Chapter 3 campbell biology

What is the primary substance that makes life possible on Earth?

Water.

What percentage of most cells is made up of water?

70-95% water.

What kind of bonds do water molecules form due to their polarity?

Hydrogen bonds.

Define cohesion in terms of water molecules.

Cohesion is the attraction between water molecules that allows them to stick together.

What is the specific heat of water in cal/g/°C?

1 cal/g/°C.

What is evaporative cooling?

The process by which the evaporation of a liquid cools the remaining liquid.

At what temperature does water freeze at sea level?

0°C.

What is a mole in chemistry?

A mole is the amount of substance that contains 6.02 × 10^23 molecules.

What does the pH scale measure?

The acidity or basicity of a solution.

What is an acid?

A substance that increases the hydrogen ion concentration in a solution.

Define a buffer in biological terms.

A buffer is a solution that resists changes in pH when acids or bases are added.

What is the heat of vaporization for water?

About 580 cal for 1 g of water.

What phenomenon allows ice to float on water?

Ice is less dense than liquid water.

What term refers to substances that fear water and do not dissolve in it?

Hydrophobic.

What is the interaction between Na+ ions and water molecules called when salt is dissolved in water?

Hydration shell.

What does a strong acid do in solution?

Dissociates completely to increase H+ concentration.

What is the outcome when acid precipitation occurs?

Rain, snow, or fog with a pH less than 5.6.

What is the difference between strong and weak acids?

Strong acids dissociate completely, while weak acids do so reversibly.

What is a hydrophilic substance?

A substance that has an affinity for water.

What is the relationship between temperature and molecular kinetic energy?

As temperature increases, the average kinetic energy of molecules increases.

What is the role of buffers in biological fluids?

Buffers maintain a stable pH by accepting or donating hydrogen ions.

What effect does acid rain have on aquatic ecosystems?

It affects the early developmental stages of aquatic organisms.

What happens to the hydrogen ion concentration in a basic solution?

It is lower than that of hydroxide ions.

What must occur for a water molecule to evaporate?

It must absorb enough heat to overcome the attraction of other molecules.

What is the significance of the unique properties of water for life?

These properties enable processes essential for survival, such as temperature moderation and nutrient transport.