Eight Grade Review Part One

1. Eight Grade Review Part One

2. 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

3. 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.

4. 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.

5. 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

6. Periodic Table

7. 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?

8. 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)

9. What type of bonding is this?

10. 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

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

12. Calvin….on life.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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

21. 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.

22. 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

23. 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.