Intro+to+Chem+-+The+Chemistry+of+Life
The Chemistry of Life
Basic Chemistry
Understanding life requires knowledge of basic chemistry, including atoms and molecules.
All living and nonliving substances are made of matter, which has mass and occupies space.
Atoms are the fundamental units of matter.
What is Matter?
Matter includes anything that has mass and volume.
Examples: A liquid in a beaker and the beaker itself.
Structure of Atoms
Atoms consist of subatomic particles:
Protons: Positively charged particles.
Neutrons: Neutral particles with no charge.
Electrons: Negatively charged particles orbiting the nucleus.
The nucleus is where protons and neutrons are located.
Atom Properties
The unique properties of an atom are determined by the number of protons, electrons, and neutrons.
In a neutral atom, the number of protons equals the number of electrons.
The Periodic Table of Elements
Organizes elements by atomic number (number of protons).
Each element's box contains:
Atomic Number: Important for identifying the element.
Atomic Mass: Combined number of protons and neutrons.
What is an Element?
An element consists of atoms with the same number of protons.
Changes in atomic number result in a different element.
What is an Isotope?
Isotopes are atoms of the same element with a different number of neutrons.
Radioactive isotopes are unstable and can decay.
Summary of Elements
Atoms are made of protons, neutrons, and electrons.
Isotopes possess the same atomic number but differ in atomic mass.
What is a Compound?
Compounds are formed by the combination of two or more elements, yielding new properties distinct from the original elements.
Example: Silicon Dioxide (Quartz).
What is a Molecule?
Molecules consist of two or more atoms bonded together.
Chemical formulas detail the composition of molecules.
How are Bonds Formed?
Bonds form between atoms through valence electrons:
Ionic Bonds: Valence electrons transfer from one atom to another.
Covalent Bonds: Valence electrons are shared between atoms.
Hydrogen Bonds: Weak attractions occur between slightly charged molecules.
Summary of Bonds
Molecules consist of compounds formed by ionic and covalent bonds, with hydrogen bonds being weaker.
Importance of Water
Water, characterized by its polarity, is crucial for all life forms.
Polarity of Water
Polar Molecules: Have unequal charge distribution.
The oxygen end carries a slight negative charge, while the hydrogen end is slightly positive.
Properties of Water Due to Polarity
Cohesion: Water attracts itself (e.g., surface tension).
Adhesion: Water attracts other polar substances.
Unique Properties of Water
Capillary action: Movement upward through thin tubes.
High surface tension: Allows certain organisms to "walk" on water.
High heat of vaporization: More energy is needed for water to evaporate.
Resists temperature changes: Absorbs and releases heat slowly.
Expands when frozen: Ice is less dense than liquid water, causing it to float.
Summary of Water Properties
Water's polarity leads to hydrogen bonds, causing unique properties vital for life.
Water in Solutions
Solutions: Comprise two components; solute (substance dissolved) and solvent (liquid dissolving the solute).
Water is known as the universal solvent, dissolving many substances due to its polarity.
Acids and Bases
Acids: Increase the concentration of H+ ions in a solution; pH below 7.
Bases: Decrease the concentration of H+ ions; pH above 7.
pH Scale
Measures the concentration of H+ ions; each step is a factor of 10.
Neutral: Solutions with a pH of 7.
Summary of Water and pH
Water is a neutral substance and serves as a universal solvent, unlike proteins and acids.