Science Chapter: Matter and Atomic Structure

A general term used to describe all substances that occupy space and have mass.

The amount of space a substance occupies.

The amount of matter in a substance.

The measure of mass per unit volume.

The smallest constituent of ELEMENTS, the simplest form of matter. They are composed of a nucleus and electrons.

The central part of an atom, containing protons and neutrons.

Positively charged particles found in the nucleus of an atom.

Neutral particles found in the nucleus of an atom.

A pure substance composed of only one type of atom.

The arrangement of known elements in order of increasing atomic number.

The number of protons in an atom's nucleus, which determines its identity.

The outermost shell of an atom, which determines its chemical properties.

Concentric layers around the nucleus of an atom, where electrons reside.

An atom with either a positive or negative charge due to losing or gaining electrons.

Atoms of the same element with different numbers of neutrons. Their atomic number remains the same, but their atomic mass changes.

Two or more atoms chemically bonded together.

A substance made up of two or more different elements chemically combined in a fixed ratio.

The process of atoms combining chemically with other atoms.

The mass of an atom is primarily due to the mass of the protons and neutrons, as the mass of electrons is insignificant.

The atomic mass unit (amu) is a standard unit of mass used for atomic and molecular masses. 1 amu is approximately equal to 1.66 x 10^-27 kg.

The number of protons in an atom's nucleus. It determines the element.

The number of atoms of each element in a molecule is represented by subscripts. For example, H2O indicates two hydrogen atoms and one oxygen atom in a water molecule.

A mixture consists of two or more substances that are physically combined, meaning they are not chemically bonded. Each substance retains its own properties.

A mixture can have varying ratios of its components. For example, salty water can be made with different amounts of salt.

Metal alloys are mixtures of different metals that are combined to create materials with improved properties. For example, adding carbon to iron makes it stronger and harder.

Molecules are always in motion, vibrating and moving around. The speed and distance of this movement depends on the temperature.

Temperature is directly related to molecular activity. The hotter the temperature, the faster the molecules move.

The state of matter (solid, liquid, or gas) influences the speed and distance of molecular movement. Molecules in gases are much more spread out and move faster than in solids.

A state of matter where the molecules are closely packed together, with strong intermolecular forces, resulting in a fixed shape and volume.

A state of matter where the molecules are less tightly packed than solids, allowing them to move more freely. They have a fixed volume but take the shape of their container.

The process where a solid transforms into a liquid due to increased heat energy, causing molecules to break their fixed positions and move more freely.

The process where a liquid transforms into a gas due to increased heat energy, causing molecules to break their intermolecular forces and move independently.

The force of attraction between molecules of a substance, which determines the physical state of matter.

The energy possessed by molecules due to their movement, which influences their state of matter. Higher kinetic energy leads to more movement and weaker intermolecular forces.

The process by which a gas transforms into a liquid due to a decrease in temperature or an increase in pressure.

The density of a substance is determined by the mass of its atoms and how closely its molecules are packed.

Solids are generally denser than liquids, but there are exceptions like cork and balsa wood.

Gases are the least dense state of matter due to their molecules being spread out far apart.

Solids are less compressible because their molecules are tightly packed, making it harder to reduce their volume. Liquids are more compressible than solids, but still less than gases. Gases are highly compressible because their molecules are far apart.

Changing the temperature of a substance can alter its state of matter. Increasing temperature typically causes a solid to melt into a liquid and then vaporize into a gas.

Solids expand with increasing temperature because their molecules vibrate more vigorously, occupying more space. Liquids and gases also expand but more readily.

Gases are highly compressible because their molecules have large gaps between them, allowing them to be squeezed together like a compressed spring.

Liquids and gases expand or contract more readily than solids when their temperatures change. This is because their molecules have more freedom to move.