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.

pH scale

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

For laughs…

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.

Whew! I need a brain break!

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.

You’re finished…now relax!