Scientific Method and Experimental Design

Key Vocabulary and Concepts

The scientific method is a systematic approach to investigation, involving observation, hypothesis formation, experimentation, and analysis. Understanding key terms is essential for designing and interpreting experiments.

• Precision: The degree to which repeated measurements under unchanged conditions show the same results.

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

• Dependent Variable: The variable being tested and measured in an experiment; it is affected by changes in the independent variable.

• Independent Variable: The variable that is changed or controlled in a scientific experiment to test its effects on the dependent variable.

• Controlled Experiment: An experiment in which only one variable is changed at a time, while all others are kept constant.

• Hypothesis: A testable statement or prediction about the relationship between variables.

Metric System and Measurement

• Metric units include grams (mass), liters (volume), and meters (length).

• Common prefixes: kilo-, centi-, milli-, micro-, nano-.

• Scientific notation is used to express very large or small numbers.

• Example:

Graphing and Data Analysis

• X-axis: Independent variable.

• Y-axis: Dependent variable.

• Types of graphs: bar graph, line graph, scatter plot, pie chart.

Scientific Method Steps

• Observation

• Hypothesis formation

• Experimentation

• Conclusion

Laboratory Equipment

• Graduated cylinder: measures liquid volume.

• Electronic balance: measures mass.

• Meter stick: measures length.

• Pipette: transfers small volumes of liquid.

Atoms, Molecules, and Chemical Reactions

Key Vocabulary

Understanding atomic structure and chemical properties is fundamental to biology, as all living things are composed of atoms and molecules.

• Atom: The basic unit of matter, consisting of protons, neutrons, and electrons.

• Molecule: Two or more atoms bonded together.

• Covalent bond: A chemical bond formed by the sharing of electron pairs between atoms.

• Ionic bond: A bond formed by the transfer of electrons from one atom to another.

• Hydrogen bond: A weak bond between two molecules resulting from an electrostatic attraction.

• Chemical reaction: A process that leads to the transformation of one set of chemical substances to another.

• Solution: A homogeneous mixture of two or more substances.

• Solvent: The substance in which the solute is dissolved.

• Solute: The substance dissolved in the solvent.

Atomic Structure and Periodic Table

• Atoms are composed of protons, neutrons, and electrons.

• The periodic table organizes elements by atomic number and properties.

• Example: H (hydrogen), O (oxygen), Na (sodium).

Chemical Reactions in Aqueous Solutions

• Many biological reactions occur in water-based (aqueous) solutions.

• Example: Dissociation of sodium chloride () in water.

Predicting Chemical Changes

• Use the periodic table and chemical formulas to predict products of reactions.

• Example:

Structural Formulas

• Structural formulas show how atoms are connected in a molecule.

• Example: Organic compounds such as glucose ().

Density and the Scientific Method

Key Vocabulary

• Density: Mass per unit volume of a substance.

• Displacement: The volume of liquid displaced by an object, used to measure volume.

• Volume: The amount of space an object occupies.

• Mass: The amount of matter in an object.

Calculating Density

• Density formula:

• Units: or

• Measure mass using a balance; measure volume by displacement or geometric calculation.

Application

• Determining if an object will float or sink in water.

• Comparing densities of different substances.

Buffers and pH

Key Vocabulary

• pH: A measure of the hydrogen ion concentration; scale ranges from 0 (acidic) to 14 (basic).

• Buffer: A solution that resists changes in pH when acid or base is added.

• Acid: Substance that increases the concentration of hydrogen ions () in solution.

• Base: Substance that decreases the concentration of hydrogen ions in solution.

Calculating pH

• pH formula:

• Example: If , then

Buffer Function

• Buffers maintain stable pH in biological systems.

• Example: Blood contains bicarbonate buffer system.

Effect of Acid/Base Addition

• Adding acid lowers pH; adding base raises pH.

• Buffered solutions resist these changes.

Introduction to Microscopes

Compound Microscope Parts and Functions

Microscopes are essential tools for observing cells and microorganisms. Understanding their parts and how to use them is fundamental in biology labs.

• Base: Supports the microscope.

• Arm: Used for carrying the microscope.

• Coarse/Fine Focusing Knobs: Adjust focus.

• Objective Lenses: Magnify the specimen.

• Stage: Platform for slides.

• Condenser: Focuses light on the specimen.

• Iris Diaphragm: Controls light intensity.

• Lamp: Provides illumination.

Microscope Calculations

• Field of view (FOV), depth of field, contrast, resolution.

• Total magnification:

FOV Diameter Calculation

• FOV diameter can be calculated if known for one objective.

• Example: If FOV at 10x is 2 mm, at 40x it is 0.5 mm.

Microscope Types

• Compound microscope: Used for thin, stained slides.

• Dissecting microscope: Used for larger specimens (e.g., rocks, twigs).

Cell Structure and Function

Key Vocabulary

• Cytoplasm Streaming: Movement of cytoplasm within a cell.

• Cilia: Short, hair-like structures for movement.

• Pseudopodia: Temporary projections for movement and feeding.

• Photosynthesis: Process by which plants convert light energy into chemical energy.

• Thylakoid: Membranous structures within chloroplasts where photosynthesis occurs.

Cell Types and Staining

• Plant cells have cell walls; animal cells do not.

• Protozoa are single-celled eukaryotes.

• Stains are used to visualize cell structures.

Examples of Cell Types

• Cyanobacteria – Oscillatoria

• Amoeba

• Spirogyra

• Onion cell

• Epithelial (Cheek Cell)

• Paramecium

• Euglena

Diffusion and Osmosis

Key Vocabulary

• Diffusion: Movement of molecules from an area of higher concentration to lower concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Hypotonic: Solution with lower solute concentration than the cell; cell may swell.

• Hypertonic: Solution with higher solute concentration than the cell; cell may shrink.

• Isotonic: Solution with equal solute concentration as the cell; no net movement of water.

• Crenation: Shrinking of animal cells in hypertonic solution.

• Plasmolysis: Shrinking of plant cell cytoplasm in hypertonic solution.

• Concentration Gradient: Difference in concentration across a space.

• Solvent: Substance that dissolves the solute.

• Solute: Substance dissolved in the solvent.

• Solution: Homogeneous mixture of solute and solvent.

Diffusion and Osmosis Experiments

• Substances move across membranes by diffusion and osmosis.

• Example: Dialysis tubing experiment with starch, glucose, and iodine.

Effects of Tonicity

• Cells in hypotonic solution: water enters, cell swells.

• Cells in hypertonic solution: water leaves, cell shrinks.

• Cells in isotonic solution: no net water movement.

Visual Effects on Cells

• Plant cells: plasmolysis in hypertonic solution.

• Animal cells: crenation in hypertonic solution.

HTML Table: Solution Tonicity Effects on Cells