Science Definitions

Biology

  • Digestion is the breaking down of food
  • Respiration is the release of energy from food
  • Excretion is the removal of waste products of chemical reactions in the body
  • An antagonistic pair is made up of two muscles that cause opposite effects
  • Sensory nerves carry messages to the central nervous system. Motor nerves carry messages away from the central nervous system.
  • Ovulation is the release of an egg from the ovary.
  • Fertilisation is the joining of the sperm and the egg to form a zygote.
  • Implantation is the attachment of the embryo to the lining of the uterus
  • Pregnancy is the time the baby spends developing in the uterus
  • Contraception is the prevention of fertilisation
  • Genetics is the study of how traits or characteristics are inherited
  • A gene is a section of DNA that can produce a protein.
  • Invertebrates are animals that do not have backbones
  • Vertebrates are animals that have backbones
  • Transpiration is the loss of water from a plant
  • The transpiration stream is a flow of water from the roots up through the stem and out of the leaves of a plant
  • Photosynthesis is the way in which green plants make food.
  • A tropism is the change in growth of a plant in response to an outside stimulus.
  • Phototropism is the way a plant changes its growth response to light.
  • Geotropism is the way in which a plant changes its growth in response to gravity.
  • Sexual reproduction involves two sex cells joining together during fertilisation.
  • A gamete is a sex cell
  • Asexual reproduction means that new individuals are formed from only one parent.
  • Pollination is the transfer of pollen from a stamen to a carpel.
  • Fertilisation is the joining of the male and female gametes to form a zygote.
  • Dispersal is the carrying of the seed as far as possible from the parent plant
  • Germination is the growth of a seed to form a new plant.
  • Ecology is the study of the relationships between plants, animals and their environments.
  • A habitat is where a plant or animal lives.
  • A population refers to all members of that particulars type of a plant or animal living in a habitat.
  • A community refers to all the plants and animals in that habitat
  • Producers are plants that make their own food.
  • Consumers are animals that get their food by eating plants or other animals
  • A food chain is a list of living things in which each one is eaten by the next one in the chain.
  • Adaptations are structures of habits that living things have which enable them to survive in their habitats.
  • Competition occurs when two of more organisms require something that is in short supply.
  • Interdependence means that living things depend on each other for survival.
  • A line transect is a rope marked at regular intervals and laid out across a habitat to estimate the number of plants present.
  • Conservation is the protection and wise management of our natural resources.
  • Pollution is any unwanted change to our environment.
  • Micro-organisms are small living things
  • A parasite is a living thing that gets its food from another living thing.
  • A saprophyte is a living thing that gets its food from dead sources.
  • Antibiotics are chemicals made by micro – organisms that kill or prevent the growth of bacteria.
  • Biotechnology is the use of living things or parts of living things to make useful products.

Chemistry

  • A mixture is made up of two or more substances mingled together but not chemically combined.
  • Elements are substances made up of only one type of atom.
  • Molecules are made up of two atoms chemically combined.
  • Compounds are made up of two or more elements chemically combined
  • Mixtures contains two or more different substances mingled together but not chemically combined.
  • Atomic number is the number of protons (or electrons) in an atom of an element.
  • Mass number is the number of protons and neutrons in an atom of an element.
  • Isotopes are atoms of the same element which have the same atomic number but different mass numbers.
  • An alloy is a mixture of metals
  • Corrosion is an undesirable process whereby a metal changes to its oxide or some other compound by combining with oxygen in air.
  • An ion is an atom which has lost or gained electrons.
  • An ionic bond is the electrical force of attraction between positive and negative ions.
  • A covalent bond consists of a pair of electrons shared between two atoms.
  • A physical change is a change in which no new substance is formed.
  • A chemical change is a change in which at least one new substance is formed.
  • A fuel is a substance that burns in oxygen to produce heat.
  • Catalysts are substances which alter the rate of a chemical reaction but are not used up themselves.
  • Electrolysis is the splitting up of a compound by passing electricity through it.
  • A solution is a mixture of a solute and a solvent.
  • A saturated solution is a solution that contains as much dissolved solute as possible at that given temperature.
  • Crystallisation is the formation of crystals by the cooling of a saturated solution.
  • Fuels are substances which burn in oxygen to produce heat energy.
  • Hydrocarbons are compounds made up of hydrogen and carbon.
  • Polymerisation is the process involving the joining together of many small molecules called monomers to form a large molecule called a polymer.

Physics

  • Length is the straight line distance between two points in space.
  • Mass is the quantity of matter in a body
  • Time is the quantity in which change happens.
  • Temperature is a measure of how hot or cold a body is.
  • Area is the amount of surface that covers a body.
  • Volume is the amount of space taken up by a body.
  • Area = length x width
  • Volume = length x width x height.
  • The density of a body is the mass of one unit of volume of a body.
  • Density = (mass / volume)
  • Speed is the distance travelled by an object in a unit of time
  • Velocity is the speed of a body and the direction in which it is moving.
  • Acceleration is the change in velocity in a unit of time.
  • Speed = distance / time.
  • Acceleration = change in velocity / time taken for the change.
  • A force gives a body at rest a velocity or makes a moving body change its velocity.
  • A force causes a mass to accelerate.
  • A change in velocity can be a change in speed or a change in direction or both.
  • Friction is a force that opposes the motion of a body when it is in contact with another
  • Lubrication is when a material is placed between surfaces of two moving bodies in contact, to reduce friction.
  • The weight of a body on the surface of the moon is the attraction between the moon and the body and this is different from the force on the earth.
  • The centre of gravity of a body is a point about which the turning effects caused by gravity are balanced. The weight of the body seems to be concentrated at this point.
  • A body is in equilibrium if its centre of gravity is not moving and the body is not turning about any point
  • A lever is a rigid body that can rotate about a fulcrum.
  • The turning effect of a force is called the moment of a force.
  • The law of the lever states that when a lever is balanced, the sum of the clockwise moments equals the sum of the anticlockwise moments.
  • Pressure is the amount of force acting on a unit area.
  • Work done = Force x distance moved in the direction of the force
  • Energy is the ability to do work
  • Power is the amount of work done in a unit of time.
  • Energy is neither created nor destroyed but can be converted from one form to another.
  • Heat is a form of energy
  • Temperature is a measure of the relative hotness or coldness of a body.
  • Increase in pressure raised the boiling point of water.
  • The heat that is needed to change the state of a substance is called latent heat.
  • Conduction is the transfer of heat through a substance without any overall movement of the substance itself.
  • Convection is the transfer of heat through liquids and gases by the mass movement of particles.
  • Radiation is the transfer of heat by means of waves that can travel through a vacuum. This is how the heat energy of the sun gets to the Earth.
  • Light is a form of energy because it is a wave and waves carry energy.
  • A luminous body creates its own light.
  • Non – luminous bodies reflect light.
  • The breaking up of white light into its different colours is called dispersion.
  • The spectrum of light is made up of seven major colours. Red orange yellow green blue indigo and violet.
  • Refraction is the bending of light as it passes from one transparent material to another.
  • Sound is a form of energy and is produced when bodies vibrate.
  • Sound needs a medium to be transmitted.
  • The speed of sound is much less than the speed of light.
  • A force something that changes the motion of a body.
  • A magnetic field is the region of space around a magnet in which certain materials and other magnets will experience a magnetic force.
  • A compass is a small magnet or a magnetised needle that is free to move in a protective case.
  • Charge exerts force on another charge.
  • Voltage = Resistance x Current or V = RI
  • Direct current is the flow of charge in only one direction around a circuit.
  • Alternating current is current that constantly changes direction.
  • A kilowatt – hour is the amount of energy provided when 1 kilowatt of power is used for one hour.
  • Cost = power rating in kW x unit cost x time in hours.
  • Electronics is the controlling of devices by directing small amounts of current around circuits.