Chemistry 15 pretest

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How does the surface tension of water compare with the surface tension of most other liquids?

Water's surface tension is higher than most.
What effect does a wetting agent (Surfactant) have on surface tension?

A surfactant is any substance that interferes with the hydrogen bonding between water molecules and thereby reduces surface tension.
What is the shape of the water molecule?

The molecule has a bent shape between oxygen and hydrogen.
What is the bond angle of a water molecule?

Approximately 105°
What force holds water molecules together in the liquid state?

Covalent bonds
Which atom in a water molecule is more of electronegative?

Oxygen
What are the bonds between adjacent water molecules called?

Hydrogen bonds
What causes Brownian motion in the colloidal suspensions?

Collisions of the molecules of the dispersion medium with the small, dispersed colloidal particles
What is an emulsion?
- A colloidal dispersion of a liquid in a liquid.
- For example oil will mix with water in the presence of soap
What does an emulsifying agent typically have?

One end is just polar and is attracted to water molecules, and the other end is nonpolar and soluble in oil or grease
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Which types of compounds are soluble in water?
- Ionic compounds
- Polar covalent molecules
Which type of compounds are soluble in a nonpolar solvent like C6H6?

Nonpolar covalent molecules
Which type of compounds form electrolytes?

Ionic compounds
How do you recognize compounds that form electrolytes?
- They dissolve in water
- They conduct an electric current in an aqueous solution
Which type of compounds form non-electrolytes?

Compounds that do not have ions
How do you recognize a nonelectrolyte?

It doesn't conduct an electric current in a solution
What type of compound is always an electrolyte when dissolved?

Ionic compounds
What is an electrolyte?

A compound that conducts an electric current when it is in an aqueous solution or in the molten state
What do we call a crystal that absorbs water vapor from the air?

Hygroscopic hydrates
What do we call a crystal that has a water vapor pressure greater than the water vapor pressure of the air?

Efflorescent hydrates
What do we call a crystal that absorbs water from the air and dissolves in the water?

Deliquescent compounds
Which type of mixture is characterized by the settling of particles?

Suspension
What is a colloid?

A heterogeneous mixture containing particles that range in size from 1 nm to 1000 nm
List for colloids from your book.
- Whipped cream
- Marshmallow
- Mayonnaise
- Paint
Which two types of mixtures except that the Tyndall effect?

Suspensions and colloids
How does a surfactant reduce surface tension?

The surfactant interferes with the hydrogen bonding between water molecules
At what temperature does liquid water have its maximum density?

4°C
Water has a high heat capacity. Does the temperature water change rapidly when exposed to solar energy?

Heat capacity and latent heat are key properties that allow water (the oceans in particular) to play a major role in "regulating" Earth's climate. Water absorbs solar energy and releases it slowly; thus, larger bodies of water do not change temperature rapidly.
Water has a high heat of vaporization. Does this make temperature extremes on earth greater than expected, less than expected or is there no effect?

Temperature extremes on earth are less than expected because water buffers the large fluctuations in temperature
What is responsible for water's high boiling point?

Extra heat is needed to break the hydrogen bonds between water molecules
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In a solution, what is the dissolving medium?

Solvent
What is a solution?

A homogenous mixture; consists of solutes dissolved in a solvent

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Chemistry 15 pretest

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Chemistry 15 pretest

Updated

3/9/2014, 1:01:35 AM

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