Chapter 4: The Chemical Bases of Life Study Guide

What is a molecule?

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

A compound that adds H+ ions from a solution

ACID

Hidden Word:

Adhesion

How does a base differ from an acid?

An acid donates H+ ions to an aqueous solution, whereas a base removes H+ ions from it.

What is a difference between an element and a compound?

An element is a pure substance. A compound is made up if two or more elements combined together completely.

Contrast an ionic bond and a covalent bond.

An iconic bond forms when an atom transfers an electron to another atom. A covalent bond forms when two atoms share electrons.

A compound that removes H+ ions from a solution

BASE

A chemical bond that occurs when an atom transfers electrons

IONIC

A different form of an element that has a different number of neutrons

ISOTOPE

What are the four most common elements in living things?

The four most common elements in living things are oxygen, carbon, hydrogen, and nitrogen.

The tendency of molecules of the same kind to stick to one another

COHESION

A substance containing two or more elements that are chemically combined into a fixed ratio

COMPOUND

What properties of water help more it upward from the roots of a plant>

Cohesion and Adhesion helps water move upward from the roots.

What happens during a chemical reaction?

During a chemical reaction, chemical bonds between atoms are broken and reformed, forming new substances.

A pure substance that cannot be broken down into other substances by chemical means

ELEMENT

True or False: A(n) covalent bond is a weak attraction between a hydrogen atom of one molecule and a slightly negative atom of another molecule.

False: Hydrogen bond

True or False: The starting materials for a chemical reaction are products.

False: Reactants

What causes water to be a polar molecule?

Oxygen pulls electrons much more strongly than hydrogen, causing the oxygen atom to be slightly negative and the two hydrogen atoms to be slightly positive.

A molecule in which opposite ends have opposite electric charges

POLAR

Which atom is likely to be more chemically reactive, an atom with a partly filled energy level or an atom with all energy levels completely filled.

The atom with the partly filled energy level is more chemically reactive because it tends to fill in its energy levels with electrons from other atoms. The atom with all the energy levels completely filled does not need more electrons and does not tend to react with other atoms.

Describe the three types of small particles within an atom and explain how they are arranged.

The three types of small particles within an atom are Protons, Electrons, and Neutrons. Protons have a positive electrical charge (+). Electrons have a negative electrical charge (-). Neutrons have no electrical charge. Protons and Neutrons make up the nucleus and electrons move continuously around the outside of the nucleus.

True or False: A(n) aqueous solution is a uniform mixture of water and another substance.

True

True or False: Trace elements make up less than 0.01 percent of your body mass.

True

How do an isotope and a radioactive isotope differ?

Unlike an isotope, radioactive isotope has unstable nucleus which breaks down over time giving off radiation in the form of matter and energy.

This diagram shows a(n) __________________, the smallest possible particle of an element.

an atom

Matter

anything that takes up space and has mass

The number of protons in the atom of an element is known as the element's ___________________.

atomic number

Ion

electrically charged atom or group of atoms

pH scale

range of numbers that is used to describe how acidic or basic a solution is

Buffer

substance that causes a solution to resist changes in pH.

Solvent

substance that dissolves another substance

Solute

substance that is dissolved in a solution

Solution

uniform mixture of two or more substances