Introduction to Science and Logic

Science

• Science is a systematic and logical approach to discovering how things work.
• It's derived from the Latin word "scientia" meaning knowledge.
• Science covers many different topics.

Science vs. Anecdote

• Anecdotes, individual stories, can suggest areas for scientific investigation but are not reliable evidence.
• Scientific understanding relies on large samples and average outcomes.
• Example: A single child developing autism after vaccination does not prove a link, large-scale studies show no correlation between vaccines and autism.

Science Disciplines

• Physics
• Chemistry
• Astronomy
• Logic
• Biology
• Mathematics
• Computer Science
• Geology

Logical Thinking Methods

Inductive Reasoning

• Uses related observations to draw general conclusions.
• Data can be qualitative or quantitative.
• Requires large amounts of data.

Deductive Reasoning

• Uses a hypothesis to predict specific results in controlled experiments.
• This is the foundation of the scientific method.

Scientific Method

• First documented by Sir Francis Bacon in the 1500s.
• Requires empirical or measurable evidence.
• Results must be repeatable.

Hypothesis

• An explanation based on limited evidence that can be tested.
• Must be testable and falsifiable.
• Can be disproven but never proven.

Experiments

• Designed to test a hypothesis.
• Variables:
• Independent variable (what is changed)
• Dependent variable (what is measured)
• Controlled variables are kept constant.

Challenge Statement

• Hypothesis can lead to theories and laws, but this is not a linear process.
• Strong agreement and consistent evidence are needed to move from hypothesis to theory, and theory to law.

Hypothesis, Theories, & Laws

• Long-standing hypotheses can become theories.
• Theories can't be proven and never become laws.
• Laws are consistently proven observations, often represented by mathematical equations, like E=mc2.

Basic Science vs. Applied Science

• Basic science pursues knowledge for the sake of understanding, regardless of immediate benefit.
• Applied science develops technology to address real-world problems.

Chemistry is Important to Understand Biology

• The human body is composed of protons, neutrons, and electrons.

What are Elements

• Elements are the building blocks of matter.

Anatomy of an Atom

• Atoms are composed of subatomic particles:
  • Protons: Positively charged
  • Electrons: Negatively charged
  • Neutrons: No charge

Atoms

• Atoms contain all properties of an element
• Mass number is the sum of protons and neutrons
  • Electrons have negligible mass
• Atomic number equals the number of protons
• The number of protons generally equals the number of electrons

Reading the Periodic Table

• Columns represent the number of electrons in the outer shell
• Rows represent the number of electron shells

Understanding Valence Electrons

• Valence electrons are located in the outermost shell and determine the atom's reactivity.

Chemical Bonds

• Atoms seek to fill their outer electron shells for greater stability.
• Outer shells can be filled by:
  • Sharing electrons (covalent bonds)
  • Donating electrons (ionic bonds)
  • Accepting electrons (ionic bonds)
• Most outer shells hold 8 electrons (octet rule)

Ions & Ionic Bonds

• Ions are atoms with an unequal number of protons and electrons.
  • Cations have a positive charge and have lost electrons
  • Anions have a negative charge and have gained electrons
• Electrons are transferred in ionic bonds, resulting in:
  • Cations donating electrons
  • Anions accepting electrons
• Ionic bonds are very strong and result in the octet rule being satisfied
  • For example, in sodium chloride (NaCl):
    • Sodium (Na) donates an electron
    • Chlorine (Cl) accepts an electron
    • both achieve a stable outer shell

Covalent Bonds

• Covalent bonds occur when atoms share electrons to fill their outer shells.
• They are the strongest and most common type of bond in living organisms.
• Covalent bonds do not dissociate in water, unlike ionic bonds.
• Covalent bonds can be:
  • Polar: Unequal sharing of electrons due to differences in electronegativity (example: water)
  • Nonpolar: Equal sharing of electrons (example: methane)

Hydrogen Bonds

• Hydrogen bonds are weak bonds between polar covalent molecules containing hydrogen.
• The positively charged hydrogen atom attracts the negatively charged portion of another molecule.
• These bonds are responsible for many of water's life-sustaining properties.

Van Der Waals Interactions

• Weak attractive forces between molecules due to temporary partial charges caused by electron movement

Isotopes & Carbon Dating

• Isotopes are atoms of the same element with different numbers of neutrons.
  • Example: Carbon-12 and Carbon-14
• Some isotopes are radioactive and decay over time.
  • The decay process involves neutrons transforming into protons
• Carbon dating utilizes the predictable decay rate of Carbon-14 to estimate the age of fossils and artifacts.
  • Every 5,730 years, half of Carbon-14 decays into Nitrogen-14
  • The concentration of Carbon-14 in remains is compared to its concentration in the atmosphere.

Anatomy of an Atom: Changing Subatomic Particles

• Changing the number of protons creates a new element.
• Changing the number of electrons creates an ion.
• Changing the number of neutrons creates an isotope.

All about pH

• Water constantly dissociates into H+ and OH- ions and reforms back into water.
• pH is a measure of hydrogen ion (H+) concentration.
  • pH 7 is neutral (equal H+ and OH-)
  • pH < 7 is acidic (more H+)
  • pH > 7 is basic (more OH-)
• The pH scale is logarithmic, meaning each unit represents a 10x change in H+ concentration.

Calculating H+ Concentration from pH

• The pH is the negative logarithm of the H+ ion concentration.
• Equation: pH = - log10(H+)

All about pH

• The human body maintains a pH range of 7.2 to 7.6.
• Buffers help maintain pH stability.
• Carbon dioxide (CO2) is crucial to our buffer system.

Carbonic Acid-Bicarbonate Buffer System

• When blood pH rises (becomes more basic):
  • Carbonic acid (H2CO3) dissociates into bicarbonate (HCO3-) and H+, reducing the pH.
    • Reaction: H2CO3 -----> HCO3- + H+
• When blood pH drops (becomes more acidic):
  • Bicarbonate (HCO3-) combines with H+ to form carbonic acid (H2CO3), increasing the pH.
    • Reaction: HCO3- + H+ -----> H2CO3