Chapters 2 & 3

1. Chapters 2 & 3 The Scientific Method The Atmosphere The Hydrosphere and Biosphere

2. Section 2-1 Objectives: List and describe the steps of the experimental method Describe why a good hypothesis is not simply a guess Describe the two essential parts of a good experiment

3. 1. What is the experimental method? A series of steps that scientists use to identify and answer questions

4. 2. What are the steps of the experimental method? Observing Hypothesizing and Predicting Experimenting Organizing and Analyzing Data Drawing Conclusions Repeating Experiments Communicating Results

5. 3. What is an observation? A piece of information we gather using our senses. They may take many forms, including descriptions, drawings, photographs, and measurements.

6. 4. What is a hypothesis? A testable idea or explanation that leads to a scientific investigation. It is more than a guess. A good hypothesis should make logical sense and follow from what you already know about the issue.

7. 5. What is a prediction? A logical statement about what will happen if the hypothesis is correct. Predictions are made ahead of time.

8. 6. Why does a hypothesis need to be disproved? Every time a hypothesis is disproved, the number of possible explanations for an observation is reduced. By eliminating possible explanations a scientist can zero in on the best explanation.

9. 7. What is an experiment? A procedure designed to test a hypothesis under controlled conditions. Experiments should be designed to pinpoint cause-and-effect relationships.

10. 8. What are two essential characteristics of a good experiment? A single variable is tested (the independent variable) A control is used (to compare to)

11. 9. What is the independent variable? The factor that changes in an experiment in order to test a hypothesis (the “treatment”). To test for one variable, scientists usually study two groups or situations at one time (a control group and an experimental group), with the independent variable being the only difference between the two groups.

12. 10. What is the experimental group? The group in the experiment that is identical to the control group except for one factor

13. 11. What is the control group? The group that does not receive the experimental treatment.

14. 12. How do you know if your independent variable (the “treatment”) had an effect on what you were testing? You look at the results of your experiment (the dependent variable) and compare the experimental group with the control groups You often use some form of measurement to compare the two groups.

15. 13. What is data? Information gathered during an experiment

16. 14. How can data be organized? • Display the data in tables and graphs • This helps analyze the data and explain it clearly to others • Graphing the data makes the relationships or trends presented in tables easier to see.

17. Bar graphs are useful for comparing the data for several things in one graph.

18. 15. What do scientists base the conclusions on? The results of their experiment. They analyze their data and compare the outcome of their experiments with their prediction.

19. 16. Why is it important for scientists to repeat their experiments? The more often an experiment can be repeated with the same results, the more sure scientists become about the reliability of their conclusions. Scientists look for a large amount of supporting evidence before they accept a hypothesis.

20. 17. How do scientists communicate the results of their studies? They publish articles about their studies in scientific journals.

21. Section 3-2 Objectives Describe the composition of the Earth’s atomosphere. Describe the layers of the Earth’s atmosphere. Explain three mechanisms of heat transfer in Earth’s atmosphere. Explain the greenhouse effect.

22. 1. What is the atmosphere? A mixture of gases that surrounds a planet, such as Earth. Nitrogen, oxygen, carbon dioxide and other gases are all parts of this mixture. Gases can be added to and removed from the atmosphere through living and non-living things. EX: animals remove oxygen when they inhale and add carbon dioxide when they exhale EX: automobiles both add and remove gases

23. The atmosphere also insulates Earth’s surface. This insulation slows the rate at which the Earth’s surface loses heat and keeps Earth’s temperature at a level in which living things can survive.

24. 2. What is the composition of the Earth’s atmosphere? 78% is Nitrogen Nitrogen enters the atmosphere when dead plants and animals decay. 21% is Oxygen Oxygen is mainly produced by plants (especially algae in the ocean). 1% is other gases such as argon, carbon dioxide, methane, and water vapor

25. Gases in the Earth’s Atmosphere:

26. 3. What are the layers of the atmosphere? Troposphere Stratosphere Mesosphere Thermosphere

27. 4. What are some characteristics of the troposphere? Lowest layer of the atmosphere The temp drops at a constant rate as altitude increases This is where weather conditions exist Densest layer of the atmosphere Extends to 18km (11 miles) above Earth’s surface

28. 5. What are some characteristics of the stratosphere? It is above the troposphere Extends from about 18km to 50km (11 to 31 miles) above the Earth’s surface. Temp increases as altitude increases because ozone in the stratosphere absorbs the sun’s ultraviolet (UV) energy and warms the air. Ozone layer occurs here.

29. 6. What is ozone? A gas molecule thatis made up of three oxygen atoms (O3). Because ozone absorbs UV radiation, it reduces the amount of UV radiation that reaches the Earth. UV radiation that does reach the Earth can damage living cells.

30. 7. What are some characteristics of the mesosphere? The layer above the stratosphere. Extends to an altitude of about 80km (50 miles) This is the coldest layer of the atmosphere, where temperatures have been measured as low as -93°C

31. 8. What are some characteristics of the thermosphere? Located farthest from Earth’s surface. Here, nitrogen and oxygen absorb solar radiation resulting in temperatures measuring above 2,000°C. The air in the thermosphere is so thin that air particles rarely collide, so little heat is transferred and it would therefore not feel hot to us.

32. The absorption of x-rays and gamma rays by nitrogen and oxygen causes atoms to become electrically charged. Electrically charged atoms are called ions and the lower thermosphere is called the ionosphere. Ions can radiate energy as light and these lights often glow in spectacular colors in the night skies near the Earth’s North and South Poles (called the Northern Lights).

33. The Northern Lights

34. 9. What are three methods of energy transfer in the atmosphere? • Conduction • Convection • Radiation

35. 10. What is conduction? • The transfer of energy as heat moves through a material when one material touches another (must have direct contact) • EX: You touch a hot iron

36. 11. What is convection? • The movement of matter due to differences in density that are caused by temperature variations and can result in the transfer of energy as heat. • EX: convection currents in a pot of boiling water

37. 12. What is radiation? • Energy that is transferred as electromagnetic waves. • Does not require a medium (solid, liquid or gas) to be transferred • EX: visible light and infrared waves

38. Energy Transfer in the Atmosphere

39. 13. How is our atmosphere heated? • Solar energy reaches Earth as electromagnetic radiation (includes visible light, infrared radiation, and UV light) • About half of the solar energy that enters the atmosphere passes through it and reaches the Earth’s surface. What happens to the rest? • It is absorbed or reflected in the atmosphere by clouds, gases, and dust or it is reflected by Earth’s surface.

40. 14. Why doesn’t the Earth just continue to get warmer and warmer? The oceans and land radiate some of the absorbed energy back into the atmosphere. Dark-colored objects absorb more solar radiation than light-colored objects, so dark colored objects have more energy to release as heat. This is one reason the temperature in cities is higher than the temperature in the surrounding countryside.

41. 15. How do convection currents in the atmosphere move energy? Air warmed by the Earth surface rises and cools off as it rises. Because it cools off, it becomes more dense and then begins to sink. This current moves back toward Earth until it is heated again and becomes less dense. Then it rises again and cools off. This process is called a convection current.

42. Convection

43. 16. What is the Greenhouse Effect? The warming of the surface and lower atmosphere of the Earth that occurs when greenhouse gases absorb and reradiate infrared radiation.

44. The Greenhouse Effect

45. 17. Is the greenhouse effect a good thing or a bad thing? Good!! Without it the Earth would be too cold for life to exist.

46. 18. What are the most abundant greenhouse gases? • Water vapor • Carbon dioxide • Methane • Nitrous oxides • The quantities of carbon dioxide and methane in the atmosphere vary because of natural and industrial processes.

47. Section 3-3 Objectives Name the three major processes in the water cycle. Describe the properties of ocean water. Describe the two types of ocean currents. Explain how the ocean regulates Earth’s temperature. Discuss the factors that confine life to the biosphere. Explain the difference between open and closed systems.

48. 1. What is the hydrosphere? Includes all of the water on or near the Earth’s surface. Includes water in oceans, lakes, rivers, wetlands, polar ice caps, soil moisture, groundwater, and clouds

49. 2. What is the water cycle? The continuous movement of water from the ocean to the atmosphere to the land and back to the ocean.

50. 3. What are three processes that occur in the water cycle? • Evaporation • Condensation • Precipitation