Name Class Date. Section: Renewable Energy Today Read the passage below and answer the questions that follow.

Transcription

1 Name Class Date Skills Worksheet Active Reading Section: Renewable Energy Today Read the passage below and answer the questions that follow. Solar cells, also called photovoltaic cells, convert the sun s energy into electricity. Solar cells were invented more than 120 years ago, and now they are used to power everything from calculators to space stations. Solar cells have no moving parts, and they run on nonpolluting power from the sun. So why don t solar cells meet all of our energy needs? A solar cell produces a very small electrical current. So meeting the needs of a small city would require covering hundreds of acres with solar panels. Solar cells also require extended periods of sunshine to produce energy. This energy is stored in batteries, which supply electricity when the sun is not shining. Despite these limitations, energy production from solar cells has doubled every four years since Solar cells have become increasingly efficient and less expensive. Solar cells have great potential for use in developing countries, where energy consumption is minimal and electricity networks are limited. Currently, solar cells provide energy for more than 1 million households in the developing world. IDENTIFYING MAIN IDEAS One reading skill is the ability to identify the main idea of a passage. The main idea is the main focus or key idea. Frequently, a main idea is accompanied by supporting information that offers detailed facts about main ideas. In the space provided, write the letter of the term or phrase that best completes each statement or best answers each question. 1. Solar cells convert the sun s energy into a. light. b. heat. c. electricity. d. pollution. 2. What factor regarding solar cells has doubled every four years since 1985? a. the number of solar cells produced b. the amount of energy produced by solar cells c. the number of people who use solar cells d. the price of solar cells 3. Solar cells have great potential for use in Original content Copyright by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor. Holt Environmental Science 7! Renewable Energy

2 Name Class Date a. cities. c. factories. b. private homes. d. developing countries. RECOGNIZING SIMILARITIES AND DIFFERENCES One reading skill is the ability to recognize similarities and differences between two phrases, ideas, or things. This is sometimes known as comparing and contrasting. Read the following questions and write the answers in the space provided. 4. How are solar cells different from most other power sources? 5. How are solar cells of today superior to solar cells of the 1980s? VOCABULARY DEVELOPMENT In the space provided, write the letter of the definition that best matches the term or phrase. 6. photovoltaic cells 7. solar panels 8. energy consumption 9. batteries RECOGNIZING CAUSE AND EFFECT a. power usage b. store energy collected by solar cells c. convert the sun s energy into electricity d. collections of solar cells One reading skill is the ability to recognize cause and effect. Read the following questions and write the answers in the space provided. 10. How are solar cells used today? 11. Why are solar cells particularly suitable for developing countries? 12. Why aren t solar cells used to meet all of our energy needs? Original content Copyright by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor. Holt Environmental Science 8! Renewable Energy

3 TEACHER RESOURCE PAGE!85

4 10.3 The Water Cycle Water is the only substance that exists on Earth in each of its three states. Water easily changes from one state to another. Water sometimes changes its location by changing state in a continuous water cycle: a continuous pattern in nature in which water moves as it changes state above, on, and below the surface of Earth LINKING TO LITERACY Questioning the Text To maintain your reading focus and get more meaning from a text, ask questions as you read. Begin by scanning the page and reading the title and headings. What questions come to mind about the water cycle? Read the fi rst few paragraphs. Stop and refl ect on what you have read. What questions do you have? What more do you want to learn about this topic? Move to the next paragraph and, again, stop to ask questions. The conversation in your head will help you think more deeply about your reading. pattern called the water cycle. The water cycle is self-renewing and constant. The Sun provides the energy to power the water cycle. Changes of State When water changes state in the water cycle, the total number of water particles remains the same. The changes of state include melting, sublimation, evaporation, freezing, condensation, and deposition. All changes of state involve the transfer of energy. Figure 1 shows how the water particles in each state behave as energy is added or removed. solid melting freezing increasing thermal energy of particles sublimation deposition decreasing thermal energy of particles evaporation condensation gas requires energy (heat) releases energy (heat) Figure 1 Energy is gained or lost whenever water changes state. melting: the change of state from a solid to a liquid; occurs when a solid gains thermal energy sublimation: the change of state from a solid to a gas without fi rst becoming a liquid; occurs when a solid gains thermal energy evaporation: the change of state from a liquid to a gas; occurs when a liquid gains thermal energy When solid ice gains thermal energy, it changes state from solid ice to liquid water in a process called melting. Ice cubes in a cold drink, for example, gradually melt. Each spring you see snow melt into slush and puddles. Sometimes adding thermal energy to solid ice causes a change of state from a solid to a gas. This change, directly from a solid to a gas without becoming a liquid, is called sublimation. On crisp, dry winter days you might notice that snow banks shrink, or ice gradually disappears, without first becoming slushy and wet. When water absorbs enough thermal energy, it becomes a gas (water vapour). This process is called evaporation. Water vapour mixes with the air and seems to disappear. For example, wet clothes on a washing line dry because the water evaporates into the air. 270 Chapter 10 Safe Drinking Water NEL

5 When water vapour loses thermal energy and becomes liquid water, condensation has occurred. Rain and dew are examples of condensation. A cold can of pop placed outside on a hot summer day often collects water droplets. This is because water vapour in the air condenses when it is cooled by the cold can. Sometimes, removing thermal energy from water vapour causes it to become a solid, rather than a liquid. Deposition occurs when water vapour changes state directly from a gas to a solid. Deposition is the reverse of sublimation. One example of deposition occurs high in the atmosphere where the temperature is very low. In these conditions, water vapour forms snow without becoming a liquid first. Liquid water can also lose thermal energy and undergo freezing: changing state from a liquid to a solid. We see many examples of this in everyday life. Puddles, ponds, lakes, and even parts of oceans freeze when the water becomes cold enough. Changes of State in the Water Cycle Water moves around Earth in the water cycle. Figure 2 shows where water is found, the state in which it exists, and how it changes from one state to another. Look at Figure 2 carefully to find water in each of its three states. condensation condensation: the change of state from a gas to a liquid; occurs when a gas loses thermal energy deposition: the change of state from a gas to a solid; occurs when a gas loses thermal energy freezing: the change of state from a liquid to a solid; occurs when a liquid loses thermal energy LINKING TO LITERACY Reading Visual Text: The Cycle Map A cycle map is used to illustrate a process that repeats itself. In nature, the water cycle and the life cycle can be illustrated using a cycle map. Can you think of other processes that are repeated in nature? Sun cloud formation (water storage in the atmosphere) deposition sublimation freezing (water storage in ice and snow) precipitation surface runoff (snowmelt into streams) ice water vapour evaporation surface water surface runoff groundwater Figure 2 The water cycle NEL 10.3 The Water Cycle 271

6 runoff: water from precipitation and snowmelt that fl ows over Earth s surface groundwater: water that seeps through soil and cracks in rock; source of water for underground springs and wells aquifer: a geological formation of loose rock or soil that is saturated with groundwater water table: the depth at which loose rock and soil below Earth s surface are saturated with water; the upper boundary of an aquifer Melting, Evaporation, and Sublimation in Nature Solid water includes permanent ice and snow in glaciers and over the polar regions, and ice and snow that form in the winter. Liquid water falls to the ground in the form of rain. Liquid water also forms when winter ice and snow begin to melt. Much of this water is called runoff. Runoff water flows downhill under the influence of gravity, through streams, rivers, and lakes. Some of the water eventually reaches the oceans. All the water on the surface of Earth is called surface water. Some liquid water seeps into the ground. This water, called groundwater, trickles down through openings in the soil and cracks in rocks until it hits bedrock and cannot flow down any farther. The water spreads out until it fills all the available spaces in the loose rock and soil above the bedrock. The loose rock and soil become saturated with water. This saturated area is called an aquifer. The top surface of the aquifer is the water table (Figure 3). Occasionally, natural underground caverns also fill up with water. soil water table groundwater aquifer surface water bedrock Figure 3 Groundwater saturates loose rock and soil to the level of the water table, forming an aquifer. Surface water evaporates and snow and ice sublime from Earth s surface to become water vapour. Water vapour in Earth s atmosphere acts like a blanket that traps thermal energy close to Earth. Melting, evaporation, and sublimation are processes that occur as a result of the increasing thermal energy of water particles (Figure 4). cloud formation (water storage in the atmosphere) Sun ice sublimation water vapour surface runoff (snowmelt into streams) evaporation Figure 4 Ice melts into water or sublimes to form water vapour. Liquid water evaporates when thermal energy is added. 272 Chapter 10 Safe Drinking Water NEL

7 Condensation, Freezing, and Deposition in Nature Once water vapour is in the atmosphere, low temperatures cause the vapour to either condense into a liquid or undergo deposition to form ice crystals. Water droplets and ice crystals in the atmosphere form clouds. Air currents move the clouds around the planet. The water droplets in clouds collide to form larger droplets that fall as rain. Ice crystals fall to the ground as snowflakes. Both rain and snow are forms of precipitation water that falls to Earth s surface. Fallen snow may gradually accumulate as polar ice sheets (areas of ice at the North and South Poles), icecaps (permanent ice that covers land), and glaciers (rivers of ice that slowly flow down mountainsides). At low temperatures, Earth s surface water freezes and forms solid ice. Ice is slightly less dense than liquid water. This explains why, in the winter, lakes and ponds develop a layer of ice that floats on the liquid water underneath. As a result, animals and plants can survive through the winter without being frozen solid. Condensation, deposition, and freezing are processes that occur as a result of a decrease in the thermal energy of water particles (Figure 5). precipitation: solid or liquid water that falls to Earth s surface polar ice sheet: a frozen fi eld of ice covering either the North Pole or the South Pole icecap: a large area of ice that permanently covers land glacier: a river of ice, formed from snow accumulated over hundreds of years, that moves slowly downhill under the force of gravity To watch an animation of the water cycle, Go to Nelson Science cloud formation (water storage in the atmosphere) condensation Sun freezing (water storage in ice and snow) deposition ice water vapour Figure 5 Water vapour condenses and liquid water freezes when thermal energy is removed. Changes with the Seasons Winter snow melts as spring arrives. The snowmelt flows into streams and rivers, and eventually into the oceans. Some of the snowmelt sinks into the ground, becoming groundwater. As surface water evaporates to become water vapour, the water cycle is repeated. Unit Task the Unit Task? How can you apply what you have learned about the water cycle to CHECK YOUR LEARNING 1. Look at Figure 2. Where can you fi nd each of the three states of water? 2. Describe the water cycle. Draw your own labelled diagram. 3. Briefl y describe how solid and liquid water may be converted to water vapour. 4. Describe how water vapour changes into solid and liquid water above Earth s surface. 5. Does all surface runoff move directly into rivers, lakes, and oceans? Explain. NEL 10.3 The Water Cycle 273

8

9 Layers of Atmosphere Reading Questions 1. What are the different layers of the atmosphere based on? 2. What is the layer that most of the weather occurs in? 3. How high above Earth s surface does this layer extend? 4. In which atmospheric layer do we find the o-zone layer? 5. What does the o-zone layer do? 6. What is the stratosphere and the mesosphere called? 7. At what altitude do the gases nitrogen and oxygen become less well mixed? 8. How dense is the thermosphere compared to the air at sea level? 9. Where is the ionosphere? 10. How do radio transmissions use the ionosphere? 11. What happens to temperature as you go higher in the troposphere? 12. Why does temperature increase in the stratosphere? The Atmosphere Layers

10 13. Which layer is the coldest? 14. How hot can the thermosphere get? 15. Draw the layers of the atmosphere in the box! Label each layer and tell how high it goes! The top of the box is 600 km.