Download Science Revision – Definitions **these definitions are worth full

Science Revision – Definitions
**these definitions are worth full marks in exam situations. Many of them might not be full
sentences but they contain buzz words which are worth marks**
Biology
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Nutrition- the way an organism gets its food
Respiration- the release of energy from food
Excretion- the removal of waste matter from the body
Growth- the organism gets bigger
Reproduction- the formation of new organisms
Movement- the organism moves
Response- reacting to changes in the surroundings
Invertebrates- animals that don’t have a backbone e.g. earthworm
Vertebrates- animals that have a backbone e.g. dog
Tissue- a group of cells which carry out the same function
An organ- a structure that contains 2 or more tissues working together
A system- a number of organs working together
Digestion- the breakdown of food
Enzyme- a protein that speeds up a reaction without being used up
Product- the substance produced as a result of the action of an enzyme
Substrate- the substances that an enzyme acts on
Joint- where bones meet
Tendons- join muscle to bone
Ligaments- join bone to bone
Antagonistic pair- two muscles which carry out opposite effects
Cartilage- protects the ends of bones
Neuron- a nerve cell
Puberty- the age at which young people reach sexual maturity
Menstrual cycle- a series of changes that take place in the female body every
28 days
Ovulation- the release of an egg from the ovary
Fertilisation- the joining of the male and female gamete to form a zygote
Implantation- the attachment of the embryo to the lining of the uterus
Pregnancy- the carrying of an embryo in the uterus
Contraception- the prevention of fertilisation or pregnancy
 Genetics- the study of how traits or characteristics are inherited
 Chromosomes- thread like structures made of DNA and protein found in the
nucleus of the cell
 Transpiration- the loss of water vapour from a plant
 Xylem- tissue that transports water
 Phloem- tissue that transports food
 Photosynthesis- the way in which green plants make food
 Tropism- the change in growth of a plant in response to a stimulus
 Geotropism- the change in growth of a plant in response to gravity
 Asexual reproduction- new individuals are formed from only one parent
 Runners- a method of asexual reproduction in plants
 Pollination- the transfer of pollen from a stamen to a carpel
 Dispersal- the carrying of the seed as far as possible from the parent plant
 Germination- the growth of a seed to form a new plant
 Ecology- the study of the relationships between plants, animals and their
environment
 Ecosystems- all the plants and animals in an area interacting with each other
and their environment
 Habitat- the area where a plant or animal lives
 Producers- plants that make their own food
 Consumers- animals that get their food by eating plants or other animals
 Herbivore- an animal that eats plants only
 Carnivore- an animal that eats other animals only
 Omnivore- an animal that eats both plants and animals
 Decomposer- organisms that feed on dead plants and animals
 Competition- takes place when 2 or more organisms require something that
is in short supply
 Food web- two or more interconnected food chains
 Interdependence- living things depend on each other for survival
 Conservation- the protection and wise management of natural resources to
prevent living things becoming extinct
 Pollution- the addition of unwanted material to the environment
 Microbiology- the study of small living things
Chemistry Matter- anything that occupies space and has mass
 Solute- the substance being dissolved Solvent- the liquid the solute is dissolving in
 Saturated solution- a solution that contains as much dissolved solute as
possible at that temperature
 Crystallisation- the forming of crystals by cooling a saturated solution
 Mixture- consists of 2 or more substances mingled together, but not
chemically combined
 An element- a substance made up of only one type of atom
 A molecule- composed of 2 or more atoms chemically combined
 Compounds- consists of 2 or more elements chemically combined
 An atom- the smallest part of an element which still has the properties of
that element
 Atomic number- the number of protons in an atom of that element
 Mass number- the amount of protons and neutrons in an atom of that
element
 Isotopes- atoms of the same element which have a different number of
neutrons
 An ionic bond- the force of attraction between oppositely charged ions
 An ion- a charged atom or group of atoms
 A covalent bond- atoms sharing pairs of electrons in order to get a full outer
shell
 Alloy- a mixture of metals e.g. bronze
 Rusting- the corrosion of iron
 Malleable- metal that can be hammered into shape
 Ductile- metal that can be stretched
 Fuel- a substance that burns in oxygen to produce heat
 Fossil fuels- formed from the remains of organisms that lived millions of
years ago
 Hydrocarbons- compounds made up of hydrogen and carbon
 The PH scale- indicates the acidity or basicity of a solution
 Catalyst- a substance that speeds up a reaction without getting used up
 Screening- water passes through a wire mesh and large particles are
removed
 Settling- water is left in large tanks and alum is added to clump smaller
particles together and they sink to the bottom
 Filtration- water is passed through beds of sand to remove insoluble
particles
 Chlorination- chlorine is added to kill bacteria
 Fluoridation- fluorine is added to prevent tooth decay
 Electrolysis- the splitting of a compound by passing electricity through it
 Meniscus- the curved surface of a liquid in a vessel
 Hard water- water that doesn’t produce a lather easily
 Soft water- water that produces a lather easily
 Polymerisation- small repeating units called monomers join together to form
a large molecule called a polymer
Physics
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Length- the distance between 2 points
Mass- the amount of matter an object contains
Volume- how much space an object takes up
Speed- the distance travelled by an object in one unit of time
Velocity- the speed of an object in any given direction
Acceleration- the change in space divided by the time taken
Force- causes a stationary object to move
Friction- a force that opposes the sliding motion of an object when in contact
with another object
Lubrication- used to reduce friction between 2 surfaces in contact
Weight- the pull of the earth on an object
Hooke’s law- the extension of an elastic body is directly proportional to the
force causing the extension
Lever- a rigid body that can turn about a fixed point called the fulcrum
Law of the lever- when a lever is balanced the sum of its clockwise moments
equals the sum of its anticlockwise moments
Centre of gravity- a point in an object where all its weight appears to act
Pressure- the amount of force acting on a unit of area
Work- force by distance
Power- the rate at which work is done
Energy- the ability to do work
Latent heat- energy that causes a change in state and not in temperature
Dispersion- the spreading of light into its different colours
Reflection- the bouncing off of light
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Refraction- the bending of light as it passes from one medium to another
Sound- produced when objects vibrate
Magnetic force- the force of attraction or repulsion between 2 magnets
Magnetic field- the region around a magnet in which the magnetic force can
be detected
Insulator- a material through which charge cannot flow
Conductor- a material through which charge can flow
Direct current (d.c.)- a current that flows in one direction only
Alternating current (a.c.)- a current that flows in a continually changing
direction
Diode- allows an electric current to flow in one direction only
LED- a light emitting diode, a diode that gives out light when current passes
through it
LDR- a light dependent resistor, a resistor whose value of resistance can
change as the intensity of the light falling on it changes
Echo- the reflection of sound
Ohm’s law- voltage is directly proportion to current
Formulas
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Density- mass ÷ volume= gǀcm³
Speed- distance ÷ time= mǀs
Acceleration- (final speed – first speed) ÷ time taken= mǀs²
Moment of a force- force x perpendicular distance= Nm
Pressure- force ÷ area= Nǀm²
Work- force x distance= J
Power- work done ÷ time taken= W
Voltage- Current (I) x resistance (Ω)= V
kWh- number of kW x number of hours
SummaryM= D x V
D= S x T
F= P x A
V= I x R
M (mass) =g
D (distance) =m
F (force) =N
V (voltage) =V
D (density) =gǀcm³ S (speed) =mǀs
P (pressure) = Nǀm²I (current) = A
V (volume) =cm³
A (area) =m²
T (time) =s
R (resistance) =Ω