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Transcript
Science GHSGT Review Physical Science What is Physical Science? Study of matter and energy Study of the physical world On GHSGT, physics and chemistry Speed and Velocity Speed = distance divided by time s = d/t Units of speed = m/s Velocity = speed in a given direction Example: 55 mph = speed 55 mph north = velocity Distance versus Time Graph AKA position versus time graph Straight line represents constant (uniform) speed Acceleration Acceleration = rate at which velocity changes Involves a change in speed OR direction a = (vf – vi )/ t Units of acceleration = m/s2 Example: 0 to 60 mph in 5 seconds For acceleration to occur a net (unbalanced) force must be applied Distance versus Time Graph Revisited Non-linear graph represents acceleration Parabola = constant acceleration Forces Force = a push or a pull Net Force = sum of all forces acting on an object Free-body diagram shows all forces with vector arrows Direction of force = direction of acceleration Friction is a force that always opposes motion Determining the Net Force Newton’s 1st Law of Motion An object at rest will remain at rest and an object in constant motion will remain in constant motion unless acted on by an unbalanced force. Reason for seatbelts Newton’s 2nd Law of Motion Force = mass x acceleration F = ma Newton’s 3rd Law of Motion For every action, there is an equal but opposite reaction Examples: Punch a wall, it punches back Rocket propulsion Gravity Gravity = attractive force between two objects that have mass Depends on mass and distance Effects of Mass and Distance on Gravity Momentum Momentum is mass in motion p = mv To change an object’s momentum a force must be applied Conservation of momentum states that momentum before a collision equals momentum after Energy and Work The ability to do work Work = transfer of energy by applying a force to move an object W = Fd where force and distance are in same direction Both work and energy are measured in Joules Examples of Work and No Work Hammer applies a force to move the nail in the same direction = WORK Waiter applies a force upward while the tray moves forward = NO WORK Types of Mechanical Energy Kinetic = energy of motion Potential = stored energy due to position Conservation of Energy Conservation of Energy Conversion of Energy Motor = converts electrical energy into mechanical energy Motors make fans Move which is Mechanical Generator = converts mechanical energy into electrical energy Georgia Power use a Generator to provide electricity Power Power = rate at which work is done P = W/t Measure in Watts More work, less time = More Power Less Work, Long time = Less Power Heat Energy Heat can be transferred through: Conduction = when objects touch Convection = when matter moves Radiation = in the form of waves Conductors = easily transmit energy Example: metals Insulators = do not easily transmit energy Example: gases such as air Light Light is a form of electromagnetic radiation (EM) EM spectrum shows the forms of radiation in order of increasing frequency and decreasing wavelength Color of Light We see different colors depending on the frequency of light emitted or reflected This is the reason blue flames are hotter than yellow. Blue has a higher frequency so more energy. Refraction of Light Light waves travel faster in air than in water and slower in glass than water. More dense = slower light When light enters a different medium, speed changes and it bends. Bending of light due to change in speed = REFRACTION Electricity Electrons carry a negative charge. Lost electrons = positive charge Gained electrons = negative charge REMEMBER: Like charges repel Opposites attract An object can be charged through: Friction (rubbing two objects together) Conduction (touching a charged object to an uncharged object) Induction (holding a charged object near an uncharged object) Electrical Circuits SERIES Current flows in a closed circuit Ohm’s Law V = IR Two types of circuits: Series (single path) Parallel (poly paths) PARALLEL Electromagnet One can make an electromagnet with a nail, battery, and wire When current flows through the coiled wire, the nail becomes magnetized. Electromagnetic Induction Occurs when a current is produced by moving a conducting wire through a magnetic field Fundamental Parts of the Atom Atoms are made of: Most of the mass is in the nucleus (protons & neutrons) Atomic number = number of protons Protons (+) Neutrons (neutral) Electrons (-) Silver has 47 protons Atomic mass = number of protons + neutrons Silver has 61 neutrons Periodic Table Left of zig-zag line = metals Right of zig-zag line = non-metals Along the line = metalloids Groups/Families = columns; go up and down Group number indicates # of valence electrons Rows/Periods = side to side Period number indicates # of electron shells/energy levels Groups to KNOW Group 1 = alkali metals (so reactive never found uncombined in nature) Group 2 = alkaline earth metals (less reactive than alkali but more reactive than most metals) Group 7 (sometimes 17) = halogens (very reactive non-metals) Group 8 (sometimes 18) = nobel gases (non-reactive) Acids and Bases pH determines how acidic or basic a solution is pH 1-6 = acidic pH 7 = neutral Acids dissolve to release hydrogen atoms Acid of pH 1 is much stronger than acid of pH 7 Examples: HCl strong, Citric acid weak De-ionized water pH 8-14 = basic Bases dissolve to release hydroxide ion (OH-) Base of pH 8 is much weaker than base of pH 14 Physical versus Chemical Changes Physical changes are when no new substances are formed (i.e. phase changes such as melting, freezing, boiling, condensation, evaporation, sublimation) Chemical changes occur when new substances are formed (i.e. rusting, foaming, burning) Whether physical change or chemical change, MASS IS ALWAYS CONSERVED Phase Change Diagram Radioactive Decay ALPHA DECAY •Alpha and beta decay result in transformed atom •Gamma decay results in same atom with release of energy BETA DECAY GAMMA DECAY Half-Life Half-life is the decay of some unstable isotopes at a consistent rate that can be calculated. For example: Isotope X has a half life of 100 years, if I have 50 g of Isotope X, how much will remain after 100 years? After 200 years? Good luck! You can do it!!!