Grade 6 | Science | Unit 3 - Concept 1 - Lesson 2 - Energy and water скачать в хорошем качестве

Grade 6 | Science | Unit 3 - Concept 1 - Lesson 2 - Energy and water

Welcome dear students! Water cycle :It is the continuous movement of water among different water reservoirs. Water reservoirs :They are storage locations of water on Earth. Water reservoirs include : • Oceans. • Seas. • Lakes. • Rivers. • Glaciers. • Soil. • Rocks. • Living organisms. • Atmosphere. • The main processes and steps that move water among these reservoirs are evaporation, condensation, precipitation, runoff and collection. • All these processes and steps depend on energy and force. The factors that affect the movement of water in the water cycle : Solar energy : • The Sun is the most important source of energy that affects the water cycle. • The sunlight (solar radiation) that comes from the Sun includes thermal energy that causes the change of the state of water through the water cycle, where : • During melting, when water changes from solid state (ice) to liquid state (liquid water), it gains energy. • During evaporation, when water changes from liquid state (liquid water) to gas state (water vapor), it gains energy. • During condensation, when water changes from gas state (water vapor) to liquid state (liquid water), it loses energy. • During freezing, when water changes from liquid state (liquid water) to solid state (ice), it loses energy. Gravity Force • Water starts to move or change its way of movement when a force affects it. • There is a main force that affects the water cycle, which is gravity force. Effects of Gravity on Water Water can be pulled downward by gravity force, where it causes: 1. Falling of melting ice crystals and water droplets found in clouds back to Earth's surface leads to the flowing of liquid water downhill into streams and rivers towards larger water bodies. 2. Flowing of water in solid state (ice) in glaciers from higher elevation areas to lower elevations areas leads to the frozen water melts and flows into the ground or the water bodies. 3. Flowing of liquid water from higher elevation areas to lower elevation areas leads to leakage of liquid water down into the ground then to groundwater reservoirs. Energy and the water cycle : • From the previous activities, you have known that when water changes from one state to another, it gains (absorbs) or loses (releases) energy. • Gaining or losing energy affects the water particles (molecules) in the air. • The movement of air from one place to another in the presence of difference in temperature leads to : • Changing of liquid water to water vapor and this process is known as "evaporation". • Changing of water vapor to liquid water (in the form of water droplets) and this process is known as "condensation". Transfer of energy : • Condensation and freezing are two processes occur when water particles lose thermal energy. • Melting, evaporation and transpiration (in plant leaves) are processes occur when water particles gain thermal energy. Evaporation : • Through the water cycle, the Sun heats water in oceans, seas, lakes, rivers, streams and other water bodies. • This leads to evaporation of water and changing it into water vapor due to gaining thermal energy. Transpiration :It is a type of evaporation that takes place through the stomata on the plant's leaves. About 10% of water vapor in the air comes from transpiration of plants. Example shows transpiration: 1. Bring two plants differ in size. 2. Put one of them in the direct sunlight and the other in a shaded area. 3. Tie around a leaf from each plant a plastic bag. 4. You can notice that water droplets are formed inside each of the two bags. When the amount of the energy comes from the Sun increases, the transpiration in plant's leaves increases. Condensation: Condensation occurs when: • The air that is saturated with water vapor cools due to decreasing of air temperature, so the water vapor changes into liquid water. • Clouds are formed, where they consist of tiny water droplets that are condensed in the air, so water vapor releases its energy and changes into liquid water. How clouds are formed? • Clouds are formed due to condensation of water vapor into water droplets that attach to particles of dust, smoke, .... etc. in the air. • When very large numbers of these water droplets join together, they form clouds. Note Clouds are made up of millions of tiny water droplets, when these water droplets become too heavy, they fall in the form of rain. #Science_Grade6 #mrraoufashraf #Science_Grade6 #WaterCycle #CloudFormation #Condensation #Weather #ScienceFun #LearnScience Mr. Raouf Ashraf