Matter and Energy: States, Properties, and Changes in GOB Chemistry

States of Matter

Classification and Properties

All matter in the universe can be classified into one of three states: solid, liquid, or gas. Each state has distinct physical properties that determine its behavior and appearance.

• Solid: Has a definite fixed shape and volume. Particles are closely packed in a regular, fixed geometric pattern and move very little. Solids exhibit low compressibility.

• Liquid: Has a definite volume but no fixed shape; takes the shape of its container. Particles move more independently than in solids but are still close together. Liquids exert pressure on the walls of their container and have low compressibility.

• Gas: Has neither definite shape nor volume; expands to fill its container. Particles move independently and rapidly, are far apart, and exhibit high compressibility.

Example: Water exists as ice (solid), liquid water, and water vapor (gas) depending on temperature and pressure.

Physical and Chemical Properties and Changes

Definitions and Identification

Properties and changes of substances are classified as either physical or chemical:

• Physical Property: A characteristic that can be observed or measured without changing the substance's identity (e.g., melting point, color, density).

• Chemical Property: A characteristic that describes a substance's ability to undergo a specific chemical change (e.g., reactivity with acid, flammability).

• Physical Change: A change that affects the form of a chemical substance, but not its chemical composition (e.g., melting, boiling).

• Chemical Change: A change that results in the formation of new chemical substances (e.g., burning, rusting).

Examples:

• Melting ice is a physical change because the chemical identity of water remains the same.

• Burning coal is a chemical change because new substances are formed.

• Potassium is a chemical property because it is among the most reactive elements.

• Sodium added to water produces hydrogen gas and a water solution of sodium hydroxide, which is a chemical change.

Mixtures: Homogeneous and Heterogeneous

Classification of Mixtures

Mixtures can be classified as homogeneous (uniform composition throughout) or heterogeneous (non-uniform composition).

• Homogeneous Mixture (Solution): Components are evenly distributed; appears as a single phase. Example: salt water, air.

• Heterogeneous Mixture: Components are not evenly distributed; different phases are visible. Example: salad, oil and water.

Example: Sparkling wine is homogeneous, while well-stirred sugar water is also homogeneous. Soil and hamburger are heterogeneous.

Energy Changes in Physical and Chemical Processes

Types of Energy and Energy Transformations

Energy is involved in all physical and chemical changes. The two main types of energy are potential energy (P) and kinetic energy (K).

• Potential Energy (P): Stored energy due to position or composition.

• Kinetic Energy (K): Energy of motion.

Energy changes can be classified as endothermic (energy absorbed) or exothermic (energy released).

• Endothermic Process: Absorbs energy from surroundings (e.g., melting ice).

• Exothermic Process: Releases energy to surroundings (e.g., burning fuel).

Example: When you make coffee, heating water is an endothermic process; letting the mixture cool is exothermic as heat is released to the environment.

Table: States of Matter and Their Properties

Description	State of Matter
Has a definite fixed shape	Solid
Particles flow over each other, while retaining a fixed volume	Liquid
Exerts pressure on all walls of the container	Gas
Exhibits high compressibility	Gas
Particles move independently of each other	Gas
Particles arranged in a regular, fixed geometric pattern	Solid
Exhibits high compressibility	Gas

Table: Physical vs. Chemical Properties and Changes

Statement	Type
Potassium is a solid at room temperature	Physical property
Potassium is among the most reactive elements	Chemical property
Melts ice	Physical change
Steam rises at 90°C	Physical change
Burning coal	Chemical change
Discarding garbage	Physical change
Sodium added to water produces hydrogen gas and a water solution of sodium hydroxide	Chemical change
Melting an ice cube	Physical change
Potassium conducts electricity	Physical property
Alkali metals form salts with many other elements	Chemical property
Sodium has a metallic luster	Physical property

Additional Info

• Formula for Kinetic Energy: $KE = \frac{1}{2}mv^2$

• Formula for Potential Energy (gravitational): $PE = mgh$

• Phase Changes: Melting, freezing, boiling, condensation, sublimation, and deposition are all physical changes.

• Mixtures: Homogeneous mixtures are also called solutions; heterogeneous mixtures have visibly different components.