Introduction to Matter and Its States

Definition and Properties of Matter

Matter is anything that has mass and takes up space. It exists in several physical states, each with distinct properties.

• Solid: Definite mass and definite shape.

• Liquid: Definite mass but takes the shape of its container.

• Gas (or Vapor): Definite mass but takes both the shape and volume of its container.

• Plasma: Ionized gas, considered the fourth state of matter.

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

Pure Substances and Mixtures

Matter can be classified as pure substances (elements and compounds) or mixtures (combinations of two or more substances).

• Homogeneous Mixtures: Uniform composition throughout, such as solutions.

• Heterogeneous Mixtures: Non-uniform composition, such as a mixture of liquid and solid.

• Air: An example of a mixture.

Structure of the Atom

Atomic Components

An atom consists of a nucleus containing protons and neutrons, surrounded by electrons in orbitals.

• Protons: Positively charged subatomic particles with mass.

• Neutrons: Electrically neutral subatomic particles with mass.

• Electrons: Negatively charged particles with very small mass, occupying distinct energy levels (orbitals).

Octet Rule

The octet rule states that atoms tend to gain, lose, or share electrons to achieve a full outer shell of eight electrons.

• Cations: Positively charged ions (e.g., ).

• Anions: Negatively charged ions (e.g., ).

Elements and the Periodic Table

Common Elements in Biology

• C: Carbon

• O: Oxygen

• N: Nitrogen

• S: Sulfur

• P: Phosphorus

There are 118 known elements: 92 naturally occurring and 26 synthetic (man-made).

Periodic Table Overview

The periodic table organizes elements by atomic number and properties. First created by Dmitri Mendeleev, it shows trends in atomic weight and chemical behavior.

• Atomic Number: Number of protons in the nucleus.

• Atomic Mass: Sum of protons and neutrons.

Isotopes and Radioactivity

Isotopes are forms of an element with different numbers of neutrons, resulting in different atomic masses. Some isotopes are radioactive and emit particles:

• Alpha particles: Helium nuclei ()

• Beta particles: High-energy electrons

• Gamma rays: High-frequency light rays

Atomic weights are weighted averages based on isotope abundance.

Light and the Electromagnetic Spectrum

Types of Electromagnetic Radiation

Light includes a range of electromagnetic waves:

• Radio waves

• Microwaves

• Infrared rays

• Visible light

• Ultraviolet rays

• X-rays

• Gamma rays

These are ranked from low frequency/energy to high frequency/energy.

Molecules and Chemical Bonding

Covalent and Ionic Bonds

Molecules are formed by covalent bonding (sharing of electrons). Ionic compounds are formed by the attraction between positively and negatively charged ions.

Properties of Molecules

• Boiling point

• Melting point

• Density (mass/volume)

• Shape of molecule

• Solubility

Polarity and Non-bonding Associations

• Polar covalent bonds: Uneven distribution of electrons, leading to molecular polarity.

• Non-polar covalent bonds: Even distribution of electrons.

• Hydrogen bonding: Attraction between hydrogen and an electronegative atom (e.g., O, N); contributes to high boiling point.

• Dipole-dipole interactions: Attraction between positive and negative poles of molecules.

• Van der Waals forces: Weak, temporary dipole-dipole attractions.

Water: Properties and Biological Importance

Physical and Chemical Properties of Water

Water is essential for life due to its unique properties:

• Boiling Point: 100°C

• Melting Point: 0°C

• Density: 1 g/cm3 (liquid)

• Frozen water is less dense than liquid water

• Bent geometry

• Polar molecule

• High heat of vaporization

• Good solvent

• Cohesive and adhesive forces

• High surface tension

Water in Living Organisms

Water is vital for various physiological processes in humans:

• Thirst

• Digestion

• Excretion

• Blood circulation

• Dehydration and water toxicity

Acids, Bases, and Buffers

Definitions and Properties

• Acids: Release hydrogen ions () into solution.

• Bases: Release hydroxide ions () into solution.

• pH: Measures acidity; scale from 0 (very acidic) to 14 (very basic), with 7 as neutral.

Buffers

Buffers are chemicals that resist changes in pH when acids or bases are added. In humans, carbonic acid acts as a buffer to maintain metabolic stability.

Life Functions and Classification

Basic Life Functions

• Growth

• Nutrient gathering (nutrition)

• Reproduction

• Excretion

• Transport

• Regulation

• Homeostasis: Regulation of internal environment

Classification Scheme

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

The Scientific Method

Steps in Scientific Investigation

• Observe and identify; use senses

• Make a hypothesis (educated guess)

• Design an experiment

• Control group (everything except variable of interest)

• Experimental group (contains variable of interest)

• Collect data and analyze results

• Avoid bias

• Discuss results and draw conclusions

• Accept or reject hypothesis

Cells and the Hierarchy of Life

Definition of a Living Cell

A living cell is capable of reproducing itself without external help. Viruses and prions are not considered living cells.

Eukaryotes vs. Prokaryotes

• Eukaryotes: Have a true nucleus

• Prokaryotes: Lack a nucleus

Biological Hierarchy

• Biosphere

• Ecosystem

• Communities

• Population

• Species/Organism

• Organ Systems

• Organ

• Tissue

• Cell

• Molecule

• Atom

Additional info: Some explanations and examples have been expanded for clarity and completeness, such as the role of water in biological systems and the steps of the scientific method.