher energy levels.

The three states of matter are solid, liquid, and gas. Solids have a fixed shape and volume, liquids have a fixed volume but not a fixed shape, and gases have neither a fixed shape nor a fixed volume.

Solids are generally more dense than liquids, but there are exceptions like cork and balsa wood. Gases are the least dense state of matter.

Solids expand and contract with temperature changes, but not as much as liquids or gases. Gases expand and contract most dramatically with temperature and pressure changes.

The chemical elements are the fundamental building blocks of matter. Each element is made up of a unique type of atom.

Atoms are the smallest unit of an element and consist of a nucleus containing protons and neutrons, surrounded by electrons orbiting in shells.

A chemical compound is formed when two or more different elements combine chemically in a fixed ratio. Examples include water (H2O), carbon dioxide (CO2), and sodium chloride (NaCl).