Science: Scientific Method, Properties, Changes, Substances, and Mixtures (Pages 1–5)

Vocabulary flashcards covering key terms from the lecture notes on the scientific method, properties, changes, substances, mixtures, and separation techniques.

Observation

The first step of the scientific method: noticing and recording facts using senses and measurements.

Question

A query that guides the investigation (Why? How? What if?).

Hypothesis

An educated, testable guess about the relationship between variables (If… Then…).

Experiment

A planned test of the hypothesis using controlled variables to isolate effects.

Independent variable

The variable deliberately changed by the experimenter.

Dependent variable

The variable that is measured or observed in an experiment.

Controlled variables

Variables kept the same to ensure a fair test.

Data Collection

Recording results in tables, graphs, or notes.

Analysis

Looking for patterns in the data and comparing results to the hypothesis.

Conclusion

A statement about whether the data supported or refuted the hypothesis.

Repeat / Communicate

Sharing findings with others and repeating the experiment if needed.

Theory

A well-tested explanation of phenomena supported by extensive evidence.

Physical Property

A characteristic observed or measured without changing the substance’s identity (e.g., color, odor, mass, density, melting/boiling point, solubility, conductivity, magnetism, state of matter).

Chemical Property

Describes how a substance reacts or changes into something new (e.g., flammability, reactivity with acid, rusting, tarnishing, toxicity).

Physical Change

A change in form or appearance that does not create a new substance (e.g., cutting, dissolving, melting, breaking).

Chemical Change

A process that produces a new substance; signs include color change, gas formation, temperature change, precipitate, and new odor.

Reversible vs. irreversible changes

If a change is reversible without changing identity, it is physical; if it creates a new substance, it is chemical.

Elements

Pure substances that cannot be broken down; examples: O2, Au, H2.

Compounds

Two or more elements chemically bonded to form a new substance; examples: H2O, CO2, NaCl.

Mixtures

Physical combinations of substances not chemically bonded; can be separated physically.

Homogeneous mixture

Looks the same throughout; also called a solution (examples: saltwater, air, Kool-Aid).

Heterogeneous mixture

Uneven composition with visibly different parts (examples: salad, pizza, trail mix, sand + water).

Solutions

Homogeneous mixtures where particles are evenly dissolved; solvent is the dissolving medium (e.g., water); solute is what is dissolved (e.g., salt).

Solvent

The substance that dissolves another substance; the dissolving medium (e.g., water).

Solute

The substance that is dissolved (e.g., salt).

Colloids

Particles don’t settle and scatter light (Tyndall effect); examples: milk, fog, mayonnaise, gelatin.

Suspensions

Large particles that settle over time; examples: muddy water, oil + water, juice with pulp.

Filtration

Separation of solids from liquids (e.g., sand from water).

Evaporation

Removes liquid, leaving solid behind (e.g., salt from saltwater).

Distillation

Separates substances by boiling points (e.g., purifying water, separating alcohol).

Chromatography

Separates substances by movement through a medium (e.g., ink colors on paper).

Centrifugation

Spins mixtures to separate by density (e.g., components of blood).

Magnetism

Uses magnetic properties to separate magnetic materials (e.g., iron filings from sand).

Decanting

Pouring off liquid, leaving solid behind (e.g., oil from water).

Sieving

Separates particles by size (e.g., flour sifting).

Melting point

The temperature at which a solid changes to a liquid; for ice, 0°C.

Rust

A chemical change where iron reacts with oxygen to form iron oxide.

Oxygen (O)

Element, symbol O; essential element and a component of air; forms rust with iron.

Water (H2O)

A compound formed from hydrogen and oxygen; chemical formula H2O.

Air

A homogeneous mixture of gases (mainly nitrogen and oxygen) that looks uniform.

Salt in water

An example of a solution where salt (NaCl) dissolves in water to form a homogeneous mixture.

salad

A heterogeneous mixture with visibly different parts.

Milk

A colloid in which dispersed particles scatter light and do not settle quickly.

Sand in water

A suspension where large particles settle over time.