ACT Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Density formula

Density equals mass divided by volume. It determines whether an object sinks or floats in a fluid and is often used to identify unknown materials from measured mass and volume.

Newton's second law

Net force equals mass times acceleration. For a fixed force, greater mass produces smaller acceleration; for fixed mass, greater net force produces greater acceleration.

Ideal gas law

Pressure times volume equals moles times the gas constant times temperature. At constant temperature, doubling pressure halves volume, an inverse relationship described by Boyle's law.

Atomic number

The number of protons in an atom's nucleus. It defines the element's identity; in a neutral atom it also equals the number of electrons.

pH scale meaning

A measure of hydrogen ion concentration where values below 7 are acidic and above 7 are basic. Each one-unit change means a tenfold change in concentration.

DNA base pairing

Adenine pairs with thymine and guanine pairs with cytosine in DNA. In RNA, uracil replaces thymine and pairs with adenine during transcription.

Photosynthesis inputs and outputs

Plants use carbon dioxide, water, and light energy to produce glucose and oxygen. The process converts light energy into chemical energy stored in sugar bonds.

Cellular respiration purpose

Cells break down glucose with oxygen to release energy stored as ATP, producing carbon dioxide and water as byproducts. It is essentially the reverse of photosynthesis.

Kinetic versus potential energy

Kinetic energy is energy of motion, depending on mass and speed squared. Potential energy is stored energy based on position, such as height in a gravitational field.

Conservation of energy

Energy cannot be created or destroyed, only converted between forms. In a closed system, total energy remains constant even as forms change.

Natural selection conditions

Heritable variation exists among individuals, more offspring are produced than survive, and traits affecting survival or reproduction become more common over generations.

Dominant versus recessive alleles

A dominant allele is expressed when at least one copy is present; a recessive allele is expressed only when two copies are present.

Speed versus acceleration

Speed is distance per unit time. Acceleration is the rate of change of velocity, so an object moving at constant speed in a circle is still accelerating.

Electric circuit basics

Ohm's law states voltage equals current times resistance. In a series circuit, current is the same through all components and resistances add.

Independent variable

The variable the experimenter deliberately changes or manipulates. It is plotted on the x-axis, and its effect on the measured outcome is what the study tests.

Dependent variable

The variable that is measured or observed in response to the independent variable. It is plotted on the y-axis and represents the experiment's outcome.

Control group purpose

A group that receives no treatment or a placebo, providing a baseline for comparison. Without it, changes cannot be confidently attributed to the treatment.

Controlled variables

Factors held constant across all groups so they cannot explain differences in the outcome. Examples include temperature, time, and starting material amounts.

Correlation versus causation

Two variables changing together does not prove one causes the other. Causation requires controlled manipulation or strong evidence ruling out confounding variables.

Interpreting slope

Slope equals the change in y divided by the change in x. Its units are y-units per x-unit, and it often represents a rate such as speed or reaction rate.

Interpolation versus extrapolation

Interpolation estimates values between existing data points and is relatively reliable. Extrapolation predicts beyond the measured range and carries greater uncertainty.

Sample size effect

Larger samples and repeated trials reduce the influence of random variation, making results more reliable and differences between groups more trustworthy.

Hypothesis support

Data can support or fail to support a hypothesis but never prove it. A single contradicting result can falsify a hypothesis, which is then revised.

Reading a data table

Locate the row and column for the condition of interest, note the units in headers, and track trends down columns or across rows before drawing conclusions.

Conflicting viewpoints strategy

Identify the specific claim where two scientists disagree, then find which data or assumption each uses. The disagreement usually traces to one differing variable.

Scientific claim evaluation

A valid claim is supported by data from the passage, uses controlled comparisons, and does not rely on assumptions beyond what the study measured.

Percent change calculation

Percent change equals the difference between new and original values divided by the original value, times 100. This quantifies the size of a shift.

Unit consistency check

Before computing, confirm all measurements use the same units. Mixing grams and kilograms or minutes and seconds produces errors in calculated rates.

Graph trend description

State whether the dependent variable increases, decreases, or stays flat as the independent variable rises, and note whether the change is linear or curved.

Experimental design weakness

A common flaw is changing multiple variables at once or lacking a control, which prevents attributing observed effects to any single factor.

Predicting from a graph

Extend the established trend using the slope or curve pattern, but flag predictions outside the plotted range as uncertain since the relationship may change.

Outlier identification

A data point far from the pattern of the other points. It may reflect measurement error or a real anomaly and should be examined, not automatically discarded.