Evaporation: Cooling by Evaporation - Science Lesson PDF
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This document presents a science lesson on evaporation and its cooling effects. It explains how evaporation works on the skin of humans as well as animals, and how different liquids have different evaporation rates. The document includes questions and answers related to evaporation, temperature, and the average energy of particles in a liquid, and also considers the effect of air coolers.
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Term 2 lesson 1 Evaporation Is the Change of state from liquid to gas Think of water at room temperature (22 °C): Water particles move randomly in different directions Speed of particles is also random and unpredictable Particles: Faster particles have mor...
Term 2 lesson 1 Evaporation Is the Change of state from liquid to gas Think of water at room temperature (22 °C): Water particles move randomly in different directions Speed of particles is also random and unpredictable Particles: Faster particles have more energy Some have enough energy to escape the liquid surface Some particles return to the liquid, while others do not Evaporation and cooling Temperature measures average energy of particles. Water particles have different energy levels. High energy particles escape water, lowering average energy of remaining particles. Evaporation results in cooling. Feeling cooler after swimming due to evaporation on skin. Energy for water to change from liquid to gas comes from skin. Loss of thermal energy from skin causes cooling. Cooling Mechanism Skin produces sweat when too hot. Sweat is the same temperature as skin initially. Evaporation lowers sweat temperature. Thermal energy transfers from skin to cooler sweat. Process continues to lower skin temperature. Alternative Cooling Methods Some animals use water to cool down. Water evaporation provides a cooling effect. Humidity Effects High humidity can prevent sweat evaporation. Some air coolers use evaporation of water to cool air. The air cooler contains a sponge soaked in water. A fan blows warm air from the room through the sponge. Evaporation and cooling of other liquids: Different liquids have different forces holding their particles together. Some liquids have weaker forces than water, while others have stronger forces. Perfumes have weaker forces between particles to evaporate quickly. Perfumes feel colder than water when applied to skin because they evaporate faster, removing more thermal energy. Other liquids, like liquid soap, have stronger forces between particles. Liquid soap evaporates more slowly than water. water feels colder. Water evaporates faster than liquid soap, removing thermal energy faster. Answers
