Physical Science Review for the GCRCT

1. Physical Science Reviewfor the GCRCT 8th Grade Physical Science

2. The Scientific Method • Step 1: Ask a Question • Step 2: Form a hypothesis(based on observations) • Step 3: Test the hypothesis (experiment) • Step 4: Analyze the results (data from exp.) • Step 5: Draw conclusions • Step 6: Communicate results

3. The Scientific Method • Theory – An explanation based on observations, hypothesis and experiments. Ex: Big Bang. • Law – Summary of many observations and experimental results telling how things work. Ex: All of Newton’s Laws • Models – a representation of an object or system.

4. The Basics of Physical Science • All sciences are based in physical science: • Geology – studies Earth and Earth activities • Biology – studies how living things work • Botany – studies plant life • Ecology – studies environmental issues

5. International System of Units (SI) • Based on the number 10 • Prefixes: milli (1/1000th), centi (1/100th), deci (1/10th), main unit, kilo (1000) • Length = meters • Mass (not weight) = grams • Volume = liters (liquids) cm3 (solids) • Weight depends onmassandgravity measured in Newtons

6. Measurements • Area = Amount of surface: length x width (e.x. cm2) • Volume = How much an object can hold: length x width x height (e.x. cm3) • Density = Amount of matter in a given space: mass volume ex: g/ml Force = a push or pull, measured in Newtons (as isweight)

7. Measurement Tools • Thermometer - measures temperature • Balances – measures mass (in grams) • Ruler – measures length (in meters) • Graduated cylinder – measures volume

8. Physical Properties/Changes • Physical properties include changing states (solid/liquid/gas/plasma), measurements such as length, height, density- keeps same identity. Changing any of these causes a physical change. • Chemical properties change the identity a substance through burning (applying heat) or creating a chemical reaction (ex: rusting). When this occurs, you have a chemical change that makes a new substance.

9. Atoms • Atom – smallest part of an element. • Atoms are made of protons (+),neutrons and electrons (-), which are outside the nucleus. • Electrons are in an electron cloud. They can move from level to level, or they can bond with other atoms. • Isotopes – are atoms that have the same # of protons, but different # of neutrons (ex: C 14)

10. Atoms and Electron Bonding • Ions – Charged atoms when valence electrons transfer from one atom to another (ionic bonding). • Covalent bonding – Electrons don’t transfer, but the atoms combine by sharing valence electrons.

11. The Periodic Table • Atomic number - # of protons – how the Periodic Table is arranged. • Mass number - # of protons and neutrons • amu – atomic mass units (measurement) • Elements – cannot be broken down into simpler substances.

12. The Periodic Table • Arranged by family/group (same physical and chemical properties), and rows/periods (has same repeating patterns). Classified by metals, metalloids and non-metals. • Largest group is metals. Good conductors of electricity/heat, malleable, ductile, can react with water.

13. Mixtures and Compounds • A mixture is when 2 or more substances are mixed, but there is no chemical bonding (they can be separated). Ex: cake mix. • A compound is a substance made up of 2 different elements that are chemically bonded. Ex: NaCl, H20 The subscript number is the number of atoms in a compound. H20 means there are 2 atoms of hydrogen.

14. Solutions • Solutions are when one substance is dissolved into another substance (salt water) • The solubility of most solids increases as temperature increases (ex: higher temps. melt butter). • Water is the universal solvent.

15. Gravity, Mass and Weight • Gravity: A force of attraction between 2 objects, depending on their mass and distance from each other. • Weight is dependent upon gravity. • Mass does not change when gravity changes, only weight.

16. Friction • Friction is a force that opposes an object’s motion. • Sliding – moving items across a surface • Rolling – use of wheels • Fluid – any gas or liquid (water, air, etc.) Air resistance is an example. • Static – built up electric charges • Viscosity – A liquid’s resistance to flow. The more dense, the greater the viscosity.

17. Force • Can cause an object to speed up, slow down, or change direction, is a push/pull, and is measured in newtons. • You have to exert a greater force to overcome gravity (inertia) or friction. • Net force is the total extra force needed to move an object. (10N west vs. 5 N east = 5 N west) • Gravity depends on mass and distance. • Greater mass = greater gravity • Greater distance = less gravity

18. Speed, Velocity & Acceleration • Frame of reference is what you are using to compare the movement of an object. • Speed is distance over time (ex. km/hr) • Constant speed graphs – show no change. • Velocity is speed plus direction (ex. km/hr south) Acceleration – change in speed or direction

19. States of Matter • Freezing/boiling points are physical properties. • Solids – particles can’t overcome gravity to move • Liquids – particles can move, but not break away from each other • Gas – particles can move past each other, creating areas of empty space. Particles move faster when temperature increases.

20. Pressure and Temperature • Pressureis the amount of force over a given area. • Boyle’s Law: when volume changes, pressure changes (ex: blowing up a balloon) • Charles’s Law: When temperature changes, volume and pressure changes.

21. Fluid Pressure • Like gravity, atmospheric pressure decreases as you move upwards (less on a mountain) • Fluids (gases/liquids) travel to areas of leastpressure (ex: straws, your ears on airplane). • Fluids flow equally in all directions.

22. Fluids and Density • When fluids have different densities, they separate (less dense on top). • Denser objects can float if they have a change in shape (ex: ship)

23. Energy Transfers • Conduction – transfer of energy (electrical or thermal) by direct contact. (Ex: boiling water on stove – heating unit to pot to water) • Convection – Transfer of heat by the movement of the liquid or gas (boiling water) • Radiation – Transfer of heat through matter or space (ex: the Sun or other electromagnetic waves.)

24. Energy Conversions • Energy is never lost or created, it just changes form (Laws of Conservation) • All energy transfers into some form of thermal (heat) energy (ex: light bulb) • Mechanical energy is energy of motion or position (ex: machines)

25. Energy • Potential Energy– stored energy • Kinetic Energy – Energy in motion • Energy Resources: • Fossil Fuels and Nuclear Energy are nonrenewable. • Fossil Fuels are our greatest source of energy.

26. Momentum • Newton’s 2nd Law: Greater the mass and velocity, the greater the momentum (ex: large truck vs small car) • Law of Conservation of Momentum: Momentum is not lost or gained (same after an accident as before the accident).

27. Waves • Amplitude – the height of a wave from area of rest to top of crest. Shows the amount of energy of wave. • Wavelength – distance from crest to crest or trough to trough. The number of wavelengths passing a point during a given time is frequency.

28. Wave Types Transverse Waves • Do not need a medium. • Examples are all electromagnetic waves. Longitudinal Waves Sometimes called mechanical waves • Resemble a “slinky” – series of compressions and rarefactions • Sound waves are longitudinal waves

29. Sound • Travels approx. 350 m/s. • Can travel faster through solids. • Amplitude = energy (how loud) • Frequency = how fast wave is traveling • When you or sound approach, sound increases. As you move away, it decreases. This is the Doppler effect (change in frequency).

30. Light • Light travels in a transverse wave (300 million m/sec in a vacuum) • Divided by wavelengths: Radio to Gamma Color wavelengths: long = red, short = violet • All wavelengths together make white, lack of all light reflected is black. • The wavelengths reflected back are the colors you see.