Physical Science Exam Study Guide

Uniform Motion- motion at a constant speed in a straight line

Frame of reference- stationary background used to determine motion, most common being the Earth v = velocity _ v = average velocity

v – change in velocity

Constant Speed – speed does not change Average speed- total distance covered by the amount of time, speed can change Instantaneous speed- speedometer reading

Acceleration- the change in the speed in a given amount of time, the acceleration due to gravity is 9.8 m/s2.

Force- push or pull on an object, Examples: gravity, friction

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.

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.

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.

Work- force applied over a distance W= Fd , the units for work is Joules Example: Picking up an object, going up steps.

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

Potential Energy- energy due to position Example: object on a hill, a compressed spring, a stretched rubber band

P.E. = mass X gravity acceleration X height or mgh , the units are Joules g= 9.8 m/s2

Law of Conservation of Energy- energy is never lost or created just changes forms

Pendulum is an example of energy being converted from potential to kinetic energy and then back to potential and so forth.

Heat- the energy associated with the random motion of atoms and molecules that make up a substance Measured using calories or joules.

Temperature- measure of the kinetic energy associated with the molecules Measured in Celsius, Fahrenheit, or Kelvin)

Specific Heat- the ability of a substance to absorb heat, unique to every type of substance, determined by its chemical structure

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. )

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.

Electric Force – the force that exists between two charged objects Either like charges repelling or unlike charges attracting.

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

Current – flow of electrons through a conductive material, measured in Amps

Potential Difference (voltage)- the difference in the number of charges between two points in a circuit, measured in volts

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

Ohm’s Law- I= V/R Current = Potential Difference/ Resistance

Circuit- closed path which electricity follows, a circuit consists of a source of energy, a load (electric devices), wire and a switch

Closed Circuit- the switch is closed and electrons can make a complete path

Open circuit- the switch is open and the path is not complete

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

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.

Permanent magnets- made of metals such as iron, nickel, cobalt.

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

Wave- a periodic disturbance in a material which travels from one region to another

Mechanical Waves- much travel through a material- water waves, waves on a rope, sound waves)

Electromagnetic Waves- waves that can travel through a vacuum ( radio, TV, infrared, visible light, ultraviolet, x-rays, gamma rays)

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.

Frequency- number of waves per second, measured in Hertz

Pitch- perceived frequency of a sound wave

Period= 1/frequency

Velocity of a wave = frequency time wavelength

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.

(In sound waves the amplitude is measured by how much did the object producing the sound moved. )

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

JJ. Thomson- studied gas tubes, discovered that cathode rays (used in some televisions) were made of negative particles (eventually called electrons)

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.

Bohr- “solar system” model of the atom- electrons orbiting the nucleus in definite orbits

Energy levels- equation for determining is 2n2 1st – holds 2 electrons 2nd – holds 8 electrons 3rd- holds 18 electrons 4th –holds 32 electrons

Protons- positive particles with a mass of 1 amu (atomic mass unit)

Neutrons- neutrally charges with a mass of 1 amu

Electrons- negatively charged particles with a mass of 1/1837th amu

Atomic mass- number of protons , neutrons and electrons Mass number- number of protons and neutrons only

Atomic number- number of protons (also the number of electrons in a neutral atom)

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.

Radioactivity- the breaking down of nuclei to produce other elements Discovered by Henri Becquerel.

Alpha decay- release of an alpha particle (2 protons and 2 neutrons)- reduces the atomic number by 2 and the mass number by 4

Beta decay- release of a beta particle (electron) –reduces atomic number by 1

Gamma decay- strong electromagnetic waves are produced , very dangerous Nuclear fission- splitting of an atomic nucleus

Nuclear fusion- joining to nuclei to form a single nucleus, requires extremely high temperatures Example: Hydrogen bomb

Density- mass per unit volume, solids and liquids have characteristic densities

D = m/v

Chemical reaction- the bonding of atoms to form new substances Caused by the tendency of atoms to reach stability in their outer electrons.

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)

Covalent bonds- sharing of electrons, usually occurs between nonmetals

Ionic bonds- the lost or gain of electrons, usually occurs between a metal and a nonmetal

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

Single replacement- one atom switches its bond with another element Example:

Cu + AgNO3 ---> Ag + Cu(NO3)2 Double Replacement- both atoms switch the elements they bond with Example:

KOH + H2SO4 ---> K2SO4 + H2O

Decomposition- one reactant breaks down into two or more products Example:

HgO ---> Hg + O2

Synthesis- the reactants combine to form a single product Example:

Mg + O2 ---> MgO

Solution- a mixture of two or more substances Solvent- that which does the dissolving (water) Solute- that which gets dissolved (sugar)

Solubility- measure of a substances ability to dissolve at a given temperature

Insoluble- a substance that cannot be dissolved in a given solvent (example oil does not dissolve in water, therefore it is insoluble in water)

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

Bases- bitter taste, feel slippery, (contain OH) (NaOH), turn litmus paper blue and phenolphthalein pink pH 7-14

Acids and bases conduct electricity.