Study Guide/Objectives for Chapter 2: Chemistry

What is a simplified model of an atom?

An atom has a nucleus with protons and neutrons, with electrons moving in orbitals around it.

What is an element?

An element is a substance made of only one type of atom.

What is a compound?

A compound is made of two or more different elements chemically bonded.

What is a proton?

A proton is a positively charged particle in the nucleus.

What is a neutron?

A neutron is a neutral particle in the nucleus.

What is an electron?

An electron is a negatively charged particle outside the nucleus.

What is atomic number?

Atomic number is the number of protons in an atom.

What is mass number?

Mass number is the total number of protons and neutrons.

What is a covalent bond?

A covalent bond forms when atoms share electrons.

What is an ionic bond?

An ionic bond forms when electrons are transferred between atoms, creating ions.

What is a hydrogen bond?

A hydrogen bond is a weak attraction between a hydrogen and an electronegative atom.

What is an isotope?

An isotope is an atom of the same element with different numbers of neutrons.

What is an ion?

An ion is an atom that has gained or lost electrons and has a charge.

How are atomic number, mass number, and neutrons related?

Mass number equals protons plus neutrons, so neutrons equal mass number minus atomic number.

How can you find a missing atomic value?

If you know any two values, you can subtract to find the third.

What information can you find on a periodic table?

Atomic number, atomic mass, element symbol, and sometimes electron configuration.

How are isotopes similar?

Isotopes have the same number of protons and chemical properties.

How are isotopes different?

Isotopes have different numbers of neutrons and different masses.

How do you determine valence electrons?

Valence electrons can be determined from the group number on the periodic table.

What is the structure of a water molecule?

Water has one oxygen covalently bonded to two hydrogens in a bent shape.

How do water molecules form hydrogen bonds?

The partial positive hydrogen of one molecule is attracted to the partial negative oxygen of another.

What are emergent properties of water?

Cohesion, adhesion, high specific heat, expansion upon freezing, and solvent ability.

Why is water cohesive?

Hydrogen bonds cause water molecules to stick together.

Why is water adhesive?

Water sticks to other polar surfaces due to hydrogen bonding.

Why does water have high specific heat?

Hydrogen bonds absorb heat before breaking, stabilizing temperature.

Why does ice float?

Water expands when frozen, making ice less dense than liquid water.

Why is water a good solvent?

Its polarity allows it to surround and dissolve ionic and polar substances.

What is cohesion?

Cohesion is attraction between molecules of the same substance.

What is adhesion?

Adhesion is attraction between different substances.

What is a solute?

A solute is the substance being dissolved.

What is a solvent?

A solvent is the substance doing the dissolving.

What is a solution?

A solution is a homogeneous mixture of solute and solvent.

What is hydrophobic?

Hydrophobic substances repel water and are nonpolar.

What is hydrophilic?

Hydrophilic substances attract water and are polar or ionic.

What ions form when water dissociates?

Water forms H+ (or H3O+) and OH- ions.

What is the pH scale based on?

The pH scale is based on the concentration of hydrogen ions.

What is an acid?

An acid increases hydrogen ion concentration.

What is a base?

A base decreases hydrogen ion concentration or increases OH-.

What does a change in pH mean?

Each pH unit represents a tenfold change in hydrogen ion concentration.

What happens if pH changes by two units?

A two-unit change means a 100 times difference in hydrogen ion concentration.

What happens if pH changes by three units?

A three-unit change means a 1000 times difference in hydrogen ion concentration.

What is a buffer?

A buffer resists changes in pH by accepting or donating hydrogen ions.

Why are buffers important?

Buffers help maintain stable pH for proper biological function.