Social Studies Standard Four - Chapter 3 Weather PDF

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Three Weather Introduction In Standard Three, you learnt about weather conditions in your enviro...

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Three Weather Introduction In Standard Three, you learnt about weather conditions in your environment. You learnt about one element of weather, LY temperature, and how to measure it. You also learnt how to protect yourself from hot and cold conditions. In this chapter, you will learn more on the concept of weather, its elements and N changes. You will also learn about rainfall, the effects of heavy O rainfall and how to avoid its effects. The concept of weather SE Weather refers to the day-to-day atmospheric conditions of a given area recorded over a short period of time usually, hours or days. In a given day, the atmosphere can be cloudy, sunny, hot U or cold. It can be rainy or humid. Weather consists of conditions like wind, rain and temperature. It also consists of clouds, humidity, air pressure and sunshine. Weather conditions affect E how we dress and the type of clothes we wear. For example, N we wear light clothes on hot and sunny days. On cold days, we wear jackets and sweaters, or rain coats in rainy conditions. We LI can play outdoor sports and games under sunny conditions. N There are specific areas for recording weather and specific people dealing with weather. A place used to record weather O information is called a weather station. The study of weather is called meteorology. A person studying weather is known as a R meteorologist. Each weather condition is recorded by a specific instrument. FO Elements of weather The elements of weather include temperature, rainfall, sunshine, cloud cover, wind, humidity and air pressure. 29 Social Studies.indd 29 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Temperature This refers to the degree of hotness or coldness of a body, a thing or a place. Temperature is measured using an instrument called thermometer. The measurements of temperature are expressed in Degrees on a Centigrade (°C) or Fahrenheit (°F) scale. A thermometer consists of a scaled tube that contains a liquid called mercury. On the top of the mercury there is a metal LY index. When the temperature is high the mercury inside the tube rises thus pushing the metal index to a certain reading. N When the temperature is low, the mercury goes down, pulling down the metal index to a certain reading. Figure 1 below shows O a thermometer. Note the mercury and the two scales used to measure the temperature. SE U Scale E Glass N LI Metal index N O R Mercury FO Bulb Figure 1: A thermometer 30 Social Studies.indd 30 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Rainfall Rain refers to the water droplets that fall from the clouds to the earth’s surface. Rainfall is the amount of rain that falls in a particular place for a particular period. The instrument for measuring rainfall is called a rain gauge. A measurement of rainfall is expressed in millimetres (mm). A rain gauge has a container with a funnel and collecting bottle. The container is sunk into the ground. When it rains the funnel LY channels the rain water into the collecting bottle. Thereafter, the bottle is removed and the collected water is measured using a N measuring cylinder. Figure 2 shows the structure of a rain gauge. O SE Funnel U Container E N Scaled bottle LI N O Figure 2: A rain gauge Activity 1 R 1. Observe the weather condition at your school and discuss FO it in class. 2. In groups of five pupils, identify and present in class the importance of rainfall in your area. 31 Social Studies.indd 31 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Exercise 1 Answer the following questions: 1. Define the term weather. 2. List seven elements of weather. 3. What do you understand by the term temperature? 4. What instrument is used for measuring temperature? 5. What is the standard unit for measuring temperature? LY 6. What instrument is used for measuring rainfall? 7. What is the unit of measure for rainfall? N 8. Draw a rain gauge and label its parts. O Humidity SE Humidity refers to the amount of water vapour or moisture present in the air. The instrument for measuring humidity is called a hygrometer. This instrument measures the percentage of U moisture present in the air. Figure 3 below shows a hygrometer. E N LI Pointer N O Glass R FO Figure 3: A hygrometer 32 Social Studies.indd 32 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Wind Wind is defined as moving air or air in motion. It is characterised by speed and direction. The instrument for measuring wind speed is called an anemometer. The anemometer has three to four cup shaped bowls which rotate by the power of wind. This rotation shows the speed of wind. The speed of wind is measured in kilometres per hour (km/h). Figure 4 shows an anemometer. LY Cups N Pole O SE U Figure 4: An anemometer Wind direction is measured by an instrument known as wind vane.The instrument has a loose arrow on top which helps to E show the direction of blowing wind. Below the arrow,it has an N indicator of four cardinal directions.Figure 5 shows a wind vane. LI Vane N O Fixed compass point R Pole FO Figure 5: A wind vane 33 Social Studies.indd 33 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Sunshine Sunshine is the light and heat that comes from the sun. It can also be expressed as the direct rays from the sun. The instrument used to measure sunshine is called a sunshine recorder. This tool is made up of clear glass that allows sun rays to pass through. Figure 6 shows a sunshine recorder. LY Glass sphere N O Metal frame SE U E N Figure 6: A sunshine recorder LI Air pressure N Air pressure is the weight of air pressing down on the earth. Sometimes it is known as atmospheric pressure. Air pressure O is measured by an instrument known as a barometer. This instrument consists of a sealed tube and a container of mercury. R Reading occurs when air exerts pressure which pushes the mercury into the sealed tube. The standard unit of measure for FO pressure is millibars (mb). A barometer should be placed in a special building in order to protect it from rain. Figure 7 shows a barometer. 34 Social Studies.indd 34 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Pointer LY Figure 7: A barometer Cloud cover N Cloud cover is the fraction of the sky covered by visible clouds. O Cloudiness is measured by observing and estimating the fraction of the sky covered by clouds, in units called oktas. If you look up SE at the sky and mentally divide it into eight fractions, each fraction is called an eighth or an okta. If the sky is completely clear, that is measured as zero oktas and if the sky is totally covered by clouds U it means all eighths are used to accomodate the clouds 8 oktas. Four oktas would represent a sky that is half covered by clouds. E Exercise 2 N Answer the following questions: LI 1. Describe the weather conditions in your environment. 2. Mention the instruments used for measuring the following N elements of weather. O.(a) Temperature (b) Rainfall (c) Humidity (d) Air pressure 3. Draw the following instruments: (a) a thermometer (b) an R anemometer (c) a rain gauge FO 4. Mention the instrument used for measuring the temperature of a human body. 5. What is the name of a place where weather is recorded? 35 Social Studies.indd 35 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Activity 2 In groups of five pupils: 1. Observe and identify the weather conditions experienced during the morning, afternoon and evening hours for a period of one week. 2. Record the observed weather conditions LY in your exercise book and present them in class. N Change in weather conditions O We have learnt that the condition of the atmosphere in a given place changes frequently. These changes can be observed SE within hours, days or weeks and even months. Sometimes the atmosphere may be cloudy with high humidity and high temperature. After some few hours, it may rain. The rainfall U may stop after a few hours and the atmosphere may be sunny again. Therefore, the elements of weather constantly change. E We can observe fewer elements of weather in a particular day and sometimes much more elements on another day. Changes N in weather conditions affect our daily activities. LI Read the following passage then answer the questions that follow. N Adrean and Fadhili are pupils of Palingo Primary School located O in Kulungu Village. The village receives regular rainfall. Kulungu Village is surrounded by Lake Poma, rivers and a thick forest. R In the evening, Fadhili and Adrean prefer to do exercises in the playground close to their home. FO One day, Fadhili and Adrean went to the ground with their sports gear. Suddenly, Fadhili noticed that there was a sudden weather 36 Social Studies.indd 36 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE change. There was an indication that it was going to rain. It was chilly, and dark as the sky was covered with heavy clouds. Fadhili raised his head to look up and the whole sky was covered with thick clouds. In some parts, the clouds were thick and black. Thunderstorms could be heard from the East. The strength and speed of the wind increased and it was blowing from the direction of the rain. Indeed, this was a sign that it was going to rain. Fadhili said, “My friend, it is going to rain very soon, we LY have to go home!” Both agreed to go back home. When Fadhili arrived at home, N he collected cereal crops that were left to dry under the sun. He O also led the livestock inside the house to protect them from the rain. Adrean collected his clothes and took out a bucket to collect rain water. Thunder, lightning and wind increased. Suddenly, it SE started raining heavily. Changes in weather can have positive impact on the environment. U For example, when it rains, we get enough water. Water is important for plants and animal growth. We use water for domestic E and industrial purposes. In addition, when it rains, it helps to lower the temperature of a place. Rainfall is important for organisms N that live in water and on land. It is the source of water for rivers, LI dams, lakes and oceans. When it rains, the soil gets enough water to support plant growth. N On the other hand, too much rainfall may have several O disadvantages. Heavy rainfall may cause floods which affect residential areas, crops, livestock, roads, railways, power lines R and bridges. In addition, floods may lead to outbreaks of disease such as cholera and typhoid. It may cause death to human beings FO and domestic animals. Too much rainfall also causes soil erosion where the top soil is washed away. 37 Social Studies.indd 37 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Questions 1. What have you learnt from this passage? 2. From the passage, mention four signs of rainfall. 3. What did Adrean do before it started raining? 4. Why do you think the village of Kulungu receives regular rainfall? 5. Mention three benefits of rain that were not mentioned in LY the passage you have read. 6. Explain how you can identify clouds which show that it is N going to rain. O 7. Mention five uses of rain water at your home. Activity 3 SE 1. Go outside the classroom and check if U it is windy, humid or raining. Tell others what you have observed. 2. Tell your fellow pupils about the weather E condition in your region taking into N account: LI a. Rain months b. Dry months N c. Signs of rain O 3. What are the activities carried out during the rainy season in your region? R FO 38 Social Studies.indd 38 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Study the following picture and then answer the questions that follow. LY N O SE Figure 8: The effects of heavy rains Questions U Answer the following questions: 1. What are the effects of heavy rains as seen in Figure 8? E 2. Mention other effects of heavy rainfall in your residential area. N Activity 4 LI Imagine your friend lives in an area with frequent N heavy rains. He or she has invited you to visit him O at his home. 1. Briefly describe the precautions you will take R before you pay him a visit. FO 2. What issues on weather conditions would you ask before you go? 39 Social Studies.indd 39 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Protection against heavy rains It is well known that rainfall is important for both animals and plants. However, sometimes rainfall is accompanied by cold, thunder, and wind. Heavy rain is also accompanied by lightning and thunderstorms. This condition affects human and animal health. We are advised to wear heavy clothes such as jackets, sweaters, and trousers to protect ourselves from cold. In order to avoid the impact of thunder, we are advised to avoid sitting or LY standing under tall trees when it is raining. Tall trees are good conductors of electricity carried by thunderstorms. Playing in N the rain is dangerous for our health. We should also protect ourselves from the rain by staying in safe and secure places. If O the rain is accompanied by thunderstorms, move immediately to the nearest building, avoid standing under trees and electricity poles. SE Sometimes you may be required to continue with your activities U when it is raining. To do so, you must wear a rain jacket. The rain jacket does not allow water to penetrate. In addition, we use umbrellas when it is raining. You are also advised to wear E water proof shoes or gumboots. In areas with heavy rain, it is N advisable not to live in areas likely to be affected by floods. It is advised to build brick houses in elevated areas. It is important LI to watch or listen weather forecast through local news and N social media. This will provide you with more information about weather changes. O Exercise 4 R Answer the following questions: FO 1. Briefly explain the importance of rainfall in your daily life. 2. List any four negative effects of weather changes. 40 Social Studies.indd 40 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE 3. Mention any four advantages of weather changes in our daily activities. 4. Explain how you can protect yourself from the impacts of heavy rains. 5. What is the name of the liquid that is found in a LY thermometer? 6. What is the instrument used for measuring rainfall? N 7. What is the name of a person specialising in studying O weather? Exercise 5 SE Answer the following questions: U 1. What is the meaning of weather? 2. Explain the meaning of weather changes. E 3. What are the effects of heavy rain that you have witnessed or heard about? N 4. Mention five signs of rainfall. LI 5. If you were living in areas with frequent heavy rains, N what precautions would you take? O 6. Write TRUE if the sentence is correct and FALSE if the sentence is incorrect. R (a) Loss of property and death to organisms are the impacts of heavy rainfall ________________ FO (b) The instrument used to measure rainfall is called a barometer ____________________ 41 Social Studies.indd 41 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE (c) The four elements of weather are sun, rain, wind and clouds ____________________ (d) When working in the rain you should wear a rain jacket __________________ (e) One of the means of reducing the impacts of rainfall is cutting down all trees _________________ LY (f) We wear heavy clothes when it is sunny _________ N 7. Match the items in list A against those in list B by writing the letter of the correct sentence beside the O item number. LIST A LIST B (i) Signs of rainfall SE (a) barometer _____________ (b) dark clouds, thunder U (ii) Clouds which bring and lightning. rainfall __________ E (iii) Advantages of (c) frequent rainfall rainfall to plants N and human beings (d) rainfall __________ LI (e) get water for growth of (iv) Farming throughout N the year _________ crops and domestic use O (v) Atmospheric (f) thunderstorms and red pressure _________ clouds R (vi) The main source of water to rivers, FO (g) anemometer lakes and oceans ____________ (h) dark or grey clouds 42 Social Studies.indd 42 30/07/2021 13:51  FOR ONLINE USE ONLY DO NOT DUPLICATE Vocabulary Atmosphere the air or gases surrounding the Earth Forecast to predict or estimate future events Infrastructure physical structures such as roads, buildings and power Okta Is a unit used to express the estimated LY degree of cloudness in a sky of a particular place at a particular point of time N Reflect throw back light, heat or sound O Thunder a loud crashing noise heard after a lightning SE U E N LI N O R FO 43 Social Studies.indd 43 30/07/2021 13:51