The Mickey Mouse Molecule! Hydrogen Hydrogen Oxygen
Structure of a Water Molecule • Water is polar. • A polar molecule is a molecule that has an electrical charge. • Water is made of: • 2 Hydrogen Atoms and 1 Oxygen atom. • The chemical formula for water is:H2O • Hydrogen has a positive (+) charge and Oxygen has a negative (-) charge.
4 Key Properties of Water • Capillary Action • Surface Tension • Universal Solvent • Specific Heat
Capillary Action • Capillary action is the combined force of attraction among water molecules and with the molecules of surrounding materials. • Examples of Capillary Action of Water: • Liquid rising inside a straw • Paper towel absorbing water • Wet jeans • Plant roots absorbing water • Sponge
Surface Tension • Surface tension is the tightness across the surface of water that is caused by the polar molecules pulling on one another • Examples of the surface tension of water: • Raindrops forming beads on surface • Water strider • Paperclip Floating on Water • Drops of Water on a Penny • Skipping Rocks • Meniscus • Belly Flops
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Universal Solvent • Solution: A mixture that forms when one substance dissolves another. • Solvent: substance that does the dissolving. • Solute: substance that gets dissolved. • Water is the universal solvent because it dissolves so many substances because of its high polarity. • Water can dissolve substances such as salt and sugar but cannot dissolve oil. - Polar Dissolves Polar.
Specific Heat • Water requires a lot of heat (gain or loss) to change its temperature due to the strong attraction among water molecules. • Specific heat is the amount of heat needed to increase the temperature of a substance by 10C • Example of specific heat: - Water temperature vs. sand temperature at the beach during the day.
Why does water have a high specific heat? • Water’s high specific heat is due to thestrong attraction among water molecules. • The molecules arestuck togetherand it takesa lot of energyto break the strong bonds of the water molecules.
Changing State • Water exists in 3 forms: • solid • liquid • gas solid liquid gas
Molecule Movement Molecules move the slowest in a solid. • Solid-molecules are close together Molecules move the fastest in a gas. • Gas-molecules move freely; they are spread apart
Phase Changes • Melting-water changes from a solid to a liquid • Example: Ice melts into water • Freezing-water changes from a liquid to a solid • Example: Water freezes into ice Melting Solid Liquid Freezing
Phase Changes • Evaporation- process by which molecules at the surface of a liquid absorb enough energy to change to the gaseous state • Example: boiling water, hair air-drying, wet clothes drying on a clothesline outside, puddle drying up • Condensation-process by which a gas changes to a liquid • Example: water droplets on the outside of a glass fogging up a window Evaporation Gas Liquid Condensation