Vocabulary
Explain the relationship between electrons, neutrons, and protons.
An electron is negatively charged and moves around the nucleus; a neutron has no charge and is part of the nucleus; a proton is positively charged and is part of the nucleus.
The nucleus of an atom is made up of
a. protons and neutrons
b. protons and electrons
c. electrons
d. neutrons
a. protons and neutrons
What is an ion?
An ion is an atom or a molecule with an electric charge.
How can a substance be changed from a solid to a liquid? from a liquid to a gas?
If sufficient energy is added to a solid it will change to a liquid and then to a gas.
What is the most common element in the human body?
a. Carbon
b. Hydrogen
c. Oxygen
d. Calcium
Oxygen is the most common element in the human body, making up almost 63% of the average human, followed by carbon (19.37%), hydrogen (9.31%), and nitrogen (5.14%)
What is the difference between an element and a compound?
An element cannot be broken down chemically into simpler substances with the same properties. A compound is composed of the atoms of two or more elements joined by chemical bonds.
High-energy particles that circle the nucleus of an atom are
a. structural formula of a compound
b. dissociation of the ions in the compound
c. number and arrangement of electrons
d. model of the atom
c. number and arrangement of electrons
How are electrons distributed in a covalent bond?
In a covalent bond, one or more pairs of electrons are shared by two atoms.
A magnesium atom has two electrons in its outermost energy level. A sulfur atom has six electrons in its outermost level. How will the two atoms react to form a bond?
The magnesium atom will give up its two electrons to the sulfur atom. As a result, both atoms will have eight electrons in their outermost energy levels and become stable. This is a redox reaction: Mg lost electrons, sulfur gained electrons.
Unlike most other fish, sharks have no ______?
a. Liver
b. Gills
c. Heart
d. Bones
Unlike most other fish, a shark has no bones! Its skeleton is made of cartilage, a material somewhat softer and more flexible than bone.
Distinguish the differences in composition between an acid and a base.
An acid contains more hydronium ions than hydroxide ions, whereas a base contains more hydroxide ions than hydronium ions.
The way in which elements bond to form compounds depends on the
a. structural formula of the compound
b. dissocitation of the ions in the compound
c. number and arrangement of electrons
d. model of the atom
c. number and arrangement of electrons
In a chemical reaction what does a two-direction arrow mean?
A two-direction arrow indicates that the reaction can proceed either way.
The table shows melting and boiling point at normal pressure for five different elements/compounds.
1. Under normal temperature and pressure, which substances exist as solids? liquids? gases?
solids: aluminum
liquids: mercury, water
gases: argon, chlorine
What illness accounted for 40 percent of U. S. military casualties during World War I?
a. Gangrene
b. Smallpox
c. Syphilis
d. Influenza
The Flu killed 43,000 American servicemen mobilized for World War I, representing nearly 40 percent of U. S. military casualties.
Identify the type of reaction that releases free energy.
An exergonic reaction involves a net release of free energy.
Atoms in a solid are
a. fixed in space and show no movement
b. fixed in space but vibrate in place
c. move rapidly
d. activation energy
b. fixed in space but vibrate in place
Many reactions in the cell are exergonic. Why do cells need a continuous supply of energy?
Most reactions require an activation energy to get started.
The table shows melting and boiling point at normal pressure for five different elements/compounds.
2. Which one of the substances are you least likely to encounter as a gas?
Aluminum
Which of the following has the longest recorded life span?
a. Termite
b. Chimpanzee
c. Indian Elephant
d. Oyster
Of these animals, the Freshwater Oyster has the longest recorded life span at 80 years. The longest recorded life span for a termite is 50 years; for a chimpanzee, 50 years; and for an Indian elephant, 70 years.
How are the processes of oxidation and reduction related?
Oxidation involves the giving up of an electron; in reduction, an electron is gained. They are complementary processes.
In a reduction reaction, an atom gains a(n)
a. proton
b. neutron
c. electron
d. nucleus
c. electron
An oxygen atom has six electrons in its outermost energy level. Explain why two oxygen atoms must share four electrons when they form a covalent bond.
Each oxygen atom requires two additional electrons to achieve stability. Thus, two oxygen atoms must share four electrons or two pairs in order for each to have eight electrons and become stable.
Hydrogen gas exists as H2 rather than H. Why?
A hydrogen atom tends to covalently bond to another hydrogen atom, sharing electrons and becoming stable.
What living animal has the heaviest brain?
a. African Bush Elephant
b. Black Rhinoceros
c. Sperm Whale
d. Human
Sperm Whales have the heaviest brain of any living animal. The average Sperm Whale's brain weighs more than 20 pounds (9 kilograms) which is about 4 times heavier than the average human brain.