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8th Grade Semester Exam

8th Grade Semester Exam. Observation. Observation - recognizing and noting some FACT to gather information about the world You make observations using your five senses . Inference. Inference - a possible explanation or guess about an observation

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8th Grade Semester Exam

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  1. 8th Grade SemesterExam

  2. Observation • Observation - recognizing and noting some FACT to gather information about the world • You make observations using your five senses

  3. Inference • Inference - a possible explanation or guess about an observation • Example: you leave the movie theater and see the ground is wet so you infer that it rained.

  4. Independent Variables and Dependent Variables • The independent variable is WHAT YOU CHANGE ON PURPOSE IN AN EXPERIMENT. • The dependent variable is WHAT YOU MEASURE IN AN EXPERIMENT.

  5. How does the __________(IV) affect the ___________(DV)? IV = cause DV = effect

  6. Two groups of students were tested to compare their speed working math problems. Each group was given the same problems. One group used calculators and the other group computed without calculators. • What is the independent variable? • What is the dependent variable?

  7. Control Group • The control group is exposed to the same conditions as the experimental group, except for the variable being tested. • The control group DOES NOT receive the experimental treatment. • All experiments should have a control group.

  8. Example of Control Group • A researcher is testing the effectiveness of a new antibiotic. Group A receives the new antibiotic. Group B receives a placebo. • Which group is the control group?

  9. #3 • Mass = grams • Volume = mL or cm3 • Length = meters

  10. #4 • Milli = one thousandth • Centi = one hundredth • Kilo = one thousand

  11. #5 • Volume by displacement = final volume – initial volume

  12. # 6 • Volume = length x width x height

  13. #7 • Density = mass/volume

  14. #8 • a variety of sources

  15. #9 • Atoms of the same element have the same number of protons ALWAYS

  16. # 10. You can use the periodic table to determine numbers of subatomic particles. • Number of protons = atomic number • Number of neutrons = atomic mass – atomic number • Number of electrons = number of protons

  17. Reading the periodic table Atomicmass Atomic number 6 12.0 C Element symbol Element name Carbon

  18. #11

  19. Did you know that atoms can gain and lose electrons? • An atom of a given element can gain or lose electrons! • BUT, the number of protons ALWAYS remains the same.

  20. An atom that gains or loses electrons becomes an ION. • An ion is no longer neutral. • Ions are positive or negatively charged.

  21. Anatomthat loses anelectronwillbepositivelycharged.

  22. Anatomthatgainsanelectronwillbenegativelycharged.

  23. #15 • The number of PROTONS in an atom of an element will NEVER change. • Protons ALWAYS stay the same. • You can determine the element by using the number of protons. Ex: An atom with 8 protons will always be Oxygen.

  24. #16. What is a mineral? A mineral is • naturally occurring • Inorganic • solid that • has a crystal structure • a definite chemical composition.

  25. Characteristics of Minerals • Naturally occurring-The mineral must be formed in the earth’s crust. • Inorganic- The mineral cannot come from substances that were once living. • Solid- A mineral has a definite volume and a definite shape. • Crystal structure- The particles of a mineral line up in a pattern that repeats. • Definite Chemical Composition- A mineral contains certain elements in certain proportions.

  26. #16 Continued • Streak – the color of a mineral’s powder • Luster = the way a mineral reflects light • Hardness = uses Mohs scale; determines whether a mineral can be scratched

  27. 18 an 19. The names of the rock types refer to the way the rocks are formed. • Igneous rocks - molten magma that hardens into a rock. • Sedimentary rocks - weathered and broken into pieces then cemented together. • Metamorphic - exposed to intense heat and pressure.

  28. http://www.okaloosa.k12.fl.us/technology/WOWLessons/WOWResources/RockCycleDiagram.gifhttp://www.okaloosa.k12.fl.us/technology/WOWLessons/WOWResources/RockCycleDiagram.gif

  29. 20. Mechanical Weathering The chemical composition does not change – the rock is simply broken down into smaller pieces

  30. 20. Chemical Weathering Rocks and minerals undergo changes in their composition. Atoms are rearranged into new compounds. Agents of chemical weathering include water, oxygen, carbon dioxide, and acids.

  31. 21. • 21. a. mechanical • 21. b. mechanical • 21. c. mechanical • 21. d. chemical • 21. e. chemical

  32. 22. Decomposers • Organisms that break down the remains of other organisms

  33. 22. Humus • Organic material in the soil; remains of dead organisms • Makes soil fertile

  34. 23. What is soil? Weathered rock, minerals, air, water, and humus (decayed organic matter)

  35. 23. • A horizon – topsoil (most fertile) • B horizon – subsoil • C horizon – weathered parent rock

  36. 24. • Humus (decayed organic matter) make soil fertile

  37. 25. How Soil is Formed • sold bedrock is broken into smaller pieces • the pieces continue to undergo weathering and break into smaller pieces 3) organisms such as bacteria, fungi and insects begin to live in the weathered materials 4) the organisms die, decay and add nutrients to the weathered materials to form soil

  38. 26. What is a fossil? A fossil is the remains or evidence of any creature or plant that once lived on the Earth.

  39. 26. Fossils • Fossils give scientists clues to the past. They are able to learn about the past environment and life forms.

  40. 27. Law of Superposition In a sedimentary sequence, the older beds are on the bottom and the younger beds are on the top C B A Which is the youngest? Layer A was deposited first

  41. 28. Relative - compares its age with fossils or rock formations around it. Uses index fossils.

  42. 28. Absolute dating gives us the actual date of the fossil Uses radioactive dating. Half-life – the amount of time it takes for one-half of the parent isotopes to turn into daughter isotopes.

  43. 29. TheGeologic Time Scale • Shows howtheEarth and lifeformsonEarthhavechangedover time.

  44. 30. Cenozoic Era – Mammals are the dominant animals: especially humans.

  45. 31. Conduction • Heat is transferred from one particle of matter to another without the movement of matter itself.

  46. 31. Convection • Heat is transferred by the movement of currents within a fluid (a liquid or gas).

  47. 31. Radiation • Transfer of energy by electromagnetic waves.

  48. 32.

  49. 33. The solid part of the Earth is the lithosphere. It has two parts – the crust and part of the upper mantle. • http://www.deafhoosiers.com/sci/soarhigh/lithosphere/lithosphereComp.html

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