Welcome dear students! Today we are going to learn about A Journey through States of Water from Class 6 Science. Let us begin with a beautiful thought from the Thirukkural which says, if it does not rain well, even the mighty ocean will be drained. This reminds us how precious water is. On a bright summer afternoon, Aavi and Thirav enjoy their shikanji, which is lemonade. Looking at the ice, Thirav wonders if ice and water are different substances because ice feels hard and can be held, while water cannot. Aavi disagrees and says they are the same substance. She suggests putting water in a refrigerator freezer to see if it converts to ice. Thirav agrees but wonders if something gets added to the ice in the freezer. Do you think Thirav is right? How can you find out? Let us explore this together.
[CHECKPOINT]
Activity eight point one asks us to let us observe. Put an ice cube in a cup, leave it on the table, and observe. You will see the ice gets converted into water. What can you conclude? Does this mean ice and water are the same substance? Yes, ice and water are two forms of the same substance. These forms are also called states. These different states of water show many differences in their behaviour. Water flows but ice does not. Water splashes but ice does not. Now let us move to section eight point one, investigating water's disappearing act. On a rainy morning, Aavi and Thirav observe many water puddles in the playground. By evening, some water has disappeared. Aavi thinks it was absorbed by the soil. What do you think? Have you noticed puddles disappearing? Where does the water go? After washing utensils, water on them dries up. Does it seep through the utensils? Thirav says no. Let us investigate.
[CHECKPOINT]
Activity eight point two asks us to let us investigate. Take a tablespoon of water on a steel plate. Observe whether the water seeps through to the other side. Keep observing at regular intervals until the water completely disappears. What do you infer? Is this activity enough to conclude that water does not seep through a steel plate? If it does not seep through, where has the water gone? This water gets converted into a gaseous state called water vapour. Water vapour is another state of water. Think of another example: sprinkling water on a hot pan for dosa. It disappears and becomes steam, which is water vapour with some tiny water droplets. The process of conversion of water into its vapour state is called evaporation. Evaporation takes place continuously, even at room temperature. Other examples include drying of wet clothes, a mopped floor, and sweat on our body. So, puddle water disappears due to both seeping into the ground and evaporation. Hand sanitiser also disappears when rubbed on hands.
[CHECKPOINT]
Now, let us draw. I want you to draw a detailed sketch, with labels and a caption, showing exactly what happens to the water when it is sprinkled on a hot pan. Here is a do you know note: water vapour is actually invisible, but the presence of tiny droplets of water in the steam makes it visible. Now let us move to section eight point two, another mystery. The next day, Aavi, Thirav and friends make lemonade with cold water and ice cubes. After a few minutes, they notice droplets on the outer surface of the glass tumbler. Activity eight point three: Let us experiment. Take cold water in a glass tumbler. Add a few ice cubes. Leave it undisturbed for five minutes and observe. Record your observations and questions in Table eight point one. You can also touch the outer surface to feel for changes. You will observe tiny water droplets appearing on the outer surface. Initially they deposit and combine to form bigger drops. Where do they come from? Could ice have melted and come out? Could water have seeped out?
[CHECKPOINT]
Aavi and Thirav argued with a chain of reasons. Let us look at Figure eight point four. One reason suggests that some water may have seeped out of the glass tumbler. Another counters this by saying it cannot seep out because the water level inside has not decreased. A third reason adds that the level might have decreased, but not enough to be seen, and suggests that with a tall and narrow bottle, even a slight change would be noticeable. Finally, they propose taking water at room temperature in another tumbler to test if any water seeps out. Please continue the discussion on these given reasons, or conduct activities to find evidence for them to help in your discussion. Where else have you seen such droplets? Dew drops on plants, especially in the morning. When boiling water in a covered utensil, drops form on the inner side of the lid. When the water vapour present in the air comes in contact with a cold surface, it forms water droplets. The process of conversion of water vapour into its liquid state is called condensation.
[CHECKPOINT]
So, the droplets on the glass tumbler are due to condensation of air's water vapour. Let us investigate with Activity eight point four: Let us measure. Take a glass tumbler half filled with water containing a few ice cubes. Cover it with a small steel plate. Weigh it on a digital weighing balance. Observe the reading on the balance and record the weight after every five minutes. Continue observing for thirty minutes. Record your observations in Table eight point two. The table has two columns: time and mass of water. The time rows are zero, five, ten, fifteen, twenty, twenty five, and thirty minutes. Predict what will happen to the mass. Will it increase, decrease, or remain the same? Do your findings match your predictions? You will observe water droplets on the glass tumbler. Water vapour from the air comes in contact with the cold surface and gets converted into water droplets through condensation. There is an increase in the reading on the digital weighing balance. Can we conclude water is not seeping? Can we conclude the water is only due to condensation? Not conclusively from this activity alone. What more can you do? How would you modify the activity?
[CHECKPOINT]
Repeat it with a modification. Mark the water level on the glass tumbler with a permanent marker or visible tape. You will observe the water level does not go down, but extra water collects on the outer surface. This shows water is not seeping from the glass tumbler and the extra water is getting collected because of condensation. Here is a more to do note. The amount of water vapour in the air is also known as humidity. The daily humidity data for your area is reported in newspapers and other sources. Compile the data for the year and study any patterns, if present. Now, section eight point three asks, what are the different states of water? Water exists in three different states in daily life. In the solid state, it exists as ice. On heating, ice melts into liquid. On further heating, water converts to gaseous state. Let us perform Activity eight point five to identify properties. Put an ice cube in one container and transfer it to another of different shape. Notice the shape does not change. Record in Table eight point three.
[CHECKPOINT]
Pour water between different containers. It flows and takes the container's shape. Pour water on a clean surface; it spreads. Water vapour spreads out to fill all available space. Table eight point three compares these. Ice retains its shape, does not flow or spread. Water flows, changes shape, takes container shape, keeps constant volume, and spreads. Water vapour spreads everywhere, has no fixed shape, and exists invisibly at room temperature. Other substances like wax, oil, and ghee also show these states. Solids include stones, wood, and glass. Liquids include milk and oil. Gases include oxygen and carbon dioxide. Smell of cooking food reaches us because gas particles spread through air. Section eight point four asks, how can we change the states of water? To change ice to water, or water to vapour, supply heat. To change water to ice, place it in a cold environment like a freezer. Water freezes into ice. Taking it out melts it back. Wax in a candle melts when heated and solidifies when cooled. Coconut oil solidifies in winter. Substances change states on heating or cooling. The process of conversion of a solid into liquid state is called melting. The process of conversion of liquid into solid state is called freezing.
[CHECKPOINT]
Activity eight point six asks us to complete the diagram. Fill up the blank boxes in Figure eight point five, marked as A, B, C and one, two, three, four, for the conversion of different states of water. Use the words given in the box: Liquid, Freezes, Evaporates, Gas, Condenses. Two words are already filled for you. Box A is Solid. Box B is Liquid. Box C is Gas. Process one is Melts. Process two is Freezes. Process three is Evaporates. Process four is Condenses. This shows the complete cycle of state changes. Now section eight point five explores how water can be evaporated faster or slower. Conditions like temperature, wind, and surface area affect evaporation speed. Activity eight point seven asks us to investigate. Take water in a small bottle cap. Take the same amount of water on a plate. The exposed areas differ. Keep them near each other. Record the time for complete evaporation in Table eight point four. The bottle cap with less area takes longer. The plate with more area takes less time. Conclusion: spreading water increases exposed area, so evaporation is faster. What if milk is used? It would behave similarly. Design another activity changing one condition, like air movement, and record data in Table eight point five.
[CHECKPOINT]
Activity eight point eight explores further. Take two identical bottle caps with equal water. Place one in sunlight, one in shade. Observe every fifteen minutes. Record evaporation time. Water evaporates faster in sunlight. Clothes dry faster on hot, sunny days. They also dry faster on windy days because increased air movement speeds up evaporation. Here is a do you know note. The amount of water vapour in the air is more on rainy days, making them more humid. High humidity slows evaporation, so clothes dry slowly. To dry them faster, increase air movement. Section eight point six discusses the cooling effect. Aavi notices water in an earthen matka is colder than in a steel pot. Why? Water seeps through the pot's pores and evaporates, taking heat from the water inside, causing cooling. Sprinkling water on floors or roofs cools them. A fan cools us by helping sweat evaporate. Rubbing sanitiser feels cool due to evaporation. Activity eight point nine asks us to make a model. Build a pot in pot cooler. Take two earthen pots of different sizes. Fill the larger pot's bottom with sand. Place the smaller pot inside. Fill the gap with more sand. Pour water into the sand. Cover the top with a lid or wet jute sack. Wait four to five hours. The evaporation from the wet sand cools the inner pot. Keep fruits and vegetables inside to maintain freshness. Add water regularly to keep sand moist. A surahi is a traditional clay pot that uses this principle.
[CHECKPOINT]
Section eight point seven asks, how do clouds give us rain? Condensation returns evaporated water to Earth. As air rises, it cools. At certain heights, water vapour turns into droplets around dust particles. These float and form clouds. Droplets combine, become heavy, and fall as rain. Water vapour rises because it is lighter than air. Sometimes it falls as hail or snow. Aavi writes a poem about water's journey. You can complete it with your own lines. Activity eight point ten demonstrates the role of dust in cloud formation. Caution: handle burning paper carefully. Take an empty one litre plastic bottle. Pour one cup of water inside. Close the lid tightly. Squeeze and release the bottle continuously for two to three minutes. Observe the space above the water. Repeat after adding a small burnt piece of newspaper. You will see haziness, or clouds. The burnt paper provides dust particles for water vapour to condense around. Activity eight point eleven represents our understanding of water state changes and movement. Label Figure eight point nine with Cloud, Lake, Ocean, River, Groundwater, Evaporation, Condensation, Rain, and Snow. Water evaporates from oceans and land, condenses into clouds, falls as precipitation, and flows back to oceans. This circulation of water is known as the water cycle.
[CHECKPOINT]
Only a small portion of Earth's water is usable. Most is in oceans. Rising population increases demand, causing shortages. We must use water wisely, avoid waste, and keep water bodies pollution free. You will learn more in Nature's Treasures. Keywords to remember include condensation, evaporation, freezing, gas, humidity, liquid, melting, solid, water cycle, water vapour, experiment, investigate, observe, predict, question, reason, and record. Summary key points: The process of conversion of water into its vapour state is called evaporation. The process of conversion of water vapour into its liquid state is called condensation. Water is found in different states solid, liquid and gas. Water changes its state on heating or cooling. Conditions which make evaporation faster or slower are exposed area, humidity, and air movement. Evaporation causes cooling effect. The water vapour in the air condenses to form tiny droplets of water, which appear as clouds. Many tiny water droplets come together and fall down as rain, hail or snow. The circulation of water between the Earth surface and atmosphere is known as the water cycle. We used observation, questioning, possible reason and experimenting to find out these concepts.
[CHECKPOINT]
Now let us enhance our learning by answering the exercise questions. Question one asks which best describes condensation. The correct answer is the conversion of water vapour into its liquid state. Question two asks where evaporation is very important. For colouring, it is important in water colours. For writing, it is important in ink pens. Question three asks why natural grass feels cooler than plastic grass. Natural grass holds water that evaporates, creating cooling. Plastic grass does not. Question four asks for other evaporating liquids. Examples include alcohol, petrol, nail polish remover, and hand sanitiser. Question five asks why fans dry clothes despite cooling. Evaporation needs heat energy from surroundings. A fan moves air, carrying away vapour and allowing faster evaporation, which feels cool. Question six asks why sludge is left in heaps for three to four days. It allows water to evaporate, reducing weight and volume, lowering transport costs, and making it safer to handle. Question seven asks for daily evaporation activities. Drying clothes, mopping, boiling water, and sweating are examples. Understanding it helps us dry things faster or stay cool.
[CHECKPOINT]
Question eight asks how water is present in solid state in nature. It exists as glaciers, snow, hailstones, and frost. Question nine asks to reflect on water is our responsibility before it is our right. We must conserve and protect water for future generations and all life, rather than using it selfishly. Question ten asks how to cool a hot two wheeler seat. Sprinkle water on it. Rapid evaporation absorbs heat, cooling the seat quickly. Learning further activities encourage you to wet one hand and blow air across both to feel the cooling effect. You can also make a board game navigating water states and cycle concepts, and act out the water cycle stages in a school assembly through role playing. These activities reinforce your understanding through hands on practice and creative expression. We have covered every concept, activity, experiment, and definition from this chapter. Remember, water changes states through heating and cooling, evaporation and condensation drive the water cycle, and understanding these processes helps us conserve this vital resource. Thank you for listening! Keep revising and practicing. Goodbye! [CHAPTER_COMPLETE]