Biology Chapter 2 Study Guide

What are chemicals?

Chemicals are the substances that make up our bodies, the bodies of other organisms, and the physical environment.

Why is water important for life?

Life's chemistry is tied to water; all living organisms require water, and chemical reactions in the body occur in cells consisting of 70-95% water.

What is matter?

Matter is anything that occupies space and has mass (weight).

What is an element?

An element is a substance that cannot be broken down into other substances.

How many elements are there in nature?

There are 92 elements in nature.

What is a compound?

A compound is a substance consisting of two or more different elements in a fixed ratio.

What is an example of a common compound?

Sodium chloride (table salt) is a common compound of equal parts sodium (Na) and chlorine (Cl).

Which four elements make up about 96% of the weight of most living organisms?

Oxygen, carbon, hydrogen, and nitrogen.

What are trace elements?

Trace elements are essential elements needed in minute quantities to prevent disease.

What role does iron play in the body?

Iron is necessary for the transport of oxygen in the body.

What is the consequence of iodine deficiency?

Iodine deficiency prevents the production of thyroid hormones, resulting in goiter.

What are the three subatomic particles in atoms?

Protons (positively charged), electrons (negatively charged), and neutrons (electrically neutral).

Where are protons and neutrons located in an atom?

Protons and neutrons are packed into the atom's nucleus.

What is an atom's atomic number?

The atomic number is the number of protons in the atom.

What is an atom's mass number?

The mass number is the sum of the number of protons and neutrons in the nucleus.

What are isotopes?

Isotopes are different forms of the same element that have the same number of protons but different numbers of neutrons.

What is a radioactive isotope?

A radioactive isotope is one whose nucleus decays spontaneously, giving off particles and energy.

How can radioactive isotopes be used in medicine?

Radioactive isotopes can act as tracers in metabolic processes and are used in medical diagnosis.

What determines an atom's chemical properties?

The distribution of electrons determines an atom's chemical properties.

What are electron shells?

Electron shells are energy levels where electrons are found around the nucleus of an atom.

What happens when atoms have incomplete outer shells?

Atoms with incomplete outer shells tend to react with other atoms to complete their outer shells.

What is a covalent bond?

A covalent bond is the strongest type of chemical bond where two atoms share one or more outer-shell electrons.

What forms when two or more atoms are held together by covalent bonds?

A molecule is formed when two or more atoms are held together by covalent bonds.

What is the significance of the periodic table?

The periodic table provides information about the distribution of electrons in atoms.

What is the role of electrons in chemical activity?

Electrons are the only subatomic particles directly involved in chemical activity.

How do atoms interact during chemical reactions?

Atoms may share, donate, or receive electrons during chemical reactions, resulting in chemical bonds.

What is the relationship between chemical bonds and molecular stability?

Chemical bonds hold atoms together, resulting in stable molecules.

What is electronegativity?

The attraction for shared electrons in a covalently bonded molecule.

What type of bond is formed when atoms have equal electronegativity?

Nonpolar covalent bond.

What type of bond is formed in water due to differing electronegativities?

Polar covalent bond.

What charge does the oxygen atom have in a water molecule?

Slightly negative charge.

What charge do hydrogen atoms have in a water molecule?

Slightly positive charge.

What is an ionic bond?

An attraction between ions of opposite charge.

What happens to an atom when it loses an electron?

It becomes a positively charged ion.

What happens to an atom when it gains an electron?

It becomes a negatively charged ion.

What is a hydrogen bond?

A weak bond formed between a hydrogen atom and an electronegative atom.

What role do hydrogen bonds play in large molecules?

They help maintain the three-dimensional functional shape of the molecules.

What is cohesion?

The tendency of molecules of the same kind to stick together.

How does cohesion relate to water's surface tension?

Cohesion gives water high surface tension, making it behave as if coated with an invisible film.

What is evaporative cooling?

The process where the surface of a liquid cools as the most energetic molecules evaporate.

Why is ice less dense than liquid water?

Hydrogen bonds in ice are stable and form a crystalline structure that is less densely packed.

What is a solvent?

A liquid that dissolves a substance (solute) to form a solution.

What is an aqueous solution?

A solution in which water is the solvent.

What is the pH scale?

A scale that measures how acidic or basic a solution is, ranging from 0 to 14.

What is an acid?

A compound that releases hydrogen ions (H+) into a solution.

What is a base?

A compound that accepts hydrogen ions (H+) from a solution.

What is a buffer?

A substance that minimizes changes in pH by accepting or donating H+.

What is the significance of photosynthesis in chemical reactions?

It converts carbon dioxide and water into glucose and oxygen using sunlight.

What is the relationship between chemical reactions and matter?

Chemical reactions rearrange matter but do not create or destroy it.

What is the effect of hydrogen bonding on water's temperature regulation?

Water can resist temperature changes better than other liquids due to hydrogen bonding.

What is the role of water in biological systems?

Water acts as a solvent, medium for chemical reactions, and helps regulate temperature.