Chemistry-Water and its properties

Surface Tension

The inward force that tried to minimize the surface area of a liquid. H-Bonds!

Surfactant

When a wetting agent interferes and breaks down the surface tension, known as a surface-active agent.

Aqueous Solution

Water that contains dissolved substances

Solvent

The dissolving substance in the solution

Solute

The dissolved particles in the solution

Solvation

Solute dissolves and separates into ions - ions are surrounded by the oppositely charges ions of water. (THINK DIAGRAM)

Electrolyte

A compound that conducts electricity when aqueous/molten. (Ex. All ionic compounds, Polar, NaCl, S, Cu..)

Non-Electrolyte

A compound that does not conduct electricity when aqueous or molten. (Ex. C, Nonpolar, starch, sugar..)

Hydrate

Compound that contains water of hydration. (Water from a crystal)

Efflorescent

Hydrate that releases water to the air. Vapor pressure is higher than water vapor pressure.

Hygroscopic

Hydrate that absorbs water from the air. Pressure is lower than water vapor pressure.

Desiccants

“Drying agent,” Absorbs moisture from the air

Deliquescent

Hydrate that absorbs so much water from the air that they liquify.

Suspension

Hetero mixture where particles settle out upon standing. Much larger - do not stay suspended indefinitely.

Colloid

Hetero mixture with particles ranging in size and spread throughout dispersion medium. Particles are ‘medium’ sized.

Solution

Homo mixture where particles do not settle, can not be seperated and are ‘small’

Tyndall Effect

The scattering of light by colloidal particles

Brownian Motion

The random motion of (colloidal) particles. Caused by collision of molecules - prevents particles from settling.

Emulsion

Colloid of a liquid dispersed in a liquid - allows to liquids to mix together. (Ex. Mayo9)

Explain why the following statement is true: Water becomes cooler when some of it evaporates.

The higher (hotter) energy particles are escaping as vapor

Explain why the following statement is true: Different liquids have different vapor pressures at the same temperature.

Liquids have different strengths of attractive forces.

Explain why the following statement is true: Water has an unusually high boiling point considering that it has a low molar mass.

H-Bonding is a very strong attractive force

Explain why the following statement is true: A lake freezes from the top rather than from the bottom.

Ice is less dense than liquid water, so it rises to the top.

Explain why the following statement is true: Water expands when it freezes.

H-bonding creates an open framework of crystals.

Explain why the following statement is true: Some insects with a density greater than water can walk on water.

Surface tension

Explain why the following statement is true: On very cold nights farmers often put tubs of water in storage areas for fruits and vegetables.

Water has high heat capacity, so it releases heat into colder air.

Explain why the following statement is true: A meal can be cooked faster in a pressure cooker than in an open kettle.

Higher pressure = Higher boiling point

Explain why the following statement is true: Ice disappears on a cold winter day when the temperature remains below the freezing point of water.

Sublimation (Goes straight from solid --> gas)

Explain why the following statement is true: Water can be made to boil at 60\*C

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By lowering the air pressure.

Explain why the following statement is true: The boiling point of a liquid is always expressed along with the atmospheric pressure, but the freezing point is not.

Boiling point involves gases which are affected by the pressure. Freezing point involves solids that don't change w/ pressure.

Explain why the following statement is true: Water that seeps into tiny crevices of a rock may cause further cracking when the temperature falls below 0\*C.

Water expands as it freezes due to H-Bonding