NYS Grade 8 Science key terms

Anything that has mass and takes up space. Matter exists as solids, liquids, and gases, is made of tiny particles, and is conserved during physical and chemical changes.

The smallest unit of an element that still has that element's properties. Atoms are the building blocks of all matter and combine to form molecules and compounds.

How much mass is packed into a given volume, calculated as mass divided by volume. An object less dense than the fluid around it will float.

The energy an object has because it is moving. Its amount depends on the object's mass and speed, and it increases quickly as speed rises.

Stored energy that depends on an object's position or condition, such as a ball held high above the ground or energy stored in chemical bonds.

The single combined force that results from adding all forces acting on an object. When the net force is zero, the object's motion does not change.

A force that resists sliding when two surfaces touch. Friction can slow objects down and changes motion energy into thermal energy.

The distance between two matching points on a wave, such as from one crest to the next. Wavelength is often measured in meters or nanometers.

The number of complete wave cycles passing a point each second, measured in hertz. Higher frequency waves carry more energy when comparing electromagnetic waves.

A process in which atoms rearrange to form new substances with different properties. Evidence may include color change, gas bubbles, light, or a temperature change.

The rule that in a closed system the total mass before a chemical reaction equals the total mass after, because atoms are only rearranged, never created or destroyed.

A complete closed path that lets electric current flow from a power source through wires and components and back. Breaking the loop stops the current.

The smallest unit of life that can carry out all the processes of living things. Some organisms are a single cell; others are built of many cells.

A specialized structure inside a cell that does a particular job, such as the nucleus storing genetic instructions or chloroplasts capturing light energy for food making.

The process producers such as plants use to turn light energy, water, and carbon dioxide into sugar and oxygen. The sugar stores energy in chemical bonds.

The process cells use to release energy from sugar by combining it with oxygen, giving off carbon dioxide and water. Nearly all living things depend on it.

A long molecule that stores the instructions for building and running an organism. Its sequence of bases is copied and passed on to offspring.

A section of DNA that holds instructions for a single trait or protein. Different versions of a gene create differences such as eye color or blood type.

The process by which individuals with traits better suited to their environment tend to survive and reproduce more, so those helpful traits become more common in later generations.

A body feature or behavior that helps an organism survive and reproduce in its surroundings. Adaptations build up over many generations through natural selection.

All the living organisms in an area together with the nonliving parts they interact with, such as water, soil, air, and sunlight. Energy and matter flow through it.

A diagram that shows how energy moves through an ecosystem as organisms eat and are eaten. Arrows point from the food to the organism that consumes it.

The largest population of a species that an environment can support over time, given the food, water, space, and shelter available there.

The theory that Earth's outer shell is broken into large plates that move slowly over the mantle, causing earthquakes, volcanoes, and mountains where plates meet.

Heat transfer that happens when a fluid circulates, with warmer, less dense material rising and cooler, denser material sinking. It drives plate motion, winds, and ocean currents.

The carrying away of weathered rock, soil, and sediment by water, wind, ice, or gravity. Erosion carves valleys and builds deltas and beaches.

The continuous movement of water among the ocean, atmosphere, and land through evaporation, condensation, precipitation, and runoff. The Sun provides the energy that drives it.

The warming of Earth's surface that occurs when gases such as carbon dioxide and water vapor trap heat that would otherwise escape into space. It keeps Earth warm enough for life.

The average weather patterns of a region over many years, including typical temperature, precipitation, and seasons. Climate is not the same as daily weather.

The changing shapes of the lit portion of the Moon that we see from Earth as the Moon orbits us. One complete cycle takes about 29 days.

The attractive force between any two objects that have mass. Gravity keeps planets in orbit, causes ocean tides, and pulls falling objects toward Earth's center.

The requirements a design must meet to count as successful, such as a maximum cost, a size limit, or a minimum strength.

The limits placed on a design, such as available materials, budget, time, safety rules, or environmental rules. A good solution meets the criteria within these limits.

An early model of a design built to test ideas and uncover problems before the final version is made. Prototypes are often simple, cheap, and easy to change.

One repeat of the design cycle of building, testing, and improving. Engineers use what they learn from each test to make the next version better.

A compromise in which one benefit is given up to gain another, because a design cannot meet every goal perfectly at once.