Chemistry Of Life Study Guide And Key 1-16

Front 1

Define: matter, mass, and element. How many naturally occurring elements are there? What four elements compose 96% of living matter?

Back 1

Matter is anything that has mass and takes up space.
Mass is the amount/quantity of matter in an object…it is measured in grams (g).
Elements are substances that cannot be chemically broken down to other types of matter. Elements are the basic unit of matter.
Oxygen, hydrogen, carbon, and nitrogen are the four elements that make up 96% of living matter.

Front 2

List the four states of matter and give an example of each state.

Back 2

Gas (gaseous oxygen), liquid (water), solid (ice), plasma (neon, sun)

Front 3

What is the difference between physical and chemical properties? Physical properties of matter are broken into two categories: extensive and intensive. Define and give examples of both categories.

Back 3

Chemical properties describe a substances’ ability to change into another new substance as a result of chemical change (breaking or forming chemical bonds).These changes tend to be permanent. Burning of coal, rusting of metal, denaturing of proteins are examples of chemical changes.
Physical properties can be observed and measured without chemical changes that alter the identity of the matter. Color, boiling point, taste, mass, boiling point, malleability is examples of physical properties. Physical properties are broken into two categories: 1. extensive properties which are quantity related, such as mass, length or volume and 2. Intensive properties which are quantity independent, in other words will not change because of the amount …such as color, boiling point, malleability

Front 4

An element’s properties depend on the structure of its atoms. Describe the structure of an atom and the charges for each subatomic particle. What is an electron cloud? How many electrons are needed to fill up the energy levels? What is a valence number and how do you find it on a periodic table?

Back 4

In the center of the atom is the nucleus which contains the very large positively charged proton and the large neutrally ‘charged’ neutrons. The very small negatively charged electrons circle the nucleus in an area referred to as the electron cloud. Most of the space of an atom is taken up by the electron cloud, while most of its mass is in the nucleus. The first energy level closest to the nucleus is filled first and it holds up to two electrons. Each energy level after that holds up to eight electrons. An energy level has to be filled before adding electrons to the next level. The number of electrons in the outermost energy level represents the valence number. See the notations on the periodic table columns to determine the valence number. Remember, if there are 1-3 valence electrons the atom tends to give up those electrons and “fall” back to its last full energy level…full = stable. But if it has 5 or more valence electrons it tends to gain more electrons from other atoms to fill up and have the stable eight in its outer level

Front 5

Define isotope and radioisotope.

Back 5

An element can have a varying number of neutrons existing naturally. They all behave the same chemically. The most abundantly occurring form is the one used to calculate the mass number along with its number of protons of course. The isotope is symbolically written to show how many neutrons…ex. H-2 or 2H. Some isotopes are unstable and give off radiation. These are radioisotopes and of course have to be handled carefully. Because radiation shows up well on x-rays, radioisotopes are used in medical procedures and in research as tracers. The radioisotope is added to something then that something moves thru the organism and x-ray shows where it goes because it picks up the radioisotope.

Front 6

Define atomic number and atomic mass number. Know how to find them on a periodic table. How is the mass number different from the atomic mass number?

Back 6

The atomic number is the number of protons. It is used because it stays constant…while neutron number can vary (isotopes), and electrons can be gained or lost in chemical reactions. The atomic number is written above the element symbol on the periodic table.
The atomic mass number is the mass of the total atom (neutrons, protons, & electrons). It is found under the element symbol on the periodic table.
The mass number is only the mass of the nucleus (protons and neutrons). Most of the mass of an atom is in the nucleus because the electrons are so small

Front 7

If given the mass number and atomic number how can you determine the number of neutrons?

Back 7

You can subtract the mass number from the atomic mass number to get the number of neutrons. (because the number of electrons=number of protons so the difference would be the number of neutrons).

Front 8

Both molecules and compounds have chemical bonds. What is the difference between a molecule and a compound?

Back 8

A molecule is any substance that is chemically bonded together. It is a larger category than compounds. It includes substances that are bonded together in no particular ratio (like a lot of the same element say H2…so pure form) and it can also include compounds…because they are chemically bonded together. However, a compound, while it is a type of molecule, is more specific…it has to be particular types of atoms in a specific ratio. Water is an example of a compound. There are two hydrogens and one oxygen…specific ratio. But because water is a compound it is also in that broader category of molecules.

Front 9

List and describe four types of chemical bonds.

Back 9

Covalent bonds-sharing of electrons holds atoms together (water is an example)
Ionic bonds-electron magnetic attraction holds oppositely charged ions together (not as strong as covalent bonds) (NaCl..table salt is an example)
Hydrogen bonds-weak bond between the slightly positive hydrogen atom of a polar covalent bond in one molecule and the slightly negative atom of a polar covalent bond in another molecule ( water molecule bonding to other water molecules is an example, DNA strands are held together by H bonds)
Van der Waals interactions-weak attraction between molecules or parts of molecules that have different charges (parts of proteins held together by these bonds)

Front 10

Compare and contrast polar and nonpolar covalent bonds. Give examples of each type of bond.

Back 10

While both types of bonds chemically bond atoms together by the sharing of electrons, in nonpolar covalent bonds the different elements have similar electronegativity (ability to pull electrons to them) so they equally share the electrons. This results in no polarity of the compound. The fatty acid tails in our cell membrane are held together by nonpolar covalent bonds. However, in a polar covalent bond, one of the elements has a stronger electronegativity than the other element. This results in the ‘stronger’ element having the shared electrons closer to it more often…causing a slight negative charge by that element…and a slight positive charge by the other element because it does not have the shared electrons as much. When a molecule has two oppositely charged areas we say it has polarity…like a magnet has poles. A water molecule is an example of a polar covalent bond.

Front 11

Covalent bonds may be single, double, or triple. Draw carbons connected by each of these types of bonds. How many electrons shared in each type of bond?

Back 11

Single bond C-C share two electrons
Double bond C=C share four electrons
Triple bond C=C share six electrons

Front 12

Show water's chemical formula, structural formula and Lewis Dot Diagram

Back 12

Chemical formula H2O
Structural formula H H
O
Lewis Dot Diagram H:O:

Front 13

A chemical reaction either gives off energy or takes in energy. Define exothermic and endothermic reactions. What are most biological reactions?

Back 13

An exothermic reaction gives off energy, usually in the form of heat. An endothermic reaction requires energy, usually in the form of heat, electrical or chemical. Most biological reactions are endothermic reactions requiring energy intake.

Front 14

Mixtures do NOT form chemical bonds…therefore are not molecules or compounds. Each element retains its own chemical identity. List, describe, and give examples of three types of mixtures.

Back 14

Solution- particles are small and stay uniformly dispersed…they do NOT settle out over time… salt & sugars in water would be an example (think hot and really mixed)
Suspension-the particles are large and settle out over time…example would be our blood plasma…the large red and white blood cells settle out over time
Colloid-particles larger than those in solutions, but small enough that they do not settle out over time. Colloids go back and forth from a sol state( liquid) and a gel state (solid)…this contributes to cytoplasmic streaming which allows movement of cell organelles and can even cause amoeboid action in our white blood cells.

Front 15

A solution has a solvent and a solute. What are they? How do you determine the concentration of a solution?

Back 15

The solute is dissolved in the solvent. Water is often the solvent in biological systems. Common solutes include salts & gases. The concentration of the solution is determined by dividing the amount of solvent by the amount of solvent.