Scientific Method

Steps in the Scientific Method

The scientific method is a systematic approach used in scientific investigation to answer questions and test hypotheses. The general steps are:

• Puzzling Observation: Noticing something unusual or unexplained in nature.

• Hypothesis: Formulating a tentative explanation or prediction that can be tested.

• Predicted Result / Outcome: Stating what you expect to happen if the hypothesis is correct.

• Planned Test or Experiment: Designing and conducting an experiment to test the hypothesis.

• Observed Result / Outcome: Collecting and analyzing data from the experiment.

• Conclusion: Determining whether the results support or refute the hypothesis.

Variables and Constants

• Variable: A characteristic (property, trait) with values that differ among objects, events, or situations (e.g., hair color, speed).

• Constant: A characteristic that does not differ among objects, events, or situations (e.g., number of noses).

• Experimental/Independent Variable: The variable that is manipulated by the researcher to test its effect.

• Response/Outcome/Dependent Variable: The variable that is measured to assess the effect of the independent variable.

Control and Experimental Groups

• Control Group: A group that does not receive the experimental treatment; used for comparison.

• Experimental Group: The group that receives the treatment or manipulation.

Reducing Bias and Types of Evidence

• Bias: A tendency to favor one explanation or belief; can be reduced by random assignment, placebo, double-blind experiments, large sample size, and replication.

• Types of Evidence:

  • Experimental: Evidence from controlled experiments.

  • Correlational: Evidence showing relationships between variables.

  • Circumstantial: Evidence based on inference from a single data point.

Hypotheses, Theories, and Laws

• Hypothesis: An educated, testable explanation for an observation.

• Theory: A well-substantiated explanation supported by a large body of evidence; broader than a hypothesis.

• Law: A statement based on repeated observations that describes a phenomenon, often mathematically (e.g., Law of Gravity).

Evaluating Scientific Information

• Primary Sources: Original research articles, data, clinical trials.

• Secondary Sources: Reviews, analyses of primary sources.

• Tertiary Sources: Summaries or compilations (encyclopedias, fact sheets).

• Confidence Interval (CI): Range of values likely to include the true value; narrower CI = more precision.

• Statistical Significance (p-value): Probability that results are due to chance; significant if p < 0.05.

Chemistry of Life / Nutrients

Characteristics of Living Things

Living organisms share several key characteristics:

• Composed of biological molecules.

• Basic unit is the cell.

• Ability to grow, reproduce, and respond to stimuli.

• Metabolism: All chemical processes in cells.

• Homeostasis: Regulation of internal conditions.

• Information is passed from parent to offspring.

Atoms and Elements

• Protons (p+): Positively charged, in the nucleus; determine atomic number.

• Neutrons (n0): Neutral, in the nucleus; contribute to mass and stability.

• Electrons (e-): Negatively charged, orbit the nucleus; involved in bonding and reactions.

Types of Chemical Bonding

• Covalent Bonds: Atoms share electrons; can be single, double, or triple bonds.

• Ionic Bonds: Electrons are transferred, creating charged ions (cations and anions) that attract.

• Hydrogen Bonds: Weak attraction between a partially positive hydrogen atom and a partially negative atom (often oxygen or nitrogen).

Electronegativity and Bond Polarity

• Electronegativity: Tendency of an atom to attract electrons; O, N, and F are highly electronegative.

• Polar Covalent Bond: Unequal sharing of electrons; partial charges form (e.g., H2O).

• Nonpolar Covalent Bond: Equal sharing; no charge separation (e.g., CH4).

Hydrophilic vs. Hydrophobic

• Hydrophilic: "Water-loving"; polar or charged; dissolve in water (e.g., salts, sugars).

• Hydrophobic: "Water-fearing"; nonpolar; do not dissolve in water (e.g., oils, lipids).

Properties and Functions of Water

• Water is a polar molecule (one oxygen, two hydrogens).

• Good solvent; dissolves many substances.

• High specific heat; stabilizes temperature.

• Expands when frozen; ice floats.

• Adhesion and cohesion (surface tension, capillary action).

• Can self-dissociate into H+ and OH- ions.

Acids, Bases, and pH

• pH Scale:

• pH > 7: Basic; pH < 7: Acidic; pH = 7: Neutral.

• Acid: Increases [H+] (e.g., HCl).

• Base: Decreases [H+] or increases [OH-] (e.g., NaOH).

• Strong acids/bases can damage cells and proteins.

Macromolecules

There are four main types of biological macromolecules:

• Carbohydrates (CHO):

  • Monomers: Monosaccharides (glucose, fructose).

  • Polymers: Polysaccharides (starch, glycogen, cellulose, chitin).

  • Functions: Short-term energy, structural support (cell walls), dehydration synthesis.

  • Hydrophilic (dissolve in water).

  • Examples: Bread, pasta, fruit, vegetables.

• Lipids (CHO):

  • Monomers: No true monomers.

  • Polymers: No true polymers.

  • Types: Fats (triglycerides), phospholipids, steroids, oils.

  • Functions: Long-term energy storage, insulation, hormones, cell membranes, waterproofing.

  • Hydrophobic (do not dissolve in water).

  • Examples: Fats, oils, butter, olive oil.

• Proteins (CHON):

  • Monomers: Amino acids.

  • Polymers: Polypeptides (fold into proteins).

  • Functions: Enzymes, transport, structural support, hormones, immunity, muscle.

  • Examples: Meat, eggs, beans.

• Nucleic Acids (CHONP):

  • Monomers: Nucleotides.

  • Polymers: DNA and RNA.

  • Functions: Store and transmit genetic information.

  • Examples: Found in all living cells; foods: vegetables.

Dehydration and Hydrolysis Reactions

• Dehydration Synthesis: Links monomers to form polymers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

• Function: Build and break down macromolecules in cells.

Micronutrients vs. Macronutrients

• Micronutrients: Required in small quantities (e.g., vitamins, minerals).

• Macronutrients: Required in large amounts (e.g., carbohydrates, proteins, fats).

• Vitamins: Usually function as coenzymes; only vitamin D can be synthesized in the body (requires sunlight).

• Minerals: Inorganic elements required for various bodily functions.