Science test one definitions

Hurst. Year 7.

Hazard

Can cause harm

Risk

The chance a hazard will cause harm

Independent Variable

What we change in an experiment

Dependent Variable

What we measure in an experiment

Control variable

What we keep the same in an experiment

Solid

A substance that has a fixed shape and a fixed volume. It cannot be compressed.

Liquid

A substance that does not have a fixed shape, but has a fixed volume. It cannot be compressed.

Gas

A substance that does not have a fixed shape or volume. It can be compressed.

Melting

A change of state from solid to liquid

Evaporation

A change of state when a liquid slowly turns into a gas below its boiling point

Boiling

A change of state from liquid to gas

Condensation

A change of state from gas to liquid

Freezing

A change of state from liquid to solid

Sublimation

A change of state from solid to gas

Cell

The basic building block of life. All living things are made out of cells.

Nucleus

Structure within the cell that contains DNA and controls the cell

Cytoplasm

Jelly-like substance where cell reaction takes place

Mitochondria

The organelle where respiration occurs in a cell

Cell membrane

Controls what moves in and out of a cell

Cell wall

Protects the cell structure, only in a plant cell

Vacuole

Contains cell sap and supports plant cells

Chloroplast

Organelle where photosynthesis occurs. Contains chlorophyll

Tissue

A group of similar cells working together to carry out a particular function

Organ

A group of tissues working together to carry out a particular function

Organ system

A group of organs working together to carry out a particular function

Organelle

Small structures within cells

Force

A push or pull on an object

Contact force

A force exerted when two objects are touching each other

Non-contact force

A force exerted when two objects are not touching each other

Resultant force

The overall force on an object. A measure of how unbalanced forces are.

Weight

The force acting down on an object. It happens as a result of the gravitational pull of the planet you are on.

Mass

The amount of matter contained in an object. It is measured in kilograms or grams

Gravity

The pull on you towards the centre of the earth

Friction

A force which always acts opposite to the direction of motion

Speed

A measure of how fast or slow an object is moving. It can be measured using various units, including metres per second (m/s) or miles per hour (mph).

Distance

A measure of length between two points, usually measured in metres (m).

Time

A measure of how long it takes something to happen, usually measured in seconds (s).

Accelerate

When an object’s speed increases

Decelerate

When an object’s speed decreases

Light gate

A device used to measure speed by detecting when an object interrupts a light ray as it passes through the gate.

Atom

The smallest stable part of an element

Element

A simple substance that cannot be broken down, made of one type of atom.

Group

A column of elements in the periodic table

Period

A row of elements in the periodic table

Compound

A group of elements chemically bonded together

Mixture

A group of two or more elements that are not chemically combined.

Chemical change

A non reversable change where a new substance is formed

Physical change

A reversible change in which new substances are not made

Solvent

A liquid that can dissolve a solute

Solute

A solid that can be dissolved in a solution.

Solution

A mixture of solvent and solute

Saturated

A solution in which the maximum amount of solute is dissolved.

Solubility

How soluble a solute is in a given solvent.

Breathing

The process of moving air into and out of the lungs

Diffusion

The movement of particles from high to low concentration

Lungs

Organs that allow for gas exchange.

Diaphragm

A sheet of muscle that contracts to allow inhalation.

Trachea

The windpipe that carries air from the mouth to the lungs.

Bronchi

Two tubes, each leading to a lung.

Bronchioles

Smaller branches/tubes leading to the alveoli

Alveoli

Small air sacs where oxygen is absorbed

Rib cage

Bones that protect the lungs

Inhale

When air is taken into the lungs

Exhale

When air is removed from the lungs

Respiration

A reaction in which energy is released from glucose—occurs in all living cells.

Chlorophyll

A green pigment that absorbs light for photosynthesis.

Photosynthesis

Plant cells gain energy from the sun

Starch

Glucose stored as a large molecule or polymer—starch.

Iodine

A substance that tests for starch and will turn blue-black when present