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 0 - 14. • 7 is neutral• 0 - 6 are acids; 0 is strongest• 8 - 14 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 2N2O3?

• 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:

• H2 + O2 -----> H2O

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.