TExES Science 7-12 (236)

Science is a systematic process of acquiring knowledge about the natural world through observation, experimentation, and evidence-based reasoning. Scientific knowledge is empirical, meaning it is derived from sensory experience and measurable phenomena. Science is characterized by its reliance on testable explanations and its openness to revision based on new evidence.

Scientific knowledge differs from other ways of knowing because it requires verifiable evidence, logical consistency, and reproducibility. Science does not address supernatural explanations, moral judgments, or aesthetic values. The scope of science is limited to questions that can be answered through observation and experimentation.

Scientific inquiry involves asking questions, making observations, forming hypotheses, designing experiments, collecting data, analyzing results, and drawing conclusions. This process is iterative rather than strictly linear. Scientists often move back and forth between steps as new information emerges.

Observation is the foundation of scientific inquiry. Observations can be qualitative (descriptive) or quantitative (numerical). Qualitative observations describe characteristics such as color, texture, or behavior. Quantitative observations involve measurements with specific units and values.

A scientific question must be testable and answerable through investigation. Good scientific questions are specific, measurable, and focused on natural phenomena. Questions that begin with "how" or "what" typically lead to productive investigations.

A hypothesis is a tentative, testable explanation for an observed phenomenon. A well-constructed hypothesis is based on prior knowledge, makes a specific prediction, and can be supported or refuted through experimentation. Hypotheses are often written in an if-then format: "If [independent variable is manipulated], then [dependent variable will respond in a specific way]."

A prediction is a specific, measurable outcome expected if the hypothesis is correct. Predictions must be falsifiable, meaning there must be a possible observation that would prove the prediction wrong. The ability to falsify a hypothesis is a fundamental requirement of scientific reasoning.

A controlled experiment tests a hypothesis by manipulating one variable while keeping all other variables constant. The independent variable is the factor deliberately changed by the experimenter. The dependent variable is the factor measured or observed in response to changes in the independent variable. Controlled variables (constants) are factors kept the same throughout the experiment to ensure a fair test.

The experimental group receives the treatment or manipulation. The control group does not receive the treatment and serves as a baseline for comparison. Controls are essential for determining whether observed effects are due to the independent variable rather than other factors.

Replication involves repeating an experiment multiple times to ensure results are consistent and reliable. Sample size refers to the number of subjects or trials in an experiment. Larger sample sizes generally produce more reliable results by reducing the impact of random variation.

Randomization is the process of assigning subjects to groups by chance to minimize bias. Random assignment helps ensure that groups are equivalent before treatment, so differences observed after treatment can be attributed to the independent variable.

Descriptive investigations involve observing and describing phenomena without manipulating variables. Examples include field studies, surveys, and natural history observations. Descriptive investigations are useful for generating hypotheses and documenting patterns.

Comparative investigations involve comparing two or more groups or conditions without experimental manipulation. Scientists identify naturally occurring differences and analyze their effects. Comparative studies are common in ecology, geology, and evolutionary biology.

Experimental investigations involve manipulating variables under controlled conditions to test cause-and-effect relationships. True experiments include random assignment, manipulation of an independent variable, and measurement of a dependent variable.

A scientific theory is a well-substantiated explanation of a natural phenomenon supported by a large body of evidence. Theories explain why phenomena occur and can be used to make predictions. Major scientific theories include the theory of evolution, cell theory, germ theory of disease, and plate tectonic theory. Theories are not guesses; they represent the highest level of scientific understanding.

A scientific law is a statement that describes an observed pattern or relationship in nature. Laws describe what happens under specific conditions but do not explain why. Examples include Newton's laws of motion, the law of conservation of mass, and Mendel's laws of inheritance. Laws are often expressed mathematically.

Theories and laws are both well-supported by evidence, but they serve different purposes. Theories explain mechanisms, while laws describe patterns. A theory does not become a law; they are different types of scientific knowledge.

Scientific models are representations of objects, systems, or processes that are too large, too small, too complex, or too dangerous to study directly. Models can be physical (three-dimensional objects), mathematical (equations and formulas), or conceptual (diagrams and mental representations).

Models are useful for visualizing structures, testing predictions, and communicating ideas. All models have limitations because they simplify reality. Scientists must recognize which aspects of a model accurately represent the real system and which aspects are approximations.