Sources Of energy

solar cell a device that generates an electric current from sunlight


biomass conversion  getting energy from plant and animal materials by changing them into high-quality fuels

nuclear fission the spliting of a nucleus with large mass into two nuclei with smaller masses

chain reaction a reaction that kept going by prducts of reaction

nuclear fiction the merge of nuclie with smaller masses into a nucleus with a larger mass

hydroelectricity  the use of flowing water to generate elctricity

thermal pollution the excess of the enviroment

1.Thermal expansion: The expansion of matter when its temperature is raised.








Pressure: The force on each unit of area of a surface.







3.Melting: The change of a solid into a liquid.











4.Vaporization: The change of a liquid to a gas as molecules break free from each other.







5.Condensation: The change of a gas to a liquid as molecules break free from each other.







6.Freezing: The change of a liquid into a solid.







7. Boiling: The formation of bubbles of vapor that escape from a liquid that is being heated.











8. Evaporation: The vaporization of molecules from the surface of a liquid.

Temperature and Heat

Kinetic energy: the energy of a moving object.
















Potential energy: energy storedin an object of materials.











Temperature: the average kinetic energy of the molecules in a materials.















heat:energy that flows between objects that have differents temperatures.















Radiations: The transfer of enrgy by elecromangnetic waves.















conduction:the transfer of energy by the flow ofa liquid or gas.















Convection:the transfer of energy by the flow of a liquid or gas.















Insulation: prevents heat from flowing in out of a materials.

Chemical Changes

compound a chemical combination of two or more elements.


chemical bond a link that atoms or elctrically charged particles can form with each other.


chemical formula  a way of using letters and numbers to show how much of each element is in a substance.


ion an elctrically charged particle with unuqual numbers of protons and electrons.


molecule  a group of bonded atoms that act as a single particle.


chemical property  a way of describing how a substance changes chemically with other subtances.

exothermic  a reaction that gives off energy.

endothermic  a reaction that absob heat

Elements and Atoms

element: a substance that cannot be broken down any further into anything simpler.


atom: the smallest particle of an element taht has the same chemical properties as the element.


nucleus: a n atom's dense center, where most of its mass is.


electron: anegatively charged particle that moves around an atom's nucleus.

proton: a positively charged particle inside an atom's nucleus.

neutron: a particle with no charge inside an atom's nucleus.

atomic number: the number of protons in an atom.


metal:  a ny of a group of elements that conduct heat and elctricity, is shiny and bendable.

Physical Properties

matter: any solid, liquid or gas.


mass: amount of matter in an object


volume: the amount of space an object takes up.



density: the amount of mass in a certain volume of material.


physical property: a property that can be observed without changing the identify of a substance.


physical change: a change in size, shape, or state without forming a new substance.



solution: a mixture of one subtance dissolved in another so thatr the properties are the same throughtout.

chemical change: a change in matter that produces a new subtance with differnet properties from the original.