ACT Science: Reasoning, Data Interpretation, and Experiment Analysis (Full Teaching Notes)

ACT Science section

A test section that primarily measures scientific reasoning and data interpretation rather than recall of obscure science facts.

Scientific reasoning and data interpretation

The skill of extracting information from visuals, understanding experiments, connecting evidence to claims, and comparing competing explanations.

Data Representation

A common ACT Science passage type made up mostly of graphs and tables, where the main task is reading visuals accurately.

Research Summaries

A passage type that presents one or more experiments, requiring you to identify variables, controls, and what the results mean.

Conflicting Viewpoints

A passage type in which multiple students or scientists present different explanations, and you must compare their claims and evidence.

Direct lookup question

A question that asks for a specific value directly from a figure or table, such as 'According to Figure 2…'.

Trend question

A question that asks how a variable changes across a range, such as whether it increases, decreases, or stays constant.

Viewpoint mapping

The process of tracking what each student or scientist believes so you can answer agreement, disagreement, and evidence questions accurately.

x-axis

The horizontal axis on a graph, usually showing the input or condition being changed.

y-axis

The vertical axis on a graph, usually showing the output or measured response.

Units

The measurement labels attached to quantities, such as seconds, meters, or mg/L, which must be read correctly to avoid wrong answers.

Scale

The amount each grid step or interval on an axis represents on a graph.

Non-zero axis

An axis that starts at a value other than zero, which can make differences look larger than they really are.

Interpolation

Estimating a value between two data points that are shown on a graph or table.

Extrapolation

Predicting a value beyond the range of the data shown, which is usually less reliable than interpolation.

Positive relationship

A pattern in which y increases as x increases.

Negative relationship

A pattern in which y decreases as x increases.

Plateau

A graph shape in which a value increases and then levels off with little or no further change.

Threshold

A point at which little change is followed by a rapid change once a certain value is reached.

Line of best fit

A line that represents the overall trend of scattered data points, helping you estimate the general relationship.

Outlier

A data point that lies far from the overall pattern of the rest of the data.

Independent variable

The factor an experimenter changes on purpose to test its effect.

Dependent variable

The outcome that is measured in an experiment.

Controlled variables

Factors kept the same across trials so they do not affect the outcome.

Control condition

A baseline condition used for comparison, often lacking the factor being tested.

Correlation

A relationship in which two variables change together without necessarily proving that one causes the other.

Causation

A relationship in which changing one variable actually produces a change in another.

Repeated trials

Multiple runs of an experiment that improve reliability by reducing the impact of random error.

Measurement precision

How finely a quantity is measured; more reported digits usually indicate greater precision.

Confounding variable

An uncontrolled factor that changes along with the independent variable, making it unclear what caused the result.

Placebo

A treatment that looks like the real treatment but lacks the active ingredient, used to control for psychological or procedural effects.

Random error

Unpredictable variation in measurements that can be reduced by repeating trials and averaging results.

Systematic error

A consistent bias in measurement, such as an instrument that always reads too high, which repetition alone does not fix.

Slope

The rate of change between two variables on a graph, calculated as Δy divided by Δx.

Rate

A measure of how one quantity changes relative to another, often shown as a slope or a 'per' value.

Percent change

The change from an old value to a new value divided by the old value, then multiplied by 100%.

Proportional reasoning

Using factors like doubling or tripling to determine how one variable changes relative to another.

Dimensional analysis

A unit-based method for checking calculations and conversions by making sure units cancel correctly.

Diagram literacy

The skill of reading labels, legends, arrows, and panel changes in diagrams the way you would read a map.

Particle diagram

A visual model showing particles with different shapes, colors, or spacing to represent substances, mixtures, or states of matter.

Energy and process diagram

A diagram that uses arrows and labels to show steps in a process or whether energy is entering or leaving a system.

Diffusion

The movement of particles from an area of higher concentration to an area of lower concentration.

Osmosis

The movement of water across a membrane toward the side with higher solute concentration.

Enzyme

A biological catalyst that speeds up reactions and often appears in ACT Science passages involving rates and plateaus.

pH

A measure of acidity or basicity, where lower pH is more acidic and higher pH is more basic.

Concentration

The amount of solute relative to the amount of solvent or solution.

Position-time graph

A motion graph in which a steeper line indicates a higher speed.

Velocity-time graph

A graph showing velocity over time, where values above zero indicate motion in the positive direction and values below zero indicate the opposite direction.

Cross-figure synthesis

Combining information from two visuals or from text and data to answer a question.

Bridge variable

A shared variable, often time, used to connect information from one figure to another.