The Scientific Method in Chemistry

Chemistry relies on observation and experimentation to formulate hypotheses, proposing tentative explanations for observations.
Scientific laws summarize extensive experimental observations, describing or predicting aspects of the natural world.
A theory is a well-substantiated, comprehensive, and testable explanation of particular natural phenomena.

The macroscopic domain includes everyday objects that can be directly sensed by sight or touch.
The microscopic domain refers to the realm of very small entities, often visualized through microscopes.
The symbolic domain encompasses the specialized language, including chemical symbols, that represents both macroscopic and microscopic entities.

Matter is defined as anything that occupies space and has mass.
Common states of matter include:
- Solid: Rigid with a definite shape.
- Liquid: Flows and conforms to the shape of its container.
- Gas: Adapts to both the shape and volume of its container.
Plasma: A gaseous state with significant electrically charged particles, found naturally in stars and lightning, and artificially in devices like television screens.

Mass quantifies the amount of matter in an object; weight is the force of gravity acting on that mass. Mass remains constant regardless of location, while weight varies.
The Law of Conservation of Matter states that the total quantity of matter remains unchanged during chemical and physical transformations.

Element: A pure substance that cannot be decomposed chemically into simpler substances.
Pure Substances: Exhibit constant composition and include:
- Elements: Composed of one type of atom.
- Compounds: Formed from two or more types of elements, can be broken down chemically (e.g., H2O, C6H12O6).
Mixture: Composed of two or more types of matter that can be physically separated, existing in varying amounts.
- Homogeneous Mixture: Uniform composition throughout, also known as a solution.
- Heterogeneous Mixture: Composition varies from one part to another.

Atom: The smallest particle of an element retaining the element's properties and capable of chemical bonding.
Molecule: A group of two or more atoms bonded together through chemical forces.

Physical Property: Characteristics not associated with changes in chemical composition, such as density, color, hardness, and boiling/melting points.
Physical Change: A change in the state or properties of matter without altering its chemical composition.
Chemical Property: Describes a substance's potential to undergo a chemical change (e.g., flammability, reactivity).

Extensive Properties: Depend on the quantity of matter present (e.g., mass, volume).
Intensive Properties: Independent of the quantity of matter (e.g., density, temperature).

Measurements are critical for forming hypotheses and theories in chemistry and provide:
- Size or magnitude (number).
- Standard of comparison (unit).
- Indication of uncertainty.
The International System of Units (SI) is the updated metric system used in chemistry since 1964, with key units including:
- Length: meter (m)
- Mass: kilogram (kg)
- Time: second (s)
- Temperature: kelvin (K)
- Electric Current: ampere (A)
- Amount of Substance: mole (mol)
- Luminous Intensity: candela (cd)