Matter and Its Classification

Definition and States of Matter

Matter is defined as anything that has mass and occupies space. It exists in three primary states: solid, liquid, and gas. Each state has distinct physical properties.

• Solid: Definite shape and volume; particles are closely packed.

• Liquid: Definite volume but no definite shape; particles are less tightly packed and can flow.

• Gas: No definite shape or volume; particles are far apart and move freely.

• Example: Water exists as ice (solid), liquid water, and steam (gas).

Pure Substances and Mixtures

A pure substance has a fixed composition and distinct properties. Pure substances are classified as elements or compounds.

• Element: A substance that cannot be broken down by chemical means. Examples: Hydrogen (H), Oxygen (O).

• Compound: Two or more elements chemically combined in a fixed ratio. Examples: Water (H2O), Carbon Dioxide (CO2).

• Mixture: Combination of two or more substances that retain their individual properties. (Additional info: Mixtures can be homogeneous or heterogeneous.)

Atomic Structure and the Periodic Table

Atoms and Subatomic Particles

Atoms are the basic units of matter, composed of three main subatomic particles:

• Protons: Positively charged particles located in the nucleus.

• Neutrons: Neutral particles also found in the nucleus.

• Electrons: Negatively charged particles that orbit the nucleus.

• Example: A carbon atom has 6 protons, 6 neutrons, and 6 electrons.

The Periodic Table

The periodic table organizes elements by their atomic number (number of protons). It provides information about element properties and relationships.

• Atomic Number: Number of protons in an atom; determines the element's identity.

• Example: Oxygen has atomic number 8.

Chemical Bonds

Ionic and Covalent Bonds

Chemical bonds are forces that hold atoms together in compounds. The two main types are ionic and covalent bonds.

• Ionic Bond: Formed when electrons are transferred from a metal to a nonmetal, creating ions with opposite charges that attract each other.

• Covalent Bond: Formed when atoms share pairs of electrons.

• Example: Sodium chloride (NaCl) is an ionic compound; water (H2O) is a covalent compound.

Measurement and Units

SI Units

The International System of Units (SI) is used for scientific measurements. The main SI units are:

• Meter (m): Length

• Kilogram (kg): Mass

• Second (s): Time

• Kelvin (K): Temperature

• Mole (mol): Amount of substance

Significant Figures

Significant figures indicate the precision of a measurement. The number of significant digits reflects the certainty in the measured value.

• Rule: All nonzero digits are significant; zeros between nonzero digits are significant; leading zeros are not significant; trailing zeros in a decimal are significant.

• Example: 0.00450 has three significant figures.

Density

Density is a physical property defined as mass per unit volume. It is used to identify substances and predict behavior in mixtures.

• Formula:

• Where: d = density, m = mass, V = volume

• Example: If a sample has a mass of 10 g and a volume of 2 mL, its density is