<p>Physical Science Exam Study Guide</p><p>Uniform Motion- motion at a constant speed in a straight line</p><p>Frame of reference- stationary background used to determine motion, most common being the Earth v = velocity _ v = average velocity</p><p>v – change in velocity</p><p>Constant Speed – speed does not change Average speed- total distance covered by the amount of time, speed can change Instantaneous speed- speedometer reading</p><p>Acceleration- the change in the speed in a given amount of time, the acceleration due to gravity is 9.8 m/s2.</p><p>Force- push or pull on an object, Examples: gravity, friction</p><p>Newton’s 1st Law- Law of Inertia- an object at rest stays at rest, and object in motion stays in motion unless acted upon by a forces Example: A passenger in a car keeps moving even when the car stops, until the seatbelt stops them. </p><p>Newton’s 2nd Law- F = m * a , acceleration of an object depends on the force and the objects mass Example: A stronger student can accelerate a cart much faster than a small weaker student.</p><p>Newton’s 3rd Law – “Action Reaction Law”- for every action there is an equal and opposite reaction Example: A rocket is propelled forward as rocket exhaust is pushed downward.</p><p>Work- force applied over a distance W= Fd , the units for work is Joules Example: Picking up an object, going up steps. </p><p>Power- the rate of doing work P= W/t , the units are Watts The number of watts used per hour determines your electric bill. A 100 W bulb used for 5 hours uses, 20 W/h or .02 Kw/h. 1hp= 746 W Kinetic Energy- energy of motion, dependent on mass and speed K.E. = ½ m v2 , the units are Joules</p><p>Potential Energy- energy due to position Example: object on a hill, a compressed spring, a stretched rubber band</p><p>P.E. = mass X gravity acceleration X height or mgh , the units are Joules g= 9.8 m/s2</p><p>Law of Conservation of Energy- energy is never lost or created just changes forms</p><p>Pendulum is an example of energy being converted from potential to kinetic energy and then back to potential and so forth. </p><p>Heat- the energy associated with the random motion of atoms and molecules that make up a substance Measured using calories or joules. </p><p>Temperature- measure of the kinetic energy associated with the molecules Measured in Celsius, Fahrenheit, or Kelvin)</p><p>Specific Heat- the ability of a substance to absorb heat, unique to every type of substance, determined by its chemical structure</p><p>First Law of Thermodynamics- the total amount of energy never changes, energy cannot be created nor destroyed only converted Most energy in a system is lost as heat. ( The human body for example loses much of its energy as heat. )</p><p>Second Law of Thermodynamics- conversion of energy from one form to another results in some of the energy changing into heat. Heat will not flow form a cold body to a warm body. </p><p>Electric Force – the force that exists between two charged objects Either like charges repelling or unlike charges attracting.</p><p>Static Electricity- the accumulation of electric charges on an object. Can be detected by an electroscope. Electric Charges can be transferred by Friction-rubbing two objects together Conduction- direct contact, in which electrons move from one object to another Induction- a neutral object comes close to a charged object</p><p>Current – flow of electrons through a conductive material, measured in Amps</p><p>Potential Difference (voltage)- the difference in the number of charges between two points in a circuit, measured in volts</p><p>Resistance- the opposition to the flow of charges, measured in ohms - resistance is effected by the material the charges are flowing through, the thickness of the wire, and the length of the wire - thin long wires have the most resistance - short thick wires have the least resistance</p><p>Ohm’s Law- I= V/R Current = Potential Difference/ Resistance</p><p>Circuit- closed path which electricity follows, a circuit consists of a source of energy, a load (electric devices), wire and a switch</p><p>Closed Circuit- the switch is closed and electrons can make a complete path</p><p>Open circuit- the switch is open and the path is not complete</p><p>Series circuit – only one path for the electricity to flow, if one light goes out they all go out Parallel circuit- multiple paths for the electricity to flow</p><p>Electromagnet- a magnet made of a coil of wire around a iron core The more coils of the wire the strong the magnet is, increasing the current also increases the strength of the magnet.</p><p>Permanent magnets- made of metals such as iron, nickel, cobalt.</p><p>Magnetic fields- is the area around a magnet in which magnetic forces act. Magnetic domains- groups of magnetically aligned atoms, magnets can be unmagnetized if dropped or heated, and magnetized by dragging across a permanent magnet or placed in a strong electromagnetic field</p><p>Wave- a periodic disturbance in a material which travels from one region to another</p><p>Mechanical Waves- much travel through a material- water waves, waves on a rope, sound waves)</p><p>Electromagnetic Waves- waves that can travel through a vacuum ( radio, TV, infrared, visible light, ultraviolet, x-rays, gamma rays)</p><p>Speed of Light -through empty space electromagnetic waves can move at 30,000,00 m/s (3 X 106 m/s) . Through glass, water and other materials they move slower. Wavelength- distance between two crests on a transverse wave or two troughs on a transverse wave, or between two compressions on a longitudinal wave.</p><p>Frequency- number of waves per second, measured in Hertz</p><p>Pitch- perceived frequency of a sound wave</p><p>Period= 1/frequency </p><p>Velocity of a wave = frequency time wavelength</p><p>V= f * Amplitude- maximum displacement of a material from the rest position, directly related to the amount of energy the wave carries- and how loud a sound wave is.</p><p>(In sound waves the amplitude is measured by how much did the object producing the sound moved. )</p><p>Atomic Theory John Dalton- all elements composed of atoms, all atoms of the same element are alike, compounds are formed by joining the atoms of two or more elements - his statement all atoms of the same element have the same mass was later disproved by the discovery of isotopes. - he stated that the atom was a solid sphere this was later disproved by the discovery of particles</p><p>JJ. Thomson- studied gas tubes, discovered that cathode rays (used in some televisions) were made of negative particles (eventually called electrons)</p><p>Rutherford- he shot alpha particles through a sheet of gold foil, most passed straight through but some were deflected straight back, he concluded that an atom’s had a small dense positive nucleus called a nucleus is a small positive and that most of an atom was empty space.</p><p>Bohr- “solar system” model of the atom- electrons orbiting the nucleus in definite orbits</p><p>Energy levels- equation for determining is 2n2 1st – holds 2 electrons 2nd – holds 8 electrons 3rd- holds 18 electrons 4th –holds 32 electrons</p><p>Protons- positive particles with a mass of 1 amu (atomic mass unit)</p><p>Neutrons- neutrally charges with a mass of 1 amu</p><p>Electrons- negatively charged particles with a mass of 1/1837th amu</p><p>Atomic mass- number of protons , neutrons and electrons Mass number- number of protons and neutrons only</p><p>Atomic number- number of protons (also the number of electrons in a neutral atom) </p><p>Isotopes- atoms of the same element with different masses because of a change in the number of neutrons Example: Carbon – normally has 6 protons and 6 neutrons and is known as Carbon-12 However, Carbon-14 has 6 protons and 8 neutrons.</p><p>Radioactivity- the breaking down of nuclei to produce other elements Discovered by Henri Becquerel.</p><p>Alpha decay- release of an alpha particle (2 protons and 2 neutrons)- reduces the atomic number by 2 and the mass number by 4</p><p>Beta decay- release of a beta particle (electron) –reduces atomic number by 1</p><p>Gamma decay- strong electromagnetic waves are produced , very dangerous Nuclear fission- splitting of an atomic nucleus</p><p>Nuclear fusion- joining to nuclei to form a single nucleus, requires extremely high temperatures Example: Hydrogen bomb</p><p>Density- mass per unit volume, solids and liquids have characteristic densities</p><p>D = m/v</p><p>Chemical reaction- the bonding of atoms to form new substances Caused by the tendency of atoms to reach stability in their outer electrons.</p><p>Octet rule- atoms are most stable when they have 8 electrons in their outer shell (2 electrons for those elements with an atomic number less than 5)</p><p>Covalent bonds- sharing of electrons, usually occurs between nonmetals</p><p>Ionic bonds- the lost or gain of electrons, usually occurs between a metal and a nonmetal</p><p>Group/ Family- column of elements on a periodic table- have similar physical properties – determines the valence electrons for an atom Period- row in the periodic table – determines energy levels for an atom</p><p>Single replacement- one atom switches its bond with another element Example: </p><p>Cu + AgNO3 ---> Ag + Cu(NO3)2 Double Replacement- both atoms switch the elements they bond with Example:</p><p>KOH + H2SO4 ---> K2SO4 + H2O</p><p>Decomposition- one reactant breaks down into two or more products Example: </p><p>HgO ---> Hg + O2</p><p>Synthesis- the reactants combine to form a single product Example: </p><p>Mg + O2 ---> MgO</p><p>Solution- a mixture of two or more substances Solvent- that which does the dissolving (water) Solute- that which gets dissolved (sugar)</p><p>Solubility- measure of a substances ability to dissolve at a given temperature</p><p>Insoluble- a substance that cannot be dissolved in a given solvent (example oil does not dissolve in water, therefore it is insoluble in water)</p><p>Evidence of chemical change -flames, smoke - gases - precipitates (a solid that settles out of a mixture of two liquids) - changes in temperature - changes in color Acids- sour taste, contain hydrogen, react with metals (HCl), litmus red, phenolphthalein colorless pH 1-7</p><p>Bases- bitter taste, feel slippery, (contain OH) (NaOH), turn litmus paper blue and phenolphthalein pink pH 7-14</p><p>Acids and bases conduct electricity.</p>
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