Biology Chapter 3 Flashcards

Questions and Answers

Why are water molecules polar?

Water molecules are polar because both hydrogen (positive) and oxygen (negative) atoms have opposite charges, making it a polar covalent bond and a polar molecule.

Explain why water molecules are capable of hydrogen bonding with 4 neighboring water molecules.

Because of the atoms in the water molecules. Hydrogen(+) and Oxygen(-) attach and disconnect with other oppositely charged water molecules creating multiple bonds.

What is cohesion?

Cohesion occurs when water molecules bond/form together, since the hydrogen and oxygen atoms are polar they have opposite charges that attract each other.

What is adhesion?

Adhesion works the same way as cohesion on a molecular level; its ability is to reverse the effects of gravity to pull water up, like from the roots of a plant to the top of its leaves. Signup and view all the answers

Why does ice float on water?

Solid ice is able to float on liquid water because it is less dense than its liquid form. Signup and view all the answers

Why is water considered a great solvent?

Water is a great solvent because both of its particles have a positive and negative charge, allowing it to attract ions like sodium and chloride. Signup and view all the answers

How do cohesion and adhesion contribute to the movement of water from the roots to the leaves of a tree?

Cohesion keeps water together, while adhesion allows it to cling to surfaces, pulling water up from roots to leaves during evaporation. Signup and view all the answers

Distinguish between heat and temperature.

Temperature is a measure of the average kinetic energy of molecules, while heat is thermal energy transferred from one body to another. Signup and view all the answers

Match the terms with their definitions: Solute, Solvent, Solution.

Solute = The substance that is dissolved Solvent = The dissolving agent of a solution Solution = A liquid homogeneous mixture of two or more substances Signup and view all the answers

Distinguish between hydrophobic and hydrophilic substances.

Hydrophilic = Water loving; substances that can form bonds with water Hydrophobic = Water hating; substances that repel water Signup and view all the answers

Name the products of the dissociation of water and give their concentration in pure water.

Hydrogen and Hydroxide ions; 10^-7M Signup and view all the answers

Define acid, base, and pH.

Acid: a substance that increases hydrogen ion concentration. Base: a substance that reduces hydrogen ion concentration. pH: a measure of hydrogen ion concentration equal to -log of [H+]. Signup and view all the answers

How do you determine the pH of a solution if the concentration of hydrogen or hydroxide ions is known?

You subtract the given concentration from 14 on the pH scale. Signup and view all the answers

How do acids and bases alter hydrogen ion concentration in a solution?

Acids increase the concentration of hydrogen ions while bases reduce the concentration of hydrogen ions. Signup and view all the answers

What is the function of buffers, and give an example in the human body.

A buffer minimizes changes in concentrations of H+ and OH-; an example is carbonic acid. Signup and view all the answers

Study Notes

Properties of Water

Water molecules are polar due to the positive charge of hydrogen atoms and the negative charge of oxygen atoms, resulting in polar covalent bonds.
Water can form hydrogen bonds with up to four neighboring water molecules because of the attraction between oppositely charged regions.

Cohesion and Adhesion

Cohesion describes the attraction between water molecules, allowing them to form clusters due to polarity.
Adhesion refers to water's ability to cling to other substances, facilitating the upward movement of water in plants against gravity.

Ice and Density

Ice floats on liquid water because its solid form is less dense, an unusual property that allows aquatic life to survive beneath frozen surfaces.

Water as a Solvent

Water's polarity makes it an excellent solvent. It can dissolve ionic compounds like salt by attracting and surrounding sodium and chloride ions.

Water Movement in Plants

Water's cohesion maintains liquid integrity during transport through plant vessels, while adhesion aids in drawing water up from roots to leaves via evaporation.

Heat vs. Temperature

Temperature measures the average kinetic energy of molecules, while heat is the thermal energy transferred between objects.

Solutions and Solutions Components

A solute is a substance dissolved in a solvent. A solution is a homogeneous mixture of solutes and solvents.

Hydrophilic vs. Hydrophobic

Hydrophilic substances, such as cotton, attract water despite not dissolving. Hydrophobic substances, like vegetable oil, repel water and do not mix with it.

Water Dissociation

When water dissociates, it produces hydrogen and hydroxide ions at a concentration of 10^-7 M in pure water.

Acids, Bases, and pH

Acids increase hydrogen ion concentration; bases decrease it. pH measures this concentration, ranging from 0 to 14.

Calculating pH

To determine pH from known hydrogen or hydroxide ion concentrations, subtract the value from 14 on the pH scale.

Role of Acids and Bases

Acids and bases influence hydrogen ion concentration directly through increase or decrease, affecting pH levels.

Function of Buffers

Buffers stabilize pH by minimizing fluctuations in ion concentrations, with carbonic acid serving as a key buffer in the human body.

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Description

Explore the essential concepts of water molecules in this flashcard quiz from Biology Chapter 3. Discover why water is a polar molecule and its unique ability to form hydrogen bonds with neighboring molecules. Perfect for reinforcing your understanding of molecular biology!