Eight Grade Review Part One

Matter Matter - anything that has mass and takes up space. Can be classified as elements, compounds, or mixtures Made up of atoms Exists as solids, liquids, gases, or plasma

Matter continued... Atom - building block of matter. Always in motion. Atoms of the same element are alike. Electrons are negative Protons are positive. Compounds are two or more elements chemically combined. Mixtures are physically combined.

Acidity and pH scales Acids release hydrogen ions. H+ Bases release hydroxide ions. OH- pH ranges from is neutral are acids; 0 is strongest are bases; 14 is strongest Equal strength acids and bases combine to form salt and water; this is called neutralization.

Periodic Table Periodic table is arranged in order of atomic numbers. Atomic numbers refer to number of protons. Electrons always equal number of protons. Atomic mass is neutrons plus protons. Family/group/column are formed through common properties. Rows/periods are formed through equal number of electrons orbit levels

Periodic Table

More on the table... The staircase separates metals and non- metals. Metals are on the left. Non-metals are on the right. Elements touching the staircase are called metalloids and share characteristics of both. Atoms lose/gain valence electrons to become stable. How many valence electrons does the noble gas family have?

Bonding Covalent bonding is when elements share electrons. Ionic bonding is when elements transfer (lose or gain) electrons. If the element has eight valence electrons it can not bond with another element. Polyatomic bonding is when both types of bonding have occurred. (ex: water)

What type of bonding is this?

Balancing Equations How many atoms are in 2N 2 O 3 ? Law of conservation of matter states matter can never be destroyed (what goes in…comes out) Reactants are always on the left and the arrow always points to the product. Balance this equation: H 2 + O > H 2 O

Mixture types Homogenous = looks the same throughout; mixed well Heterogenous = visibly different; least mixed Solution = something has been dissolved. Colloid = usually cloudy.

Calvin….on life.

Nuclear Reactions Fission - splitting of the nucleus; produces much waste (power plant) Fusion - joining of two nuclei; little waste (the sun) Alpha - weakest form of radiation. Beta - 10x stronger than alpha. Gamma - strongest form of radiation.

Chemical Reactions Exothermic releases heat energy resulting in a hot product. Endothermic absorbs heat energy resulting in a cold product. Chemical reactions produce new substances with new properties. Physical reactions allow you to get the original substance back.

Energy Energy can never be destroyed nor created…only changed from one form to another. Energy -the ability to do work. Kinetic energy (motion) depends on mass and velocity. Potential energy (stored or position) Sound is mechanical energy.

Heat Heat - through friction. More movement of atoms equals more heat. No heat is added during a phase change. Absolute zero is the absence of movement; only a theory and exists at 0 K or -273 C Heat is transferred through conduction, convection, or radiation. Conduction - direct contact convection - heat rises and cool falls Radiation - through empty space.

Sound Sound - produced through vibrations Travels in compressions. Fastest in solids. Reflection of sound is an echo. Sound is used in ultrasounds and sonar devices.

Light Can be absorbed, reflected, or transmitted. Changes speed in different mediums. Is an electromagnetic wave. Absorbed by black objects. Reflected by white objects. Allows us to see colors.

Electromagnetic Spectrum Radio waves are weakest. Gamma rays are strongest. Visible light is the only form we see. All travel at the same speed. Frequency increases as form gets stronger. Wavelength decreases as form gets stronger.

Force and Motion Force is a push or a pull Measured in newtons. Causes objects to move, stop or change direction. Speed is distance/time. Velocity is speed and direction. Weight is the pull of gravity on an object. Speed of gravity is 9.8 m/sec/sec

Newton’s Laws of motion 1st law - inertia…something moving wants to keep moving…something still wants to stay still…unless acted upon by a force. 2nd law - mass x acceleration = force. 3rd law - for every action there is an equal and opposite reaction Newton’s law of gravity= if it has mass; it has gravity.

Simple machines Machine - a device used to make work easier. Resistance is the flow against. Work input is always more than work output due to friction. Wedge, pulley, inclined plane, wheel and axle, screw, and lever are the simple machines

Electricity Resistance is lowest when the wire is cold; forms a superconductor. Wire, load, source, and switch are parts to a circuit. Static electricity is the build-up of electricity. Electromagnets are strongest when the wire is wrapped around more times.