Physical Science Ultimate Study Guide

Name: _________________ Date: May 22nd 2014 Ms. Britt

Physical Science: Study Guide for NC Final Exam

Directions: Read the following information, highlight and underline as you read. I recommend making index cards with the information below to test your knowledge. If you create 10 index cards with study information, or a study guide you made, I will give you +20 extra credit on your Mock Final (quiz).

Warning: You cannot prepare for this kind of test in one night. Questions will ask you to apply your knowledge, not list specific facts. Preparing for the NC Final Exam will take time, effort, and practice.

Mock NC Final Exam score: ________ • List 3-­‐5 objectives you need to focus on while studying (ex: electrical circuits, naming compounds, balancing equations, half-­‐life, etc....) o o o o o

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Goal for NC Final Exam: _________

Time Management: Many students have good intentions for studying and preparing for a test, but without a plan, many will fall short of their goals. Here are some strategies for your study plan: • Set realistic goals for what you want to accomplish during the holiday break • Study during your most productive time of the day • Study for reasonable amounts of time (marathon studying is not productive) • Take breaks while studying • Be consistent – establish a routine and stick to it!

• Reward yourself for a job well done J

Active Studying: Students who actively study will learn and retain information longer. What is active studying? It can be anything that gets you to interact with the material you are studying. For ex.: • Carefully read the information and then DO something with it. Mark the important parts with a highlighter, circle them with a pen, write notes, or summarize in your own words • Create sample test questions and answer them • Find a friend and quiz each other

Basic SI Units Length: meter (m) Mass: kilogram (kg) Time: seconds (s) Energy: joules (J) Current: amps (A) Voltage: volts (V)

Speed or Velocity: meters per second (m/s) Acceleration: meters per second squared (m/s2)

Temperature: kelvin (K) Power: watts (W) Gravity: 9.8 m/s2

Work: joules (J) Force: newtons (N) Resistance: ohms Ω

• Structure and Properties of Matter • Refer to the matter diagram in your notes to refresh your memory of homogeneous and heterogeneous mixtures, solutions, suspensions, and colloids, as well as pure substances, elements and compounds.

• Pure Substances (Elements & Compounds) o An element is a substance that can’t be broken down into simpler substances § The smallest particle of an element is an atom o A compound is a combination of two or more elements in a fixed composition that can be broken down into simpler substances § Table Salt (NaCl) would be an example of a compound – fixed composition – as well as water (H2O) o A colloid contains particles that are intermediate in size between a solution and a suspension • Mixtures o Properties of a mixture can vary because the composition of a mixture is not fixed, like salsa – you don’t always have 5 tomatoes to 4 green peppers – it varies • Heterogeneous: parts of the mixture are noticeably different from one another; like sand on the beach filled with seashells – consists of two or more substances and it non-­‐uniform o A suspension is a heterogeneous mixture that separates into layers over time § Larger particles scatters light (can’t see through); when filtered, substances separate; settles into layers over time (yoohoo chocolate drink) • Homogeneous: The substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another ; like swimming pool water or sweet tea; you can’t tell the chlorine from the water or the sugar dissolved in the tea – is uniform and the different components cannot be seen o A solution is a homogeneous mixture in which substances dissolve § Light passes through it; does not settle over time; when filtered, none of the substance in the solution are trapped (coffee, sweet tea) • A colloid contains some particles that are intermediate in size o Doesn’t separate into layers over time; cannot use a filter to separate its parts; scatters light (fog)

• A physical property is any characteristic of a material that can be observed or measured without changing the composition of the substances in the material o Viscosity, conductivity, malleability, hardness, melting point, boiling point, and density are examples of physical properties o Viscosity is the tendency of a liquid to keep from flowing – its resistance to flowing o Conductivity is a material’s ability to allow heat to flow § Metals are good conductors o Malleability is the ability of a solid to be hammered without shattering; solids that shatter when struck are brittle o Hardness: You can compare hardness by seeing which material will scratch another in a scratch test – hardest known material? Diamond o Melting point: the temp. at which a substance changes from a solid to a liquid o Boiling point: the temp. at which a substance boils (from liquid to gas or vapor)

o Density: The ratio of the mass of a substance to its volume D = m/v § Matter is anything that has mass § Volume is how much space the object occupies § Density tells us more about what the object/subject actually is o Luster: Refers to how “shiny” the substance is

o A physical change occurs when some of the properties in a material change, but the substances in the material remain the same § Examples: heating butter in a pan; slicing a tomato; crumping a piece of paper; ice melting

o A chemical change is any ability to produce a change in the composition of matter

§ Can only be observed when substances in a sample of matter are changing into different substances • 3 common types of evidence for a chemical change: o Change in color o Production of gas o Formation of precipitate § A precipitate is any solid that forms and separates from a liquid mixture (cottage cheese) § Occurs when a substance reacts and forms one or more new substances § Examples: A cake bakes in the oven; leaves on a tree change color; food is digested in your stomach • Flammability: A material’s ability to burn in the presence of oxygen • Reactivity: Describes how readily a substance combines chemically with other substances • Refer to the phase change diagram in your notes and study the different phases of matter in the solid, liquid, and gas form § Melting: solid èliquid § Vaporization: liquid è gas § Freezing: liquid èsolid § Condensation: gas è liquid § Sublimation: solid ègas • Solubility is the max amount of solute that will dissolve in a certain amount of solvent @ a given temperature o Solute: substance dissolved o Solvent: does the dissolving § Factors that affect the rate of dissolving include: surface area, stirring, and temp. § Example: H2O • Increase SA by dividing it into smaller pieces • Stirring mixture (allows more collisions) • Increasing the temp. of the solvent § Solutions are described as saturated, unsaturated, or supersaturated depending on the amount of solute § Saturated solution contains as much solute as the solvent can hold (filled) § Unsaturated solution has less than the max amt. of solute than can be dissolved

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§ Supersaturated solution contains more solute than it can normally hold @ a given temp. o Solubility curves are used to show how the solubility of a substance changes with temperature o Studying the curve to the right and see if you can read the curves o To read the solubility curves: 1. Find the line for the substance 2. The amount that dissolves @ a given temp. is on the y-­‐axis 3. The solubility of which solution decreases as the temp. increases?

Ce2(SO4)3 4. At what temperature would 40g of KCl dissolve? About 43 °C • Remember, “like dissolves like”; in general, the solubility increase as the temperature of the solvent increases; increasing the pressure on a gas increases its solubility in a liquid Concentration is the amount of solute dissolved in a specified amount of solution To dilute is to make a solution thinner or weaker by adding more solvent (usually water) to it Mass: the quantity of matter in an object or sample Volume: the amount of space taken up by an object Density: the ratio of an object’s mass to its volume (D = m/v)

Atomic Structure: Don’t worry about remembering the people & the models specifically... those types of questions will not be on your test, but it may help you better understand how the structure of the atom is understood today Protons, neutrons, & electrons Proton: positively charged subatomic particle that is found in the nucleus (Rutherford) Electron: negatively charged subatomic particle that is found in the space outside the nucleus • Neutron: A neutral subatomic particle found in the nucleus of an atom; it’s mass is almost exactly = to that of a proton

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Protons & neutrons have almost the same mass (1 amu each) It would take about 2,000 electrons to = the mass of 1 proton Atomic # = # of protons (if neutral, # of e-­‐) Mass # = sum of protons & neutrons in the nucleus of the atom # of neutrons = mass # -­‐ atomic number Isotopes are atoms of the same element that have different numbers of neutrons & different mass numbers (same atomic # but different mass numbers) o Carbon-­‐12: has 6 protons and 6 neutrons # of protons doesn’t change – if the o Carbon-­‐13: has 6 protons and 7 neutrons atomic # changes, it’s a totally o Carbon-­‐14: has 6 protons and 8 neutrons different element!

• In Bohr’s model, electrons move with constant speed in fixed orbitals around the nucleus (like planets around the sun) o Energy levels are the possible energies that e-­‐ in an atom can have o An e-­‐ in an atom can move from one energy level to another when the atom gains or loses energy o When the highest occupied energy level of an atom is filled with e-­‐, the atom is stable and not likely to react (Noble gases have stable electron configurations, 8 VEs) o An electron cloud is a visual model of the most likely locations for e-­‐ in an atom § In the 1st ring or energy level, there can be maximum of 2 electrons § In the 2nd ring or EL, there can be a maximum of 8 electrons § In the 3rd ring or EL, there can be a maximum of 18 electrons o To study how to draw and ID bohr models, look in your notes & see the examples below

• An ion is an atom that has gained or lost electrons (has a charge) o Cation: positive ion (lost electrons) *Metals are cations, they lose e-­‐) o Anion: negative ion (gained electrons) *Nonmetals are anions, they gain e-­‐) • Isotopes of an element have the same atomic # but different mass #s and different # of neutrons *See above notes • An electron dot diagram is a model of an atom in which each dot represents a valence electron • Bonding: Ionic, Covalent, Metallic • Valence electrons determine the bonding between atoms • A valence electron is an e-­‐ located in the outmost cloud • Look at the group # of family to figure out how many VEs an atom has • The Octet Rule states that atoms generally want to gain, lose, or share e-­‐ in order to have eight VEs & to be most stable (happy) • A chemical bond is the force that holds atoms or ions together as a unit o Elements that do not have complete sets of VEs tend to react o Some electrons achieve stability through the transfer of e-­‐ between atoms (ionic bonding)

o In the diagram above, Na forms an ionic bond with Cl by giving Cl an e-­‐. Therefore, Cl has 8 VEs and is happy J Na also has a full outer shell. Since Na (a metal, lost an e-­‐, it becomes positive (cation) and since Cl gained an e-­‐, it becomes negative (anion)

o An ionic bond is the force that holds cations and anions together (e-­‐ are transferred) § Ionic bonds form between a nonmetal & a metal § Metals (cations) & Nonmetals (anions) o A positive ion has lost electrons and a negative ion has gained electrons o Ionization energy: the amount of energy use to remove an electron from an atom § Transitional metals can form more than 1 type of ion • When an element can form an ion in more than one way, like Copper (Cu+ or Cu2+), it always contains a roman numeral that indicates the ion charge o Cu+ is named copper (I) o Cu 2+ is named copper (II) o A covalent bond is a chemical bond between two nonmetals in which the atoms share a pair of valence electrons (uses prefixes) § Is the following an ionic or covalent bond?

• CaCl2 __________ • CO2 __________ • H2O __________

• When writing chemical formulas, follow the following rules: o Ionic: write the name and add “-­‐ide” suffix o Covalent: check subscripts, write prefixes, add “-­‐ide” suffix o Transition metal: check oxidation # and roman numerals

o A metallic bond is the attraction between metal cation and the shared electrons that surround it (between a metal & a metal) o Metal alloys are created through metallic bonding; An alloy is a mixture of two or more elements, at least one of which is a metal (examples: brass and steel)

• Chemical Equations: Know how to balance & classify o The substances that undergo change are called reactants o The new substances formed as a result of that change are called products • The law of conservation of mass states that mass is neither created nor destroyed in a chemical rxn o The mass of the products is always equal to the mass of the reactants o In order to show that mass is conserved during a reaction, a chemical equation must be balanced • To balance a chemical equation: o We change the coefficient (big # in front) o We do not change the subscripts (little #s at the bottom) o Coefficients can only go at the front of an equation – not the middle! o Multiply the coefficient by the subscript to get the # of atoms o Coefficient is distributed to each element in the compound (separated by plus sign)

• Types of chemical reactions include: synthesis, decomposition, single-­‐replacement, and double-­‐ replacement • A synthesis reaction is a rxn in which two or more substances react to form a single substance o A + B è AB o 2Na + Cl2 è 2NaCl • A decomposition reaction is a reaction in which a compound breaks down into two or more simpler substances o AB è A + B o 2H2O è 2H2 + O2 • A single-­‐replacement reaction is one in which one element takes the place of another element in a compound o A + BC è B + AC • A double-­‐replacement is one in which two different compounds exchange positive ions and form two new compounds o AB + CD è AD + CB • A combustion reaction is one in which a substance reacts rapidly with oxygen, often producing heat and light

• Acids & Bases and pH Scale • pH is a measure of how acidic or basic a solution is; ranges from 0-­‐14 o Acidic solutions have a pH value below 7 (HCl is a popular acid) o Basic solutions have a pH value above 7 (NaOH is a popular base) o 7 is neutral (like water) o Acids: A solution that has an excess of H+ ions; the more H+ ions, the more acidic the solution § Acids taste sour, conducts electricity, corrosive, turns blue litmus paper red § Acetic acid: vinegar; citric acid: lemons; sulfuric acid: fertilizer § Has a pH less than 7 o Bases: A compound that produces hydroxide ions (OH-­‐) when dissolved in water § A solution that has an excess of OH-­‐ ions § Bases feel slipper, taste bitter, turns red litmus paper blue § Has a pH greater than 7 • A reaction between an acid and a base is called neutralization o In general: Acid + Base è Salt + Water o All neutralization reactions are double replacement

• Radioactive decay is the process in which an unstable atomic nucleus emits charged partciles and energy o Any atom containing an unstable nucleus is called a radioisotope o Unlike stable isotopes like carbon-­‐12, radioisotopes spontaneously change into isotopes over time o Nuclear radiation is charged particles and energy that are emitted from the nuclei of radioisotopes: alpha particles, beta particles, and gamma rays § An alpha particle is a positively charged particle make up of 2 protons & 2 neutrons (the same as helium) • LEAST penetrating type of radiation; can be stopped by paper or clothing • Alpha decay reduces the mass of an atom by 4 and the atomic # by 2 § A beta particle is a fast moving e-­‐ emitted by an unstable nucleus; has a negative charge (atomic # of -­‐1 and mass # of 0) • Have greater range of penetration than alpha particles, but less than gamma rays § A gamma ray is the most penetrating form of radiation; it is a penetrating ray of energy emitted by an unstable nucleus (has no mass & no charge) HULK • Takes several centimeters of lead or concrete to stop gamma rays o A nuclear decay rate describes how fast nuclear changes take place in a radioactive substance; every radioisotope decays at a specific rate expressed as a half-­‐life o A half-­‐life is the time required for one half of a sample of a radioisotope to decay

• Nuclear fission: the splitting of an atomic nucleus into two smaller pieces o Tremendous amounts of energy can be produced from very small amounts of mass o Critical mass is the smallest possible mass of a fissionable material that can sustain a chain reaction o Nuclear power plants generates about 20% of the electricity in the US § In a power plant, controlled fission of uranium-­‐235 occurs • Nuclear fusion: the process in which the nuclei of two atoms combine to form a larger nucleus (the sun is powered by the fusion of hydrogen and helium)

• Periodic Table: You must have an understanding of how to read the periodic table (it’s like reading a map) so that you can do well on the chemistry portion of the exam. I recommend printing off blank periodic tables and practice writing the oxidation #, group #, period #, metals, nonmetals, and metalloids, etc. o The vertical columns on the PTE are called groups or families (numbered 1-­‐18) § Elements in the same group have the same # of valence e-­‐ § Elements in each group have similar properties

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o The horizontal rows on the PTE are called periods § The period # tells you the number of rings or energy levels • Elements in period 1 have 1 energy level (ring), period 2 have 2 energy levels (rings), etc.

Motion & Forces: Scalar & Vector Quantities o Scalar: quantities are fully describe by magnitude (a number) alone (ex: 27 meters) o Vector: quantities are fully described by magnitude AND direction (ex: 4 miles, North) § Think about Vector from Despicable Me “committing crimes with both magnitude and direction” To describe motion, you must state the following: o The direction of movement o How fast it is moving o Its location at a certain time Position describes your location (where you are) – must use reference points to help specify your position A frame of reference is a reference point combined with a set of directions A frame of reference is a system of objects the are not moving with respect to one another; it’s relative – meaning it depends on one’s perspective Distance is the total length of the path taken in going from the initial (starting) position to the final position (it’s scalar) *The SI unit is the meter (m) Displacement is the direction from the starting point and the length of a straight line from the starting point to the ending point (it’s vector) Speed is the ratio of the distance an object moves to the amount of time the object moves o The SI unit for speed is (m/s) § Average speed: the total distance traveled divided by the time it takes to travel that distance (total distance/total time) § Instantaneous speed: the rate at which an object is moving at a given time When graphing motion, the slope of a line is speed (distance-­‐time graph) Constant speed is speed that doesn’t change Acceleration is the rate at which velocity changes o A = change in velocity/total time Velocity is vector and speed is scalar – velocity gives a direction, speed does not •

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A free fall is an example of acceleration due to change in speed • A free fall is a movement of an object toward Earth solely because of gravity •

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Obejcts falling near Earth’s surface accelerate downward at a rate of 9.8 m/s2

• Acceleration can be both changing speed and direction • Inertia: tendency of a still object to stay still or a moving object to keep moving unless acted on by an unbalanced force o Mass is a measure of the inertia of an object and how much matter the object consists of o Weight is a measure of the force of gravity acting on an object (can change depending on the gravitation force -­‐-­‐-­‐ your weight on Earth & on the moon is NOT the same) • Force: a push or a pull that acts on an object (measuring in newtons); can accelerate a moving object by changing its speed, its direction, or both (f = ma) • Net force: the overall force acting on an object after all the forces are combined • Gravity: A force that acts between any two masses; is an attractive force that pulls objects together o Newton’s three laws of motion 1. An object at rest will remain at rest, an object in motion will remain in motion with the same speed and direction, unless acted upon by an unbalanced force (law of inertia) 2. The acceleration of an object is equal to the net force acting on it divided by the object’s mass 3. Whenever 1 object exerts a force on a 2nd object, the 2nd object exerts an equal and opposite force on the 1st object (for every action there is an equal and opposite reaction) • Friction is a force that opposed the motion of objects that touch as they move past each other o 4 main types: static, sliding, rolling, fluid § Static: friction force that acts on objects that are not moving § Sliding: friction force that opposes the motion of an object as it slides over a surface § Rolling: friction force that acts on rolling objects § Fluid: friction force that oppose motion of an object through a fluid o The more friction present, the greater force that needs to be applied o As an object moves farther away from the center of earth, the gravitational pull of the earth decreases o As an object free falls, it accelerates downward to Earth at a rate of 9.8 m/s2 • Momentum can be defined as “mass in motion” – All objects have mass; so if an object is moving, then it has momentum – it has mass in motion o Momentum depends on 2 variables: how much stuff is moving and how fast is the stuff moving § p = m x v § (momentum = mass x velocity)

• Energy is the ability to do work; energy is transferred by a force moving an object through a distance o Work is a transfer of energy

• Work is done on an object; energy is transferred to that object (w = fd) o In order for work to be done on an object; some of the force applied to the object must act in the same direction that the object moves § Example: The hamster to the right is NOT doing work on the barbell because the barbell is NOT moving (it’s stationary) • When the little hamster was raising the barbell up, and his force was applied upward, he WAS doing work on the barbell o Both work and energy are measured in joules (J) o The main forms of energy are kinetic energy and potential energy § Kinetic energy is energy of motion (KE = ½mv2) § Potential energy is energy that is stored (PE = mgh) • Gravitational potential energy depends on an object’s height and mass § Increases when an object is raised to a higher level or the mass is greater o Elastic potential energy is stretch or compressed (guitar string) • Mechanical energy is the energy associated with the motion and position of energy objects; it is the sum of an object’s PE and KE • Thermal energy is the total PE and KE of all the microscopic particles in an object o When an object’s atoms move faster, its TE increases and the object becomes warmer § TE depends on a material’s temperature, mass, and phase (solid, liquid, gas) • Heat is a transfer of TE from one object to another because of a temp. difference o Heat flows spontaneously from hot objects to cold objects o Heat is measured in joules (J) o The law of conservation of energy states that energy can’t be created nor destroyed; it’s constantly moving around the universe in and out of different matter o The total energy after a transformation is equal to the total energy before the transformation • Heat is transferred in three different ways: conduction, convection, and radiation o Conduction is the transfer of TE with no overall transfer of matter (touching) o A thermal conductor allows heat to pass through easily (metal, like copper) o A thermal insulator is a material that doesn’t allow heat to pass through (wool jacket or wooden spoon) o Convection is the transfer of TE when particles of a fliud move from one place to another (convection current in an oven) o Radiation is a transfer of energy by waves moving through space (like the sun) § In picture to the right: • X: Convection (fluid) • Y: Conduction (touching) • Z: Radiation (waves through space)

• Simple Machines • The rate at which work is done is called power; machines help people increase power and makes work easier to do (power = work/time) power is measured in watts § The force you exert on a machine (effort) is referred to as the input force § The force produced by the machine (load) is called the output force • Friction (force that opposed motion) is always present, therefore, NO machine is 100% efficient (Link for review: http://quizlet.com/_pbkst o The percentage of work input that becomes work output is the efficiency of the machine o The mechanical advantage of a machine is the # of times that the machine increases an input force (AMA = output force/input force) o The ideal mechanical advantage of a machine (IMA) is its mechanical advantage in the absence of friction (in an ideal or perfect world...) (IMA = input distance/output distance) o Efficiency = work output / work input x 100 (always expressed as a percentage)

• 6 Types of Simple Machines: 1. Lever: a rigid bar that is free to move around a fixed point (fulcrum) (seesaw) a. Wheel & Axle: consists of two disks/cylinders, each with a different radius (steering wheel in your car) b. Pulley: consists of a rope that fits into a groove in a wheel (crane) 2. Inclined Plane: a slanted surface along which a force moves an object to a different elevation (ramp) a. Wedge: a v-­‐shaped object whose sides are 2 inclined planes sloped toward each other (blade of an ax) b. Screw: an inclined plane wrapped around a cylinder (bottle cap)

• Waves and Electromagnetic Spectrum • A mechanical wave is a disturbance in matter that carries energy from one place to another • A mechanical wave is created when a source causes a vibration to travel through a medium o Energy is the ability to do work o Mechanical waves need a medium to travel through (can be a solid, liquid, or gas) • The wave to the right is called a transverse wave because the medium vibrates at right angles (perpendicular) to the direction in which the wave travels o A: crest (highest point on a wave) o B: trough (lowest point on a wave) o C: amplitude (max. displacement of wave from resting position) o D: wave length: measured from trough to trough or crest to crest § As frequency increases, wavelength decreases (inversely proportional) • In a longitudinal wave, the vibration of the medium is parallel to the direction the wave travels (to start a LW, you add energy via pushing or pulling) o *Think about a slinky* o Areas where the coils/springs are close together are called compressions o Areas where the coils/springs are farther apart are called rarefactions § G: wavelength § H: compression § I: rarefaction • A surface wave is a wave that travels along a surface separating two media o Ocean waves travel between water & air (carries energy from left to right) o A bobber in the ocean moves up & down (perpendicular) and left to right (parallel) **most waves do not transfer matter from one place to another**

• Describing Waves: o The time required for one complete cycle, a complete motion that returns to its starting point, is called the period § A frequency is the # of complete cycles (periods) in a give time (measured in hertz)

• The 1st wave in the picture to the right has a greater frequency, but a shorter wavelength (there are more complete cycles or periods – more zigzags in the same amount of time) § Wavelength is the distance between a point on one wave & the same point on the next cycle of the wave (measured in meters) § Wave speed = wavelength x frequency • Behavior of Waves: o Reflection: Occurs when a wave bounces off a surface that it can’t pass through o Refraction: The bending of a wave as it enters a new medium at an angle o Diffraction: The bending of a wave as it moves around an obstacle or passes through a narrow opening o Interference: Occurs when two or more waves overlap and combine together § Constructive interference: Occurs when 2 or more waves combine to produce a wave with a larger displacement § Destructive interference: Occurs when 2 or more waves combine to produce a wave with a smaller displacement • Sound waves are longitudinal waves – compressions & rarefactions that travel thorugh a medium (SONAR – used to determine distance to an object under water) • Electromagnetic waves can travel through empty space (NO MEDIUM REQUIRED) o Electromagnetic waves are transverse waves consisting of changing electric fields and changing magnetic fields o The transfer of energy by electromagnetic waves traveling through matter or across space is called electromagnetic radiation § The full range of frequencies of electromagnetic radiation is called the electromagnetic spectrum • Radio waves have the longest wavelength, but the lowest frequency

• Gamma rays have the shortest wavelength, but the highest frequency & the most energy (made the Hulk!)

• Visible light is the only part of the spectrum we can see (ROYGBIV)

• Static & Current Electricity o An excess (too many) or shortage of electrons produces a net electric charge § The SI unit of electric charge if the coulomb (C) § Like charges repel, opposite charges attract • Electric force (force of attraction or repulsion) depends on charge and distance o The electric field around a positive charge points outward; the electric field around a negative charge points inward o Static electricity: Build up of electrical charges on the surface of a material § Can be transferred by friction (rubbing a balloon against your hair), contact (touching a Van de Graaf generator), or induction (rubbing your socks on the carpet *friction* then going to touch a metal doorknob but not quite touching it, still causing the e-­‐ to move away from your negatively charged hand and possibly getting shocked through static discharge) • The law of conservation of charge states that the total charge in a system remains constant (the same) o Current electricity: The continuous flow of electric charge; measured in amps § Direct current (DC) – charge can only flow in one direction § Alternating current (AC) – charge regularly reverses direction o Conductor: allows charge to flow (metal) o Insulator: charge can’t flow easily (rubber) § Electrons flow more easily through a thicker wire than a thin wire • According to Ohm’s Law, V = I x R (volts = current x resistance) o A material’s thickness (diameter or width), length, and distance affect its resistance (think about our milkshake analogy) o An electric circuit is a complete path through which charge can flow o Series circuit: charge only has one path which it can flow § One light goes out, they all go out o Parallel circuit: circuit with two or more paths through which charge can flow § One light goes out, the rest keep shining

• Magnetism o A magnet is any object that has a magnetic field o A magnetic force is the force a magnet exerts on another magnet or on moving charges o Contains a north and south pole o Opposite poles attract o Like poles repel • A magnetic field surrounds a magnet and can exert magnetic forces (strongest near the poles) o Will either attract or repel another magnet § Magnetic lines of force always begin on the north pole of a magnet and end on the south pole of the magnet

• An electromagnetic is a magnet that runs on electricity (temporary) o The strength of an electromagnet can easily be changed by changing the amount of current that flows through it § An electromagnet is created when electricity flows through a conductor and the magnetic field goes around it § Electromagnets are built by wrapping many coils of wire (solenoid) around a ferromagnetic core (almost always iron) o The moment the switch on an electromagnet is turned off, the solenoid is demagnetized (cuts off) o The strength of the electromagnet depends on how many times the wire (solenoid) is wrapped around the core (more turns = more strength) o Electromagnetics are usually considered better than permanent magnets because electromagnets can easily be shut off & its strength is easily controlled § Electromagnets are used in speakers, power door locks, etc.

• A generator is a device that moves a magnet near a wire to create a steady flow of e-­‐ o The pressure pushing the e-­‐ is called the voltage and is measured in volts o Converts mechanical energy into electrical energy • An electric motor is a device that uses an electromagnet to turn an axle o Converts electrical energy into mechanical energy

Best of luck studying! J If you need anything, please reach out: Email: bbritt@sampson.k12.nc.us Twitter: @msbritt123