# Middle School Science Praxis Prep

matter anything that has mass, made of atoms and molecules
physical change of matter caused by motion, temperature, pressure – substance stays the same
chemical change of matter happen on a molecular level – substance changed
Conservation of Mass (Lavoisier) matter is neither created or destroyed
Conservation of Energy (Mayer) aka First Law of Thermodynamics – energy is neither created or destroyed
Law of Conservation of Mass-Energy (Einstein) the total amount of mass and energy in the universe is constant
kinetic energy energy of moving objects; energy in use
potential energy stored energy; it is energy that has the potential to do work
oxidation reduction reactions transfer energy between molecules in the form of electrons – the molecule that loses an electron is oxidized, molecule that gains electron is reduced
endergonic reactions store energy within a molecule because the reactants have less free energy than the products – require energy input
exergonic reactons release energy, laving reactants with more free energy than the products
heat (amount of energy in a system) total energy in a substance – kinetic energy of molecules AND potential energy of molecules
temperature (measure of the average moleculation motions in system) average kinetic energy of the molecules of the substance
conduction materials in physical contact – energy transferred trough collisions of their particles, Kinetic Theory of Matter
convection movement of thermal energy from one area to another in a liquid or gas
radiation warm or hot matter emits electromagnetic radiation – especially infrared – that is then absorbed by an object at a distance, absorption heats the second object
calorie/joules 1 cal = 4.186 J
BTU amount of energy necessary to raise temperature of 1lb water to 1 degree fahrenheit
First Law of Thermodynamics energy can be transferred from one sysem to another – energy cannot be created or destroyed – total amount of energy in universe is constant
Second Law of Thermodynamics heat cannot transfer from colder to hotter body – all natural processes that involve energy must have one direction, natural processes are irreversible, disorder/randomness of isolated system always increases with time
atom smallest unit of element that displays all of that elements characteristics
protons positively charged particles located within the atomic nucleus
neutrons neutral particles located within the atomic nucleus
electrons negatively charged particles orbiting around nucleus
atomic number protons in an atom
atomoic mass protons and neutrons combined
first electron shell one orbital; two electrons
second electron shell four orbitals; eight electrons
third electron shell four orbitals max; eight electrons
fourth electron shell max nine orbitals; eighteen electrons

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