Chapter 2: The Nature of Molecules and the Properties of Water

Flashcards covering the fundamental concepts of atoms, chemical bonds, properties of water, and acids/bases, based on the provided Biology lecture notes.

What is all matter composed of?

Atoms

What did the Rutherford Scattering Experiment reveal about the atom's structure?

It proposed the existence of a very small central region containing positive charge (the nucleus) surrounded by electrons.

What are the three main subatomic particles and their charges?

Protons (positively charged), Neutrons (neutral), and Electrons (negatively charged).

Where are protons and neutrons located in an atom?

In the nucleus.

Where are electrons located in an atom?

In orbitals surrounding the nucleus.

In a neutral atom, how does the number of protons compare to the number of electrons?

The number of protons equals the number of electrons.

What defines an element's atomic number?

The number of protons.

What is an element?

Any substance that cannot be broken down to any other substance by ordinary chemical means.

How is an atom's atomic mass determined?

It is the sum of its protons and neutrons.

What is the approximate mass of a proton or neutron?

Approximately 1 Dalton.

What is a cation?

A charged particle with more protons than electrons, resulting in a net positive charge.

What is an anion?

A charged particle with fewer protons than electrons, resulting in a net negative charge.

What are isotopes?

Atoms of a single element that possess different numbers of neutrons.

In the context of radioactive isotopes, what is a 'half-life'?

The time it takes for one-half of the atoms in a sample to decay.

What is key to understanding the chemical behavior of an atom?

The number and arrangement of its electrons in their orbitals.

According to modern physics, what is an orbital?

An area around a nucleus where an electron is most likely to be found.

How does an electron's distance from the nucleus affect its energy?

Electrons farther from the nucleus have more potential energy.

What is 'oxidation' in a chemical reaction?

The loss of an electron.

What is 'reduction' in a chemical reaction?

The gain of an electron.

What are valence electrons?

The number of electrons in the outermost energy level of an atom.

What is the 'octet rule'?

Atoms tend to establish completely full outer energy levels, typically with eight electrons (with an exception for elements like Helium needing only two).

What four elements make up 96.3% of human body weight?

Carbon, hydrogen, oxygen, and nitrogen.

What is a molecule?

A group of atoms held together in a stable association.

What is a compound?

A molecule containing more than one type of element.

How are ionic bonds formed?

By the attraction of oppositely charged ions, which result from the gain or loss of electrons.

How are covalent bonds formed?

When atoms share two or more valence electrons.

What is electronegativity?

An atom's affinity for electrons.

What is the key difference between nonpolar and polar covalent bonds?

Nonpolar covalent bonds involve equal sharing of electrons, while polar covalent bonds involve unequal sharing of electrons.

In chemical reactions, what are 'reactants' and 'products'?

Reactants are the original molecules, and products are the molecules resulting from the reaction.

What three factors primarily influence the extent of a chemical reaction?

Temperature, concentration of reactants and products, and catalysts.

What is the single most outstanding chemical property of water?

Its ability to form hydrogen bonds.

What are hydrogen bonds in the context of water molecules?

Weak chemical associations that form between the partially negative oxygen atoms and the partially positive hydrogen atoms of two water molecules.

Why is water considered a polar molecule?

Oxygen is much more electronegative than hydrogen, leading to partial negative charges on oxygen and partial positive charges on hydrogen atoms.

What is cohesion when referring to water?

The attraction of water molecules to other water molecules by hydrogen bonding.

Distinguish between cohesion and adhesion.

Cohesion is when water molecules stick to other water molecules, while adhesion is when water molecules stick to other polar molecules.

Name three important properties of water.

High specific heat, high heat of vaporization, and solid water being less dense than liquid water.

What is the significance of water having a high specific heat?

A large amount of energy is required to change the temperature of water.

What is the biological significance of solid water being less dense than liquid water?

Bodies of water freeze from the top down, allowing aquatic life to persist beneath the ice.

Why is water considered a good solvent?

Polar molecules and ions are soluble in water.

What is the difference between hydrophilic and hydrophobic molecules?

Hydrophilic molecules are 'water-loving' and soluble in water, while hydrophobic molecules are 'water-fearing' and tend to aggregate in water.

What does pH measure?

The negative logarithm of the hydrogen ion concentration of a solution.

What is the pH of pure water, and what does it signify?

pH = 7, signifying that it is neutral (neither acidic nor basic).

What is an acid?

Any substance that dissociates in water to increase the hydrogen ion concentration (and lower the pH).

What is a base?

A substance that combines with hydrogen ions dissolved in water, thereby lowering the hydrogen ion concentration and raising the pH.

What is the primary function of a buffer?

To resist changes in pH.

How do buffers maintain a relatively constant pH?

They release hydrogen ions when a base is added and absorb hydrogen ions when an acid is added.