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Living By Chemistry

Living By Chemistry. Unit 3: WEATHER Phase Changes and Behavior of Gases. In this unit you will learn:. about proportional relationships about temperature scales and how thermometers work the effects of changing temperature, pressure, and volume on matter about the behavior of gases

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Living By Chemistry

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  1. Living By Chemistry Unit 3: WEATHER Phase Changes and Behavior of Gases

  2. In this unit you will learn: • about proportional relationships • about temperature scales and how thermometers work • the effects of changing temperature, pressure, and volume on matter • about the behavior of gases • how to read weather maps and make weather predictions

  3. Lesson 1: Weather or Not • Weather Science

  4. Day 1 ChemCatalyst • The table gives the current weather conditions in Miami, Florida (shown on the weather map in the following slide with a star). Predict the weather for later today. Indicate whether you think the current conditions will increase, decrease, or stay the same. Explain your reasoning. • Current Conditions at 1:30 P.M. in Miami, Florida

  5. ChemCatalyst (cont.) • Weather map for October 27, 2008:

  6. Key Question • What causes the weather?

  7. You will be able to: • explain the phenomenon of weather in general terms • list the variables meteorologists study or measure in order to predict the weather • describe the basic components of a weather map

  8. Prepare for the Activity • Work in groups of four. • Weather: The state of the atmosphere in a region over a short period of time. Weather is the result of the interaction among Earth, the atmosphere, water, and the Sun. It refers to clouds, winds, temperature, and rainfall or snowfall.

  9. Discussion Notes • Several factors affect the weather in North America. • • jet stream • • temperature • • cloud cover • • fronts • • precipitation • • pressure

  10. Discussion Notes (cont.) • Jet stream

  11. Discussion Notes (cont.) • Temperature highs in degrees Fahrenheit

  12. Discussion Notes (cont.) • Cloud cover

  13. Discussion Notes (cont.) • Fronts

  14. Discussion Notes (cont.) • Precipitation: rain and snow

  15. Discussion Notes (cont.) • Air pressure highs and lows

  16. Discussion Notes (cont.) • There are connections between the different maps. • The precipitation map is most closely associated with low-pressure areas and with weather fronts of all kinds. • The curves of the jet stream map generally match the curves of the temperature maps. • The lows on the air pressure map are associated with the warm and cold fronts. • Rain requires clouds overhead. However, the presence of clouds does not necessarily mean precipitation.

  17. Discussion Notes (cont.) • In the jet stream, air moves swiftly from west to east across the United States.

  18. Wrap Up • What causes the weather? • Weather consists of precipitation, clouds, winds, and temperature changes. • Weather is the result of interaction among Earth, the atmosphere, water, and the Sun. • The jet stream, temperature, cloud cover, weather fronts, precipitation, and air pressure are variables that are all tracked by meteorologists in order to forecast the weather.

  19. Check-in • What do weather maps keep track of? How do they help meteorologists?

  20. Lesson 2: Raindrops Keep Falling • Measuring Liquids

  21. Lesson 3: Having a Meltdown • Density of Liquids and Solids

  22. Day 2 ChemCatalyst • Water resource engineers measure the depth of the snowpack in the mountains during the winter months to predict the amount of water that will fill the lakes and reservoirs the following spring. • Do you think 3 inches of snow is the same as 3 inches of rain? Explain your reasoning. • How could you figure out the volume of water that will be produced by a particular depth of snow?

  23. Rain Gauge • Which of these containers would make the best rain gauge? Explain your reasoning.

  24. Does the same amount of rain fall on each area? How could you measure the amount of rain that falls on the objects?

  25. Key Question • How much water is present in equal volumes of snow and rain?

  26. You will be able to: • make density calculations, converting volumes of liquids and solids • explain how phase changes affect the density of a substance • use density equations to calculate the volume of water in a sample of snow or ice

  27. Discussion Notes (cont.) • You can determine the density of water by measuring the mass of a certain volume of water. The density, D, is the mass, m, divided by the volume, V: • D = • The densities of snow and ice are less than the density of water. m V

  28. Discussion Notes (cont.) • The graph you created allows you to compare the densities of the different phases of water. • The relationship D = can also be written as m = DV. m V

  29. Discussion Notes (cont.) • For any proportional relationship, the graph is a straight line that passes through the origin, (0, 0). • Scientists measure snowpack in terms of depth—meters or feet—and then make conversions to obtain the volume of water.

  30. Wrap Up • How much water is present in equal volumes of snow and rain? • In density calculations, mass and volume are proportional to each other. • The formula D = can also be written m = DV. • When a substance changes phase (from solid to liquid to gas), its density changes. The mass stays the same, and the volume changes. • Water is denser than snow. Ice is less dense than water. m V

  31. Check-in • Imagine that you have equal masses of snow and rain. Which has a greater volume? Explain your thinking. • What is the mass of 14 mL of rainwater?

  32. Lesson 4: Hot Enough • Thermometers

  33. Day 3 ChemCatalyst • The weather forecast in Moscow, Russia, calls for a 60% chance of precipitation with highs reaching 30 °C, while in Washington, D.C., the weather forecast calls for a 70% chance of precipitation with highs reaching 50 °F. • Which city will be warmer? Explain your thinking. • Do you think it will rain or snow in either of the two cities? Explain your reasoning.

  34. Key Question • How is temperature measured?

  35. You will be able to: • create a thermometer and a temperature scale • describe how a thermometer works • explain the Fahrenheit and Celsius temperature scales

  36. Prepare for the Lab • Work in groups of four.

  37. Discussion Notes • The volume of matter changes in response to changes in temperature.

  38. Discussion Notes (cont.) • Many thermometers contain a liquid, such as alcohol or mercury.

  39. Discussion Notes (cont.) Gases expand and contract as the temperature changes.

  40. Discussion Notes (cont.) • To set a temperature scale, you need at least two measurements. • Melting point or melting temperature: The temperature at which a substance melts or freezes. At this temperature, both solid and liquid phases of the substance are present. • Boiling point or boiling temperature: The temperature at which a substance boils or condenses. At this temperature, both liquid and gas phases of the substance are present.

  41. Discussion Notes (cont.) • Once you have set a scale with two points, you can determine other temperatures. • In 1724, German physicist Daniel G. Fahrenheit invented the first modern thermometer—the mercury thermometer. • Degree: The increment of temperature that corresponds to one unit on a thermometer. The size of a degree depends on the temperature scale used.

  42. Discussion Notes (cont.) • In 1747, Anders Celsius, a Swedish astronomer, created a thermometer with a different scale. • Degrees Celsius and degrees Fahrenheit both measure the same thing (temperature). 9 5 °F = (°C)+32 or °F = 1.8(°C)+32

  43. Wrap Up • How is temperature measured? • The volume of matter changes in response to changes in temperature. • Almost all substances expand on heating and contract on cooling. • The change in volume of a liquid can be used to measure temperature changes. • The relationship between the Fahrenheit scale and the Celsius scale is described by the formula °F = (°C) + 32. 9 5

  44. Day 4 ChemCatalyst • The temperature is 37 °C in Spain in July. How does this compare with body temperature, which is 98.6 °F?

  45. Lesson 5: Absolute Zero • Kelvin Scale

  46. Day 5 ChemCatalyst • Researchers have recorded the temperature on Triton, a moon of Neptune, as –235 °C. • Do you think carbon dioxide, CO2, would be a solid, a liquid, or a gas at this temperature? Explain your reasoning. • What do you think is the coldest temperature something can get to? What limits how cold something can get?

  47. Key Question • How cold can substances become?

  48. You will be able to: • describe the relationship between the Celsius and Kelvin temperature scales • explain the concept of absolute zero • describe the motion of gas molecules according to the kinetic theory of gases

  49. Prepare for the Computer Activity • Work individually.

  50. Discussion Notes • On the Celsius scale, the temperature at which the volume of a gas is theoretically equal to 0 is °273 ｰC. • K = °C + 273 • °C = K – 273

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