Thermal Properties Of water

Phase changes of water and energy When water is in its liquid form, it is capable of absorbing high amounts of energy without changing phase Water molecules in liquid phase interact with each by forming Hydrogen bonds-but individual bonds only last for a few moments As long as water molecules are free to move, they will do so

Removing energy from a system When energy is removed, speed of particles decrease This results in water molecules forming more long-term Hydrogen Bonds to other water molecules Because the electrons in orbitals are mutually-repelling, and the spatial arrangement of these bonds is tetrahedral, water forms highly-ordered crystal structures when in a low energy state

Ice

Ice and Density Ice is less dense than liquid water This is because the Hydrogen bonds that form between molecules in ice hold the individual molecules from each other at a distance that is greater than they’d be at in liquid phase So ice floats (anything less dense than water floats on water—duh!)

Adding energy to the system Increasing the free-energy level in a system causes the particles within the system to move with faster and faster velocities In this case, water molecules begin moving too quickly to interact with each other As they move faster and faster, the total number of molecules occupies more space Steam, clouds, fog, your breath on a cold day are water molecules in gas phase

Review-bonding and energy High energy water molecules exist as steam. They release that energy by forming bonds with other water molecules Water in liquid phase transitions to solid phase as energy is removed Bond formation is energy releasing Ice requires the input of energy to become a liquid Water transitions to steam as more energy is put in Bond breaking is energy consuming

Changes to energy and room to move

Heat capacity of water It takes considerable energy to change the phase of water This energy is measured in calories (the amount of energy it takes to raise one mL of water by 1 degree Celsius) Because of this, sudden drops below freezing do not cause large bodies of water to freeze, for example On a continental scale…

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