GHSGT Science Review

1. GHSGT Science Review Day 2-PhySci Mrs. M. Davis Mrs. K. Rigdon GHSGT Science Review—2006

2. Atom Numbers • Atomic number = # of protons • Mass number = # of protons and neutrons • Atomic weight/mass = average of all the mass numbers for all known isotopes of an element • Isotope = forms of an element with different numbers of neutrons (Carbon-12, Carbon-14) • In atoms, p = e • In ions, p  e Ions = atoms that have gained/lost electrons • Cations = positive ions (lost electrons) • Anions = negative ions (gained electrons) GHSGT Science Review—2006

3. A little joke…. A hydrogen and an oxygen atom are walking down the street, and the hydrogen is looking very sad. The oxygen asks the hydrogen, “What’s wrong?” The hydrogen says, “I lost my electron.” The oxygen says, “Are you sure?” The hydrogen says, “Yeah, I’m positive!” GHSGT Science Review—2006

4. Periodic Table • Organized by atomic number, not atomic mass • http://www.webelements.com/ Atomic number Atomic mass/weight GHSGT Science Review—2006

5. Solutions • Solutions are composed of a solute and a solvent, mixed together (mixture). • solute = substance in smaller quantity • solvent = substance in larger quantity • solutions in which water is the solvent = aqueous solutions (water is called the universal solvent) • saturated solution = a solution in which the max amount of solute has been dissolved • unsaturated solution = a solution in which an amount of solute less than the max amount has been dissolved • supersaturated solution = a solution in which an amount of solute more than the max amount has been dissolved due to an increase in temp. GHSGT Science Review—2006

6. Kinetic Molecular Theory • KMT = assumes that: • All matter is made of atoms and molecules that act like tiny particles • These tiny particles are always in motion. The higher the temperature, the faster the particles move • At the same temperature, more massive (heavier) particles move slower than less massive (lighter) particles • Three phases of Matter: GHSGT Science Review—2006

7. Phase Changes • Changes of state (solid to liquid, etc.) GHSGT Science Review—2006

8. Energy Transfer • Types of energy = electrical, mechanical, chemical, heat, light, nuclear, etc. • One type can be transformed into another. • Example: photosynthesis changes light E into chemical E • conduction = the transfer of energy as heat between particles as they collide within a substance or between two objects in contact. • convection = the transfer of energy by the movement of fluids with different temperatures. Note: a fluid can be a liquidor a gas. • radiation = the transfer of energy by electromagnetic waves GHSGT Science Review—2006

9. Falling Objects • All objects fall at the same rate (on Earth = 9.8 m/s2) • Remember: rate  speed, rate = change in speed (V) • This picture shows a ball accelerating at approx. 10 m/s2, which is very close to the actual value of 9.8 m/s2 • You will be given the formulas that are needed to solve acceleration and motion problems. GHSGT Science Review—2006

10. Newton’s Laws of Motion • 1st Law = Law of Inertia • Inertia = the ability of an object to resist change in motion. Depends upon mass of the object. • 2nd Law = Relationship of Mass & Acceleration • F = ma Unit of force = Newton (kg•m/s2) • Remember, work = force•distance • No movement = no work! • 3rd Law = Law of Balanced/Unbalanced Forces • Motion is created by unbalanced forces • Friction = a force that opposes motion. 3 types: • Sliding = rubbing hands together • Rolling = walking across a floor (foot rolls) • Fluid = car traveling down the road (through the air) GHSGT Science Review—2006

11. Simple Machines Reduce the effort force even though more work is done. GHSGT Science Review—2006

12. Pulleys • Mechanical advantage of a pulley is determined by counting the number of supporting ropes. • A block and tackle contains many pulleys and has a large mechanical advantage. MA= 1 MA=2 MA= 4 GHSGT Science Review—2006

13. Waves • Longitudinal = energy compress matter as it propagates (ex: sound waves) Because they compress matter, sound waves will move faster through a solid than a liquid/gas. • Transverse = energy radiates as transverse wave; does not need matter to propagate (ex: light, electro-magnetic energy) GHSGT Science Review—2006

14. Waves, con’t. • Electromagnetic spectrum: shows diff. types of transverse waves that carry varying amounts of energy. • Higher frequency = greater energy = short wavelength (X-rays) • Low frequency = less energy = long wavelength (radio, TV waves) GHSGT Science Review—2006

15. Reflection • Reflection = when a wave meets a boundary and bounces off of it. GHSGT Science Review—2006

16. Refraction • Refraction = occurs when a wave crosses a boundary from one medium to another. A wave entering a medium at an angle will change direction. GHSGT Science Review—2006

17. Diffraction • Diffraction = refers to the "bending of waves around an edge" of an object. Diffraction depends on the size of the object relative to the wavelength of the wave GHSGT Science Review—2006

18. Nuclear Chemistry • Fission = splitting of the atom; nuclear power, atomic bomb/nuclear warhead • Fusion = joining of two atomic nuclei; sun • Radioactive decay = unstable nucleus breaks down (nuclei of radioisotopes) - alpha decay: nucleus releases alpha particle which is a helium nucleus - beta decay: nucleus releases a beta particle which comes from the breakdown of a neutron • Half-Life = time it takes for ½ of a radioactive sample to decay • 1 half-life = 50% left • 2 half-lives = 25% left • 3 half-lives = 12.5% left…and so on… uncontrolled fission reaction controlled fission reaction GHSGT Science Review—2006

19. Wave Interactions Constructive Interference

20. Wave Interactions Destructive Interference

21. Electricity & Magnetism • Current = measure of the flow of electric energy; unit is amps • AC: alternating current like outlet • DC: direct current like batteries • electromagnet = a strong magnet created when a iron core (nail) is inserted into the center of a current-carrying a solenoid • the movement of charges causes all magnetism • electric motor = a device that converts electrical energy to mechanical energy • in an electric motor, the current in the coil produces a magnetic field that interacts with the magnetic field of the surrounding magnet, causing the coil to continuously turn GHSGT Science Review—2006

22. Electricity & Magnetism con’t • electromagnetic induction = the production of a current in a conducting circuit by a change in the strength, position, or orientation of an external magnetic field • when the loop of wire moves into or out of the magnetic field, a current is induced in the wire • generator = a device that uses electromagnetic induction to convert mechanical energy to electrical energy. Remember, an electric motor is a device that converts electrical energy to mechanical energy, so they’re opposite GHSGT Science Review—2006

23. Simple Motor A coil of wire turns in a magnetic field. This causes an electric current to flow in the wire.