chapter 2: The Chemical Foundation of Life

A practical set of flashcards covering the key concepts from Chapter 2: The Chemical Foundation of Life.

What is matter?

Anything that occupies space and has mass.

What is an element?

A substance that cannot be broken down into simpler substances by chemical means.

How many elements occur naturally in nature?

92 elements.

What is a compound?

Two or more different elements in a fixed ratio; more common than pure elements.

What is an example of a compound and its components?

Sodium chloride (table salt) is a compound made of sodium (Na) and chlorine (Cl) in a fixed ratio.

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

Oxygen, carbon, hydrogen, and nitrogen.

What are trace elements?

Elements required in minute quantities; examples include B, Cr, Co, Cu, F, I, Fe, Mn, Mo, Se, Si, Sn, V, Zn.

What is the approximate percentage of oxygen in the human body by weight?

About 65%.

What is the approximate percentage of carbon in the human body by weight?

About 18.5%.

What is the approximate percentage of hydrogen in the human body by weight?

About 9.5%.

What is the approximate percentage of nitrogen in the human body by weight?

About 3.3%.

Which trace element helps prevent goiter?

Iodine.

Which trace element is added to toothpaste and mouthwash to reduce tooth decay?

Fluoride.

What is an atom?

The smallest unit of matter that retains the properties of an element.

What are the three subatomic particles?

Protons, neutrons, and electrons.

Where are protons and neutrons located in an atom?

In the nucleus; electrons orbit the nucleus.

What is the atomic number?

The number of protons in the nucleus.

What is the mass number?

The sum of protons and neutrons.

What is atomic mass?

Equivalent to the mass number.

What are isotopes?

Atoms with the same number of protons but different numbers of neutrons; radioactive isotopes decay.

How do carbon-12, carbon-13, and carbon-14 differ?

They have the same number of protons (6) but different numbers of neutrons (6, 7, 8).

How can radioactive isotopes be used in medicine?

As tracers in metabolic processes; used in PET imaging.

What is a covalent bond?

A bond formed when two atoms share a pair of electrons.

What is an ionic bond?

An attraction between ions of opposite charge; example: NaCl.

What is a hydrogen bond?

A weak bond between polar molecules, such as water.

What is electronegativity?

The tendency of an atom to attract shared electrons; more electronegative atoms pull harder.

What is the difference between polar and nonpolar covalent bonds?

Polar covalent bonds have unequal sharing of electrons; nonpolar covalent bonds share electrons equally.

What causes water's cohesion?

Hydrogen bonds cause water molecules to stick together.

What causes water's surface tension?

Hydrogen bonds create high surface tension at the air-water interface.

How do hydrogen bonds affect water's temperature regulation?

They absorb heat when broken and release heat when formed, moderating temperature.

What is evaporative cooling?

Cooling of a liquid surface as high-energy molecules evaporate.

Why does ice float on liquid water?

Ice is less dense than liquid water due to the open hydrogen-bonded lattice.

What is a solvent?

The dissolving agent in a solution; water is the solvent in an aqueous solution.

What is a solution?

A uniform mixture of two or more substances.

What is a solute?

The substance dissolved in a solution.

What is the pH scale?

A scale from 0 to 14 describing how acidic or basic a solution is; each unit is a tenfold change in H+ concentration.

What is an acid?

A substance that donates hydrogen ions (H+).

What is a base?

A substance that reduces hydrogen ion concentration or accepts H+.

What is a buffer?

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

What is ocean acidification?

Rising CO2 dissolved in oceans lowers ocean pH, affecting marine life.

How does rising atmospheric CO2 relate to coral reef health?

Increased CO2 lowers pH, which can reduce calcification and harm corals.