Matter and Its Properties

Definition and Classification of Matter

Matter is anything that has mass and occupies space. It can be classified based on its physical and chemical properties, as well as its composition.

• Atoms: The smallest unit of an element that retains its chemical properties.

• Molecules/Compounds: Groups of atoms bonded together; compounds contain atoms of different elements.

• Physical Properties: Characteristics that can be observed without changing the substance's identity (e.g., color, state, melting point, boiling point, density, solubility).

• Chemical Properties: Characteristics that describe a substance's ability to undergo chemical changes (e.g., flammability, reactivity).

Example: Water (H2O) is a compound made of hydrogen and oxygen atoms bonded together.

Physical vs. Chemical Changes

Changes in matter can be classified as physical or chemical:

• Physical Change: Alters the form or appearance of matter but does not make any substance in the matter into a different substance (e.g., melting, boiling, dissolving).

• Chemical Change: Produces matter with a different composition than the original matter (e.g., burning, rusting, reacting acids with bases).

Example: Dissolving sugar in water is a physical change; burning sugar to produce CO2 and H2O is a chemical change.

Separation of Mixtures

Distillation and Other Methods

Mixtures can be separated into their components by physical methods:

• Distillation: Separation based on differences in boiling points.

• Precipitation: Formation of a solid from a solution during a chemical reaction.

• Evaporation: Separation of a liquid from a solution by vaporizing the liquid.

Example: Crude oil is a mixture of hydrocarbons (e.g., octane, butane, propane, hexane) that can be separated by distillation.

Properties of Matter

Density and Intrinsic Properties

Density is an intrinsic property of matter, defined as mass per unit volume:

• Formula:

• Intrinsic properties do not depend on the amount of substance (e.g., density, boiling point).

Example: The density of water is 1.00 g/mL at 25°C.

Thermal Expansion and Specific Heat Capacity

Thermal expansion refers to the increase in volume of a substance due to an increase in temperature. Specific heat capacity is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

• Formula: where = heat, = mass, = specific heat capacity, = change in temperature.

Example: Water has a high specific heat capacity, which helps regulate temperature in the environment.

Measurement in Chemistry

Types of Numbers and Measurement Accuracy

Scientific measurements can be exact or inexact:

• Exact Numbers: Defined values or counted quantities (e.g., 1 dozen = 12).

• Measured Numbers: Obtained using instruments; have uncertainty.

• Accuracy: How close a measurement is to the true value.

• Precision: How reproducible measurements are.

• Percent Error Formula:

Scientific Observations and Laws

Qualitative vs. Quantitative Observations

• Qualitative: Descriptive, subjective (e.g., color, texture).

• Quantitative: Numerical, objective (e.g., mass, volume).

Natural Laws in Chemistry

• Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.

• Law of Definite Proportions: A chemical compound always contains the same elements in the same proportion by mass.

• Law of Multiple Proportions: When elements combine in more than one way, the ratios of the masses of the second element that combine with a fixed mass of the first element are small whole numbers.

Example: 1.50 g H2 + 12.0 g O2 → H2O

Atomic Theory

Dalton's Atomic Theory

• Matter is made of small, indivisible particles called atoms.

• Atoms of each element are identical in mass and properties.

• Atoms cannot be created or destroyed in chemical reactions.

• Chemical reactions involve rearrangement of atoms.

Structure and Properties of Atoms

Subatomic Particles

• Electrons: Negatively charged, much smaller than protons and neutrons.

• Protons: Positively charged, found in the nucleus.

• Neutrons: Neutral, found in the nucleus.

• Mass of electron ≈ 9.11 × 10-31 kg

• Charge of electron = -1.60 × 10-19 C

Forces and Energy in Atoms

• Coulomb's Law: Describes the force between two charges.

• Energy is required to separate charges; energy is released when opposite charges come together.

• Atoms tend to lose energy spontaneously to reach a more stable state.

Periodic Table and Atomic Structure

Atomic Number and Mass Number

• Atomic Number (Z): Number of protons in the nucleus; defines the element.

• Mass Number (A): Total number of protons and neutrons in the nucleus.

Isotopes

• Atoms of the same element with different numbers of neutrons.

• Isotopes have the same atomic number but different mass numbers.

Example: Carbon-12, Carbon-13, and Carbon-14 are isotopes of carbon.

Summary Table: Physical vs. Chemical Properties and Changes

Key Formulas and Concepts

• Density:

• Specific Heat:

• Coulomb's Law:

• Percent Error:

Additional info:

• Some diagrams and tables were referenced in the notes (e.g., distillation apparatus, temperature scales) and have been described in text for clarity.

• Where handwriting was unclear, standard general chemistry context was used to clarify and expand explanations.