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O.G.T. SCIENCE TEST: QUICK STUDY GUIDE Chemistry Matter Two main families of matter: MIXTURES and SUBSTANCES MIXTURES can be separated by physical means HOMOGENEOUS- all parts are equal and looks the same (Kool-Aid) HETEROGENEOUS- parts are in different proportions and can be easily identified (chocolate chip ice cream) SUBSTANCES cannot be separated by physical means ELEMENTS- subs that are made of one kind of matter COMPOUNDS- 2 or more elements bonded together Atomic Structure Protons- positive particles in the nucleus Neutrons- neutral particles in the nucleus Electrons- negative particles in energy levels Nucleus- center of atom; contains the atoms mass Valence electrons- electrons on last energy level of any atom (Magic number is 8) Energy levels- fixed paths or orbits surrounding nucleus where electrons are found Notable Periodic Families Group 1- Alkali Metals Group 2- Alkaline Earth Metals Groups 3-13ish – Transition metals Group 7- Halogens Group 8- Noble Gases Physical vs. Chemical Properties/Changes Physical- reversible; does not change identity or make up of matter (reversible) Chemical- creates a new substance; starting materials are completely different from ending materials (not reversible) States of matter Solid-molecules vibrate but have a fixed position (definite volume and shape) Liquid –molecules can flow easily past one another (def. volume; take shape of container) Gas – molecules move freely (no def. shape or volume) Plasma- extremely high energy state of matter (no def shape or volume) Periodic Table Basics Atomic number= number of protons of an element (whole number) Atomic mass= protons + neutrons (average mass of isotopes; the one with the decimal) Atomic symbol= used to represent an element Atomic name= name given to element Isotope= same element with different number of neutrons Phase changes SL= melting LG = evaporation LS= freezing GL= condensation SG= sublimation GS = deposition Molecules speed up as they go from a solid to a liquid to a gas; they slow down if they move from a gas to a liquid to a solid Periodic Table Trends Group/Family- Vertical columns on the periodic table Periods- horizontal rows on the PT Group number (except for transition metals) represent numbers of valence electrons for a certain family Oxidation number- number of gained or lost valence electrons for each family Positive #- metals; they give away Ve’s to be chemically stable Negative #- nonmetals; they receive Ve’s to be chemically stable Noble gases- chemically stable- have all 8 valence e’s except He (happy with its 2!) Bonding Ionic bonding- transferring of valence electrons from a metal to a non metal (i.e. Na to Cl); oxidation number assigned as Ve’s are lost or gained Covalent bonding- complete sharing of valence electrons between two non metals (i.e. S and O); no oxidation numbers assigned Law of Conservation of Energy/Mass- Energy or mass cannot be created or destroyed it simply changes forms Mass of reactants= mass of products (sub energy for mass) DENSITY Signs of Chem Reaction Bubbles (gas formation) Light/heat Change in color Change in odor Formation of a solid Acids/Bases Acids- low pH; sour taste pH range 6.9-0 Bases- high pH; bitter taste pH range 7.1-14 pH scale 0-14; 7 is neutral water is neutral Lewis Dot Diagram Valence electron config. density = mass/volume Substances that are MORE dense SINK. Substances that are LESS dense RISE. Bohr Model O.G.T. SCIENCE TEST: QUICK STUDY GUIDE Physics Forces and Motion (Newton’s Laws) Force = An action exerted on a body in order to change that body’s state of rest or motion. Examples of Force: Push, Pull, Gravity, friction. Motion = An objects change in position relative to a reference point. Speed = An objects distance divided by the time it takes to move that distance. Speed can be measured as an average speed or an instantaneous speed. Velocity = speed with direction. Acceleration = The change in an objects speed over time. Newton’s 1st Law: an object in motion stays in motion and an object at rest stays at rest unless acted on by an outside force. Also referred to as Inertia. Newton’s 2nd Law: F = ma (Force = mass X acceleration) Newton’s 3rd Law: for every action force there is an equal and opposite reaction force. Net Force = The sum of all forces acting on an object. If the net force is zero then forces are balanced. Friction = A force that opposes motion between two surfaces that are in contact. Friction will slow an object down. Types of friction are static, sliding, rolling, and air resistance. Gravity: Under ideal conditions, objects fall to the ground at the same rate; it does not matter if one is heavier than the other. The constant for the acceleration of gravity is 9.8m/s/s. Waves Wave = A disturbance that carries energy through matter or space. Mechanical wave = A wave that requires a medium through which to travel. (ex. air or water or glass) Medium = A physical environment in which phenomena occur. Electromagnetic wave = A wave that consists of oscillating (alternating back and forth) electric and magnetic fields. Transverse wave = A wave in which particles in the medium move perpendicular to the motion of the wave. Ex. Waves on the ocean. Longitudinal wave = A wave in which particles of the medium vibrate parallel to the motion of the wave. Ex. the compression and expansion on an accordion. Parts of a wave Crest – The highest point of a wave Trough – The lowest point of a wave Wavelength – The distance from any point on a wave to an identical point on the next wave. Amplitude – The distance that particles vibrate from the resting point. ENERGY Energy = The capacity to do work. Work = The force placed on an object to move it a distance or (f X d). It is expressed in the unit joules. Power = The amount of time it takes to do work or (w/t). It is expressed in watts. potential energy – an object’s stored energy. It is an energy of position. The higher an object the more potential energy it would have. The formula for calculating potential energy is PE = mgh (mass X gravitational constant X height) kinetic energy – an object’s energy while in motion (the faster it moves, the more kinetic energy it has). The formula for calculating kinetic energy is KE = ½ mv2 (one half the mass X velocity squared) Forms of potential and kinetic energy – mechanical, chemical, heat (thermal), light (radiant), electrical, sound, nuclear. The law of conservation of energy states that energy cannot be created or destroyed but just changes from one form to another. Nuclear energy is produced through the fission (splitting) of atoms or the fusion (combining) of atoms. The sun produces energy by fusing hydrogen into helium. Radioactive Decay = The disintegration of an unstable atomic nucleus. Half Life = The time required for half of a sample of radioactive substance to break down by radioactive decay. Example if Carbon’s half life is 5730 years and I have a 100 g sample then there would be 50 g left after 5730yr. Wave Interactions – Sound – Light Reflection – The bouncing back of a ray of light, sound, or heat when it hits a surface it cannot go through. Refraction – The bending of a wave as it passes between two substances in which the speed differs. Diffraction – A change in the direction of a wave when hits an obstacle, edge, or opening. Interference – The combination of two or more waves that results in a single wave. Constructive interference – two waves produce a single wave that is equal to the sum of the two waves. Destructive interference – two waves produce a single wave that is equal to the difference between the two original waves. Resonance – occurs when two objects vibrate at the same frequency. It is used to amplify the sound of instruments. SONAR – SOund Navigation And Ranging . It uses acoustic signals and echoes to determine the location of objects. Electromagnetic spectrum – Consists of waves at all possible frequencies. Radio wave, microwaves, infared waves, visible light waves, ultraviolet waves, xrays, and gamma rays. RADAR – RAdio Detection And Ranging. Uses reflected radio waves to determine both the velocity and location of objects.