Nagano Entrance Science key terms

A push or pull that can change an object's speed, direction, or shape. Force is measured in newtons and has both size and direction.

A force that opposes sliding between two surfaces in contact. It converts some motion into heat and can slow objects or keep them from starting to move.

When one object pushes or pulls another, the second object pushes or pulls back with equal strength in the opposite direction. The two forces act on different objects.

The energy an object has because it is moving. It increases with mass and with the square of speed, so doubling speed gives four times the kinetic energy.

The rule that energy cannot be created or destroyed. It can only be transferred between objects or changed from one form to another, so total energy stays constant.

The flow of electric charge through a conductor such as a wire. Current is measured in amperes and is driven by a potential difference.

The electrical potential difference between two points that pushes charge around a circuit. It is measured in volts and is sometimes called potential difference.

How much a material or component opposes the flow of electric current. Resistance is measured in ohms; longer, thinner, or hotter wires usually have more resistance.

The number of complete wave cycles that pass a point each second. Frequency is measured in hertz, and higher frequency means a higher-pitched sound or shorter wavelength.

The distance between one point on a wave and the same point on the next cycle, such as from crest to crest. It is usually measured in metres.

The mass of a substance per unit volume, often written as grams per cubic centimetre. Dense materials pack more mass into the same space.

The forms matter takes: solid, liquid, and gas. In solids particles are closely packed and vibrate; in liquids they slide; in gases they move freely.

A change in which atoms are rearranged to form one or more new substances with different properties. Burning, rusting, and cooking are examples.

A starting substance that is used up during a chemical reaction. Reactants are written on the left side of a word or symbol equation.

The smallest particle of an element that still has the properties of that element. It has a nucleus containing protons and neutrons, surrounded by electrons.

A group of two or more atoms joined by chemical bonds. It is the smallest unit of a molecular substance, such as water or oxygen gas.

A pure substance made of atoms of two or more different elements chemically bonded in a fixed ratio. Water and carbon dioxide are compounds.

An atom or group of atoms that has gained or lost electrons and therefore carries a net electric charge. Positive ions have lost electrons; negative ions have gained them.

A scale from 0 to 14 that measures how acidic or alkaline a solution is. Values below 7 are acidic, 7 is neutral, and above 7 is alkaline.

The organs that break food into smaller molecules the body can absorb. It includes the mouth, stomach, small intestine, and large intestine.

The heart, blood vessels, and blood, which together transport oxygen, nutrients, hormones, and wastes around the body. It also helps regulate body temperature and carries immune cells.

The lungs, airways, and breathing muscles that take in oxygen and remove carbon dioxide. Gas exchange happens in tiny air sacs called alveoli.

A section of DNA that carries instructions for making a protein or controlling a trait. Genes are passed from parents to offspring and come in different versions.

One of the alternative versions of a gene. For example, a gene for flower colour may have a purple allele and a white allele.

A trait that appears in an organism when at least one dominant allele is present. The dominant allele masks the effect of a recessive allele in a heterozygote.

A thin, flexible barrier around a cell that controls which substances enter and leave. It is selectively permeable and is made mainly of lipids and proteins.

The organelle in eukaryotic cells that contains most of the cell's DNA and controls many cell activities. It is surrounded by a double membrane.

The process by which plants, algae, and some bacteria use light energy to turn carbon dioxide and water into glucose and oxygen. It occurs mainly in chloroplasts.

An organism that makes its own food, usually by photosynthesis. Producers form the first level of a food chain and supply energy to consumers.

An organism that cannot make its own food and obtains energy by eating other organisms. Consumers may be herbivores, carnivores, or omnivores.

A sequence of organisms in which each is eaten by the next, showing how energy moves from producers to consumers. Arrows point in the direction of energy transfer.

Layers of sedimentary rock laid down one on top of another over long periods. Each layer can preserve fossils and evidence of past environments.

The preserved remains, impression, or trace of an organism that lived long ago, usually found in sedimentary rock. Fossils help show how life and environments changed.

The principle that in undisturbed layers of sedimentary rock, the lowest layer is the oldest and the top layer is the youngest.

The layer of gases surrounding Earth, held by gravity. It is mostly nitrogen and oxygen and protects life from harmful radiation and helps regulate temperature.

The force exerted by the weight of air pressing on a surface. It decreases with height and differences in air pressure cause winds.

The continuous movement of water between Earth's surface and atmosphere through evaporation, condensation, precipitation, and collection. It redistributes fresh water and affects weather.

The spinning of Earth on its imaginary axis. One rotation takes about 24 hours and causes day and night. As Earth rotates, different places face the Sun.

The movement of Earth in its orbit around the Sun, taking about 365.25 days. Combined with Earth's tilted axis, it causes the seasons.

The apparent shape of the Moon as seen from Earth, caused by changing amounts of its sunlit side facing us. The cycle repeats about every 29.5 days.