Properties of Water

Summary

This transcript by the Amoeba Sisters delves into the intriguing properties of water, highlighting why it's a remarkable molecule essential for life. They explain water's polar nature, hydrogen bonding, and its capabilities like cohesion, adhesion, and high specific heat. Through simple anecdotes and explanations, the sisters explore how these properties support biological functions, including how they enable trees to draw water against gravity, allow insects to walk on water, and provide stability in aquatic environments. Additionally, they discuss water’s role as a powerful solvent and its unique behavior when freezing, which is critical for aquatic life.

Highlights

• Water, a polar molecule, is crucial due to its shape and bonding capabilities. 🌊
• Hydrogen bonds in water lead to cohesive and adhesive properties. 🤝
• Water's high specific heat helps it maintain stable temperatures in aquatic environments. 🌡️
• When water freezes, it expands, creating less dense ice, essential for aquatic ecosystems. ❄️
• Being an excellent solvent, water plays a significant role in biological activities. 🧪

Key Takeaways

• Water is polar and shaped like a V, leading to amazing properties! 🌊
• Hydrogen bonding allows water to bond easily with other molecules, aiding cohesion and adhesion. 🤝
• Water's high specific heat stabilizes temperatures, vital for aquatic environments. 🌡️
• Water expands upon freezing, forming ice that floats, crucial for aquatic life. ❄️
• It’s a powerful solvent, dissolving many molecules, key for biological processes. 🧪

Overview

Water, the Amoeba Sisters' favorite molecule, is a marvel in biology due to its unique properties. At the core, water’s V-like shape and polarity create the perfect conditions for hydrogen bonding. These bonds lead to cohesion, making it possible for water to form droplets and resist external forces. It's this very cohesion that allows water striders to effortlessly glide across its surface. Meanwhile, adhesion lets water climb up plant vessels, defying gravity in a show of botanical wonder.

High specific heat is another of water’s impressive traits. It allows water to absorb significant amounts of heat without drastic changes in temperature, ensuring stable aquatic environments. This property also contributes to the cooling effects observed in animals and plants through evaporation, helping them regulate during hot conditions. And while the sun blazes down, water’s heat remains tempered, releasing it gradually as seasons shift. Water’s thermal properties are like nature’s own thermostat.

Most astonishingly, unlike most substances, water expands when it freezes. This quirky phase transition results in ice that floats, forming an insulating layer that protects aquatic life in cold conditions. Add to this its prowess as a solvent, dissolving numerous substances, and you see why water is indispensable in countless biological processes. The Amoeba Sisters’ exploration reveals water’s multifaceted role in life on Earth, from nurturing life in ponds to maintaining global climate stability.

Chapters

• 00:00 - 00:30: Introduction to Water The chapter introduces water, describing it as a polar molecule shaped like an outstretched V, with several remarkable properties. It makes up 75% of the Earth's surface, which is a key identifying feature. The narrative uses playful riddles to engage the audience while discussing the importance of water.
• 00:30 - 01:00: The Polarity of Water This chapter delves into the unique properties of water and its fundamental role in biology. It emphasizes the shape of water molecules and their polarity. The molecule consists of a highly electronegative oxygen atom that attracts electrons more than the hydrogen atoms it is bonded with, resulting in a partial negative charge on the oxygen. These characteristics highlight the distinct features of water important for biological functions.
• 01:00 - 01:30: Hydrogen Bonds and Water's Unique Properties The chapter discusses the unique properties of water due to hydrogen bonds. It explains how the polarity of water molecules, with oxygen being slightly negative and hydrogen slightly positive, enables them to bond easily. These bonds, known as hydrogen bonds, are critical for the various characteristics and behaviors of water.
• 01:30 - 02:30: Water's Adhesion and Cohesion The chapter explores the concepts of water adhesion and cohesion, particularly in relation to how water travels up tall trees. Despite gravity, water is transported to the top through the plant's xylem vessels. Water adheres to the xylem walls, a property known as adhesion, which assists in defying gravity.
• 02:30 - 03:00: Cohesion and Surface Tension The chapter explains the concept of cohesion among water molecules, facilitated by hydrogen bonding. This cohesive property is likened to 'beads on a string,' where evaporating water molecules pull up the next in line. Additionally, cohesion contributes to the ability of certain insects, like water striders, to walk on water.
• 03:00 - 03:30: Water as a Solvent In the chapter titled 'Water as a Solvent,' the discussion focuses on the unique properties of water, particularly its surface tension, which is higher compared to other liquids. This property is due to cohesion and allows various organisms, from insects to larger animals, to walk on water. The chapter also highlights water's polarity, making it an effective solvent for other molecules, emphasizing its importance in various chemical and biological processes.
• 03:30 - 05:00: The Density of Ice vs. Water The chapter discusses the solvent properties of water, emphasizing its ability to dissolve polar molecules and ionic compounds. This characteristic is crucial for various biological processes, as water serves as a solvent in many bodily functions, such as kidney filtration and other body fluids. Additionally, the chapter includes a personal anecdote about the author's father building a pond for goldfish, highlighting a memory related to the water theme.
• 05:00 - 06:30: Water's High Specific Heat The chapter discusses the experience of observing a pond in West Texas that freezes in the winter. Despite the top layer of the pond freezing, the fish underneath continue to swim and live normally. This occurrence is tied to the unique property of water's high specific heat and its behavior when freezing.
• 06:30 - 07:30: Evaporative Cooling The chapter discusses the unique property of water where it expands upon freezing, making it less dense than its liquid form. This causes ice to float, forming an insulated surface layer on bodies of water. This phenomenon is crucial for the survival of many organisms. The behavior is attributed to the hydrogen bonds in water. At freezing temperatures, these hydrogen bonds do not break and reform as frequently, and the water molecules settle into a lattice structure that keeps them just far enough apart to create this effect.
• 07:30 - 08:00: Conclusion This chapter discusses the important physical properties of water that affect aquatic life. One significant characteristic is that ice is less dense than liquid water, allowing ice to float and creating a stable environment for aquatic organisms during cold periods. Another crucial property is water's high specific heat, which means it can absorb or lose significant amounts of heat without drastically changing temperature. This property helps moderate Earth's climate and provides a stable environment for aquatic life.

Properties of Water Transcription

• 00:00 - 00:30 Captions are on! Click CC at bottom right to turn off. Follow us on Twitter (@AmoebaSisters) and Facebook! We have a riddle for you. Ok, not really a riddle. We’re bad at riddles. More like clues about our favorite molecule. It’s polar. It’s shaped like an outstretched V. Its properties are awesome. We have a riddle for you. Ok, not really a riddle. We’re bad at riddles. More like clues about our favorite molecule. It’s polar. It’s shaped like an outstretched V. Its properties are awesome. Also, it makes up ¾ of the Earth’s surface. That one always gives it away. Our favorite molecule is water.
• 00:30 - 01:00 And we’re not going to lecture you about how important water is and the fact that all life as we know it could not survive without it, because yeah that’s true, but we really want to talk about what makes water so unique for biology itself. What are these awesome properties? We mentioned the shape of water and the fact that it is polar. It has one very electronegative oxygen that is always trying to keep the electrons closer to it than to the hydrogens it is bonded to. This actually gives the oxygen a slightly negative charge---because of the electrons
• 01:00 - 01:30 that are spending more time next to it---and it gives the hydrogens a slightly positive charge. Well that means that other water molecules have an easy time bonding together. Why? Because the hydrogen of one water molecule with its slightly positive charge can bond to another water molecule’s oxygen with a slightly negative charge. These bonds among the water molecules are hydrogen bonds, and these very bonds are what allow water to do these things
• 01:30 - 02:00 that it can do…which we are about to talk about. Have you ever looked at a really tall tree and wondered, “How does the water get all the way up there?” I mean, it’s got to go against gravity. Gravity! Well in our plant video, we talk about the xylem. It’s vessels within certain types of plants, like trees, that transports water. But what’s really neat about water is that---it sticks to the xylem walls in what is known as adhesion. This helps fight gravity. But water molecules,
• 02:00 - 02:30 with their hydrogen bonding, also bond to each other in something called cohesion. In almost a “beads on a string” kind of fashion, as water molecules evaporate from a leaf---the next water molecule in line is pulled upwards and so on. Cohesion is also a reason that water striders, one of our favorite insects, can skate on
• 02:30 - 03:00 water. Cohesion contributes to the surface tension of water. Water actually has quite a bit of surface tension compared to other liquids. And it’s not just water striders. There are a lot of insects, spiders, and even larger animals like reptiles and birds that can walk on water. So to the Google for that. With water being polar, it also is a powerful solvent for other molecules. That means that
• 03:00 - 03:30 water can dissolve many other molecules especially polar molecules and ionic compounds. Why does that matter? This is important because many of the processes occurring in organisms use water as a solvent. Just consider the need for water for your kidneys in their filtering properties and all different types of body fluids. I’ll never forget when I was little, my father built us a pond. We had some goldfish
• 03:30 - 04:00 in there. We loved our pond. Well in West Texas where we’re from---it can freeze in the winter. And one morning I went outside, terrified, to find that the top of my pond had frozen. I thought my fish were goners. Only to find them swimming and doing their…fish activities…under the ice layer. See most substances actually contract when they freeze
• 04:00 - 04:30 and become more dense. But water expands when it freezes and becomes less dense when frozen. Resulting in floating ice where it can actually make an insulated surface layer that makes a difference for many organisms. This is due to the hydrogen bonds. At freezing level, the breaking and reforming of hydrogen bonds---which is usually happening often---is not happening very much. The molecules are set into a lattice of hydrogen bonded molecules just far enough
• 04:30 - 05:00 apart that it is less dense in ice form than in water form. That is all going to be very important for aquatic life. Speaking of temperature, water resists changing its temperature. It has what is called a high specific heat. Specific heat is a measurement of heat that needs to be absorbed or lost for 1 g of a substance to change its temperature by 1C. That’s why, on the first day that
• 05:00 - 05:30 school is out in the summer, it may be super hot outside but the water can still be pretty cold. It’s really good that water is like this for life---it is stabilizing for aquatic environment temperatures. It also means that water can absorb a lot of heat in the summer without reaching as high of temperatures itself---which is useful when the winter comes along. The water can release heat as it cools in the winter. Still on the topic of temperature, consider evaporation. Many animals rely on evaporation
• 05:30 - 06:00 to cool them. Think of water molecules. They are moving, but those that have more energy---are “hotter” per se---are moving the fastest. They are more likely to make the phase change to gas. As these molecules leave, their energy---their heat---is no longer on your skin. By the way, all of this is not just animals too. Plants use evaporative cooling to aid them in hot
• 06:00 - 06:30 temperatures. Excessive high temperatures can be dangerous for many different processes in both plants and animals---it can be damaging to the enzymes in many of those processes. Well we went through a lot of features of water---definitely something to consider next time you encounter it. Which based on how much we depend on it…will likely be soon. Well that’s it for the Amoeba Sisters and we remind you to stay curious.