Bio 151 - McGraw SB (Ch 2.2-2.5)

Arrange the following states of water in order from most dense to least dense (start with most dense at the top).

liquid solid gas

Select the molecules that tend to be hydrophobic.

Hydrocarbon chains (chains composed entirely of carbon and hydrogen atoms) Nonpolar molecules Oils

Water consists of one oxygen atom joined to two hydrogen atoms by two single, polar _________________ bonds.

covalent

The angle between the two bonds that hold a water molecule together is approximately which of the following?

104.5

A molar concentration of 2 M is equal to:

2 mol/L

The water molecule shown in these two diagrams is held together by which of the following bonds?

Two single polar covalent bonds

When 1 g of sugar is dissolved in 500 mL of water, the sugar is called the___________________ and water is called the ________________________.

aolute, solvent

The ability of water to rise inside a tube of narrow diameter against the pull of gravity is called _________________ action.

capillary

Water consists of one oxygen atom joined to two hydrogen atoms by two single, polar __________________ bonds.

covalent

What does it mean when we say water is adhesive?

It is attracted to other polar molecules and ions.

A hydrogen bond can form between the partially negative ___________________ atom of one water molecule and the partially positive _______________________ atom of another water molecule.

oxygen, hydrogen

A hydrogen ion, formed during the dissociation of water, has a charge of which of the following?

+1

One __________________ of a substance has a weight in grams equal to the combined atomic masses of all atoms that make up one molecule of the substance.

mole

One _______________________ of sucrose contains 6.02 x 1023 __________________ of sucrose.

mole, molecules

Water carries two partial __________________charges on the oxygen atom and two partial _________________charges, one on each hydrogen atom.

negative, positive

If you dissolve 0.05 mol of sugar into 100 ml of water, the result is which of the following?

0.5 M solution of sugar

Hydrophobic substances tend to do which of the following?

Aggregate together when mixed with water in order to minimize contact with water Repel water Assume shapes that minimize contact with water

Why is solid water less dense than liquid water?

As the movement of water molecules slows down when liquid water changes to ice, hydrogen bonds form that space the molecules relatively far apart.

Why does water have very high specific heat?

Because a large input of thermal energy is required to break the many hydrogen bonds between individual water molecules

Water has a high heat of vaporization because it takes a large amount of energy to do which of the following?

Break the hydrogen bonds between different water molecules

Which of the following molecules is likely to have the highest specific heat and the highest heat of vaporization?

H2O

The amount of energy required to change 1 g of a substance from a liquid to a gas is called which of the following?

Heat of vaporization

What is the temperature of a substance a measure of?

How fast its molecules are moving

Consider a large protein molecule that has some parts that are highly hydrophobic. When placed in a water solution, the protein folds in a globular shape, such that all the hydrophobic portions are inside the molecules, away from water. This is an example of which of the following?

Hydrophobic exclusion

Which of the following occurs because solid water is less dense than liquid water (choose all that apply)?

Ice floats. Bodies of water freeze from the top down. Aquatic organisms can survive in liquid water below the frozen surface of ponds and lakes.

How does water's high specific heat affect living organisms?

It helps prevent organisms from overheating due to the thermal energy released by chemical reactions inside cells. It helps organisms maintain a relatively stable internal temperature when the external temperature rises or falls.

How does water's high heat of vaporization affect living organisms?

Many organisms sweat or pant in order to cool themselves. When your body is wet, you feel cooler than when your body is dry.

Compared to covalent bonds, hydrogen bonds are which of the following?

Much weaker

Water tends to repel or exclude which of the following?

Nonpolar molecules Hydrophobic molecules

A single water molecule can spontaneously break apart (ionize) to form which of the following?

One positive hydrogen ion and one negative hydroxide ion

Select the molecules that tend to be hydrophilic.

Polar molecules Ions

Which of the following is the definition of the heat of vaporization of water?

The amount of energy needed to change 1 g of water from a liquid to a gas

The surface tension of water is due to which of the following?

The cohesion of water molecules

During capillary action, the water will rise higher in which situation?

The narrower the capillary tube is

Why does water rise inside a glass tube with a narrow diameter (a capillary)?

There are electrical charges on the surface of the glass.

Which of the following describes hydrogen bonds?

They are about 5 - 10% as strong as covalent bonds.

Water is cohesive. Which describes this feature of water molecules?

They are attracted to each other.

Hydrogen bonds are important for which reasons?

They help maintain the structure of DNA and proteins. They play a key role in determining the properties of water.

Which of the following accurately describes the cause of the high surface tension of water?

Water molecules attract each other.

How is the arrangement of water molecules related to its density?

Water molecules in ice are locked into a crystal-like lattice due to hydrogen bonds, making ice less dense than liquid.

The evaporation of water from body surfaces can significantly cool an organism. This is due to what property of water?

Water's high heat of vaporization

Water helps living things maintain a relatively constant internal temperature and protects cells from overheating due to the heat released by chemical reactions. What property of water is responsible for that?

Water's high specific heat

When a sugar crystal is placed in water, every time a sucrose molecule dissociates from the crystal, water molecules surround it in a cloud forming a(n) ___________________ shell that prevents it from associating with other sucrose molecules.

hydration

The relatively weak, but numerous _________________________ bonds that form between a water molecule and other molecules (including other water molecules) play a key role in determining the properties of water (please spell the name of the bonds, no abbreviations).

hydrogen

Water has a high specific heat because a large input of thermal energy is needed to break the many________________ that restrict the movement of individual water molecules.

hydrogen bonds

Substances that attract water are called ______________________("water-loving") while substances that repel water are called _____________________("water-fearing").

hydrophilic, hydrophobic

The tendency of nonpolar molecules to aggregate together in water is known as __________________ exclusion.

hydrophobic

Fish and other animals can survive at the bottom of a lake during winter because ice is _________________ dense than liquid water.

less

Solid water is ___________ dense than liquid water.

less

The amount of heat 1 g of a substance must absorb or lose to change its temperature by 1°C is called __________________.

specific heat

Because of the many hydrogen bonds that form between its molecules, water has a very high _________________ . This allows small insects to "walk on water."

surface tension

The _______________________________ of a substance is a measure of how rapidly its individual molecules are moving.

temperature

A(n) _________________ molecule can break apart to form a positive hydrogen ion and a negative hydroxide ion.

water

A(n) ____________________________ molecule can break apart to form a positive hydrogen ion and a negative hydroxide ion.

water