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Water has a high specific heat due to the hydrogen bonding between water molecules. Study with Quizlet and memorize flashcards containing terms like Part A - Hydrogen bonding Label the following diagram of water molecules, indicating the location of bonds and the partial charges on the atoms.
- Overview
- Introduction
- Water: Solid, liquid, and gas
- Density of ice and water
- Heat capacity of water
- Heat of vaporization of water
Specific heat capacity and heat of vaporization of water. Evaporative cooling. Why ice floats.
Let’s imagine that it’s a hot day. You’ve just been out in the sun for awhile, and you’re sweating quite a bit as you sit down and grab a glass of cool ice water. You idly notice both the sweat beads on your arms and the chunks of ice floating at the top of your water glass. Thanks to your hard work studying the properties of water, you recognize both the sweat on your arms and the floating ice cubes in your glass as examples of water's amazing capacity for hydrogen bonding.
How does that work? Water molecules are very good at forming hydrogen bonds, weak associations between the partially positive and partially negative ends of the molecules. Hydrogen bonding explains both the effectiveness of evaporative cooling (why sweating cools you off) and the low density of ice (why ice floats).
Water has unique chemical characteristics in all three states—solid, liquid, and gas—thanks to the ability of its molecules to hydrogen bond with one another. Since living things, from human beings to bacteria, have a high water content, understanding the unique chemical features of water in its three states is key to biology.
In liquid water, hydrogen bonds are constantly being formed and broken as the water molecules slide past each other. The breaking of these bonds is caused by the energy of motion (kinetic energy) of the water molecules due to the heat contained in the system.
When the heat is raised (for instance, as water is boiled), the higher kinetic energy of the water molecules causes the hydrogen bonds to break completely and allows water molecules to escape into the air as gas. We observe this gas as water vapor or steam.
On the other hand, when the temperature drops and water freezes, water molecules form a crystal structure maintained by hydrogen bonding (as there is too little heat energy left to break the hydrogen bonds). This structure makes ice less dense than liquid water.
Water’s lower density in its solid form is due to the way hydrogen bonds are oriented as it freezes. Specifically, in ice, the water molecules are pushed farther apart than they are in liquid water.
That means water expands when it freezes. You may have seen this for yourself if you've ever put a sealed glass container containing a mostly-watery food (soup, soda, etc.) into the freezer, only to have it crack or explode as the liquid water inside froze and expanded.
With most other liquids, solidification—which occurs when the temperature drops and kinetic (motion) energy of molecules is reduced—allows molecules to pack more tightly than in liquid form, giving the solid a greater density than the liquid. Water is an anomaly (that is, a weird standout) in its lower density as a solid.
Because it is less dense, ice floats on the surface of liquid water, as we see for an iceberg or the ice cubes in a glass of iced tea. In lakes and ponds, a layer of ice forms on top of the liquid water, creating an insulating barrier that protects the animals and plant life in the pond below from freezing.
It takes a lot of heat to increase the temperature of liquid water because some of the heat must be used to break hydrogen bonds between the molecules. In other words, water has a high specific heat capacity, which is defined as the amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius. The amount of heat needed to raise the temperature of 1 g water by 1 °C is has its own name, the calorie.
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Just as it takes a lot of heat to increase the temperature of liquid water, it also takes an unusual amount of heat to vaporize a given amount of water, because hydrogen bonds must be broken in order for the molecules to fly off as gas. That is, water has a high heat of vaporization, the amount of energy needed to change one gram of a liquid substance to a gas at constant temperature.
Water’s heat of vaporization is around 540 cal/g at 100 °C, water's boiling point. Note that some molecules of water – ones that happen to have high kinetic energy – will escape from the surface of the water even at lower temperatures.
As water molecules evaporate, the surface they evaporate from gets cooler, a process called evaporative cooling. This is because the molecules with the highest kinetic energy are lost to evaporation (see the video on evaporative cooling for more info). In humans and other organisms, the evaporation of sweat, which is about 99% water, cools the body to maintain a steady temperature.
[Attribution and references]
Sep 24, 2021 · Water’s high heat capacity is a property caused by hydrogen bonding among the water molecules. Specific heat is defined as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius.
Specific heat, heat of vaporization, and density of water: Water has a high heat capacity and heat of vaporization, and ice—solid water—is less dense than liquid water. Water owes these unique properties to the polarity of its molecules and, specifically, to their ability to form hydrogen bonds with each other and with other molecules.
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Nov 13, 2022 · Hydrogen bonding between different parts of the same chain (intramolecular bonding; Hydrogen bonding of water molecules to –OH groups on the polymer chain ("bound water") that helps maintain the shape of the polymer. The examples that follow are representative of several types of biopolymers.
There are 3 different forms of water, or H 2 O: solid (ice), liquid (water), and gas (steam). Because water seems so ubiquitous, many people are unaware of the unusual and unique properties of water, including: Boiling Point and Freezing Point; Surface Tension, Heat of Vaporization, and Vapor Pressure; Viscosity and Cohesion; Solid State ...
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As a result of the network of hydrogen bonding present between water molecules, a high input of energy is required to transform one gram of liquid water into water vapor, an energy requirement called the heat of vaporization. Water has a heat of vaporization value of 40.65 kJ/mol.
