MTTC Integrated Science (Elementary) (093) key terms

A testable, tentative explanation for an observed phenomenon, stated so that it predicts a specific outcome that investigation could confirm or contradict. It must be falsifiable, meaning evidence could possibly show it to be wrong.

The factor in an experiment that the investigator deliberately changes or selects between conditions, so its effect on the outcome can be measured. It is the presumed cause being tested.

The measured outcome in an experiment, recorded and compared across conditions. Its value depends on what the investigator manipulates, and by convention it is graphed on the vertical axis.

The comparison condition in an experiment that receives no treatment or a neutral treatment, so the effect of the manipulated factor can be isolated. It differs from the experimental group only in the variable under test.

A conclusion drawn from observations combined with prior knowledge, rather than from something directly sensed. For example, footprints in mud support an inference about an animal that was never seen.

Measurements expressed as numbers with units, such as mass in grams or temperature in degrees Celsius. They can be averaged, graphed, and analyzed statistically, unlike descriptive observations.

Repeating an investigation, either by the original researcher or by independent scientists, to see whether the same results occur. Consistent results raise confidence; repeated failure to reproduce suggests error or chance.

A broad, well-tested explanation supported by many lines of evidence and accepted by the scientific community, such as the theory of evolution. In science it does not mean a guess or hunch.

A concise statement, often mathematical, describing a consistent pattern observed in nature, such as Newton's law of gravitation. Laws describe regularities; they do not by themselves explain why the pattern occurs.

The smallest unit that can carry out all of the activities of life, bounded by a membrane. Some organisms are single cells, while others, including humans, are built of many specialized cells.

The process by which plants, algae, and some bacteria use light energy to convert carbon dioxide and water into sugar, releasing oxygen. It stores energy in chemical bonds and supplies most food chains.

The set of reactions in cells that break down sugar in the presence of oxygen to release usable energy, producing carbon dioxide and water as wastes. It occurs in most living organisms, including plants.

The long molecule that stores hereditary information in a sequence of bases. Segments of DNA form genes, which direct protein building and are copied and passed to offspring.

A segment of DNA that carries instructions for making a protein or otherwise influences a trait. Different versions of a gene, called alleles, can produce variation among individuals.

The process by which individuals with inherited traits that improve survival and reproduction in a given environment leave more offspring, so those traits become more common over generations.

An inherited feature or behavior that helps an organism survive and reproduce in its environment, such as thick fur in cold climates. Adaptations arise over generations through natural selection, not by choice.

A community of living organisms interacting with one another and with the nonliving parts of their environment, such as soil, water, and sunlight. Energy flows through it and matter cycles within it.

The tendency of living systems to maintain stable internal conditions, such as body temperature or blood sugar, despite changes outside. It usually involves feedback loops that detect and correct deviations.

The theory that Earth's rigid outer shell is broken into plates that move slowly over the softer mantle. Their collisions, separations, and slides build mountains and cause earthquakes and volcanoes.

The set of processes that transform rock among igneous, sedimentary, and metamorphic forms through melting, cooling, weathering, compaction, and heat and pressure. Any rock type can change into another.

The breakdown of rock in place into smaller pieces or dissolved material by water, ice, plants, and chemical reactions. Weathered material may later be picked up and carried away by erosion.

The transport of weathered rock and soil from one place to another by water, wind, ice, or gravity. It sculpts landforms and, when accelerated by human land use, removes fertile topsoil.

The continuous circulation of water among oceans, atmosphere, land, and living things through evaporation, transpiration, condensation, precipitation, and runoff. The total amount of water on Earth stays roughly constant.

The warming of a planet's surface because certain atmospheric gases absorb and re-radiate outgoing heat. It keeps Earth habitable, but added gases from burning fuels intensify it.

The roughly 23.5-degree tilt of Earth's rotation axis relative to its orbital plane. As Earth orbits the Sun, this tilt changes the angle and duration of sunlight, producing the seasons.

The changing portion of the Moon's sunlit half that faces Earth as the Moon orbits us, from new to full and back over about a month. Phases are not caused by Earth's shadow.

The layer of gases held around a planet by gravity. Earth's is mostly nitrogen and oxygen, and it moderates temperature, blocks harmful radiation, and enables weather and life.

A sudden release of built-up strain energy along a fault in Earth's crust, sending seismic waves outward. The point of origin underground is the focus; the surface point above it is the epicenter.

The smallest unit of an element that keeps that element's properties, consisting of a nucleus of protons and neutrons with electrons around it. Atoms combine to form compounds.

A pure substance made of only one kind of atom, which cannot be broken into simpler substances by ordinary chemical means. Elements are organized on the periodic table by atomic number.

A substance formed when atoms of two or more elements bond in fixed proportions, such as water or table salt. Its properties differ from those of the elements it contains.

Mass per unit volume of a material, often expressed in grams per cubic centimeter. It determines whether an object floats or sinks in a fluid and does not depend on sample size.

The tendency of an object to resist changes in its motion, described by Newton's first law. An object at rest stays at rest, and a moving object keeps moving, unless a net force acts.

The energy an object possesses because of its motion, increasing with both mass and speed. Doubling an object's speed gives it about four times as much kinetic energy.

Stored energy that an object has because of its position or condition, such as a raised mass or a stretched spring. It is released when the object moves or returns to its resting shape.

Heat transfer through direct contact, as energy passes from faster-moving particles to slower ones in a material. Solids, especially metals, conduct well because their particles are close together.

A closed loop through which electric charge can flow, containing a source of voltage and a load such as a bulb. Breaking the loop stops the current, which is why a switch controls a device.

The distance between corresponding points on consecutive waves, such as from crest to crest. It relates inversely to frequency and helps determine the color of light or the pitch of sound.