RISE Science Grade 7 key terms

A push or a pull that can change an object's speed, direction, or shape. Forces have both a size and a direction and are measured in newtons.

The single combined force that results from adding together every force acting on an object. It decides whether the object's motion will change.

Forces that are equal in size and opposite in direction, so they cancel each other out. Because the net force is zero, the object's motion does not change.

Forces that do not cancel because they are unequal in size or not exactly opposite. They produce a net force and make an object speed up, slow down, or turn.

A noncontact force that pulls objects with mass toward one another. It gets stronger as mass increases and weaker as distance grows; on Earth it pulls objects downward.

A contact force that resists motion when two surfaces rub against each other. It turns motion energy into heat and can slow down or stop a moving object.

Friction between a moving object and the air around it, pushing opposite to the object's motion. It increases as an object moves faster or has more surface area.

The tendency of an object to keep doing what it is already doing, staying at rest or moving in a straight line at constant speed, unless a force acts on it.

The amount of matter in an object, usually measured in kilograms. Mass stays the same no matter where the object is, unlike weight.

The pull of gravity on an object's mass, measured in newtons. Weight changes when the strength of gravity changes, such as on the Moon.

The rule that whenever one object pushes or pulls on another, the second object pushes or pulls back with an equal force in the opposite direction.

The rate at which an object's velocity changes. An object accelerates when it speeds up, slows down, or changes direction, and it is measured in meters per second squared.

A noncontact push or pull between magnets, or between a magnet and certain metals such as iron. It acts at a distance and can attract or repel.

The breaking down of rock into smaller pieces while it stays in place. Water, ice, wind, plant roots, and chemical reactions can all cause it.

The picking up and carrying away of weathered rock, soil, and sediment by water, wind, ice, or gravity. It moves material from one place to another.

The dropping of eroded sediment when the water, wind, or ice carrying it slows down or melts. Deposited material builds up in layers over time.

Loose pieces of rock, sand, silt, and shell that have been broken off and moved by erosion. Sediment settles in layers and can later harden into rock.

Rock that forms when layers of sediment are pressed and cemented together over long periods. It often shows layers and is the rock type most likely to hold fossils.

The preserved remains, imprint, or trace of an ancient living thing, usually found in sedimentary rock. Fossils help scientists compare and order rock layers.

The rule that in undisturbed rock layers, the oldest layer is at the bottom and the youngest is at the top. It helps scientists put past events in order.

The theory that Earth's outer shell is broken into huge moving slabs called plates. Their motions cause earthquakes, volcanoes, and the building of mountains.

A place where two tectonic plates move toward each other and collide. The crust there can be pushed up into mountains or sink into a deep ocean trench.

A place where two tectonic plates move apart. Magma rises into the gap and cools to form new crust, as along mid-ocean ridges.

A crack in Earth's crust where blocks of rock slide past, over, or under one another. Sudden slipping along a fault releases energy as an earthquake.

A sudden shaking of the ground caused by rock breaking or slipping along a fault. The energy travels outward through Earth as seismic waves.

The ongoing set of processes that slowly change rock from one type into another through melting, cooling, heat, pressure, weathering, erosion, and deposition.

The smallest unit of life that can carry out all of life's activities. Every living thing is made of one or more cells.

The thin, flexible covering around a cell that controls which materials enter and leave. It holds the cell together and helps it interact with its surroundings.

A stiff outer layer that surrounds the cells of plants and some other organisms. It supports and protects the cell and gives it a firm shape.

The control center of a cell that contains the genetic material, DNA. It directs the cell's activities, including growth, repair, and reproduction.

The jelly-like material that fills a cell and surrounds the organelles. Many of the cell's chemical reactions take place in it.

The organelles that release energy from food during cellular respiration. Cells that use a lot of energy, such as muscle cells, contain many of them.

The green organelle found in plant cells where photosynthesis takes place. It captures light energy and uses it to make sugar from carbon dioxide and water.

A small structure inside a cell that does a specific job, such as releasing energy or storing water. Its shape is suited to the work it performs.

A group of similar cells that work together to carry out the same job, such as muscle tissue or the tissue inside a leaf.

A structure made of two or more kinds of tissue that work together to do a specific job, such as a heart, a lung, or a leaf.

A group of organs that work together to perform a major job for an organism, such as the digestive system or the circulatory system.

The process in which plants use light energy to combine water and carbon dioxide into sugar, releasing oxygen. It stores energy in food for the plant.

The process cells use to release energy from sugar by combining it with oxygen, producing carbon dioxide and water as waste products.