Set 2 - Chemistry - Bio 100

A fundamental substance that cannot be broken down into other substances by ordinary chemical means is known as a(n) __________.

element

What four chemical elements make up 96% of the human body?

carbon, hydrogen, oxygen and nitrogen (CHON)

Most of the symbols for the chemical elements are self explanatory, and you will only have to know the major ones.

Some, however, are not so easy to remember, especially if their one-letter symbol has already been taken.

List the chemical symbols for the following elements:

Calcium

Phosphorus

Potassium

Sulfur

Sodium

Chlorine

Magnesium

Iron

Iodine

Calcium - Ca

Phosphorus - P

Potassium - K

Sulfur - S

Sodium - Na

Chlorine - Cl

Magnesium - Mg

Iron - Fe

Iodine - I

Your thyroid needs a specific chemical element to make thyroid hormones. What is that element? ______ If you have a deficiency in this element, your thyroid can swell and enlarge. This enlargement is called a _______.

Iodine is needed to make thyroid hormones.

An enlargement of the thyroid is called a goiter.

Each chemical element is made up of only one kind of _______.

atom

If we are calling something an atom, what can we say about its electrical charge?

They are electrically neutral (otherwise, we don't call them atoms... instead, they would be ions).

The building blocks (components) of atoms are __________.

subatomic particles

What are the three types of subatomic particles?

electrons, protons and neutrons

What electrical charge do each of the subatomic particles have?

electrons have a -1 charge

protons have a +1 charge

neutrons do not have a charge (they are neutral)

Which of the subatomic particles are tiny compared to the other two?

electrons are tiny compared to protons and neutrons (which are about the same mass)

Where are each of the subatomic particles located within the atom?

electrons - orbiting the nucleus

protons - in the center (nucleus) of the atom

neutrons - in the center (nucleus) of the atom

The number of protons a specific atom contains is called the _________.

atomic number

Because an atom is electrically neutral, the atomic number also indirectly tells you the number of _________ in an atom.

electrons

The number of protons plus the number of neutrons a specific atom contains is defined as its ___________.

mass number

Oxygen has an atomic number of 8 . How many protons does an atom of oxygen contain? ______ How many electrons does this oxygen atom contain? ______ If the mass number of an oxygen atom is 18, how many neutrons does it contain? ______

8, 8, 10

Atoms of the same element will always have the same atomic number they but can differ in their mass number. Atoms of the same element with different mass numbers are considered ______.

isotopes

Atoms of a particular element that are isotopes will have the same atomic number but different mass numbers. This means they have different numbers of _______.

neutrons

Protium, deuterium, and tritium are all isotopes of the element, hydrogen. Protium has an atomic number of 1. What is the atomic number of deuterium? What is the atomic number of tritium?

The atomic number of ALL forms of hydrogen is 1!!

If the mass number of tritium is 3 and it has 2 neutrons, what is its atomic number?

1

Tritium is an isotope of hydrogen that is unstable. This means that tritium is a __________ isotope.

radioactive (or radioisotope)

Isotopes that are radioactive have ________(lower/higher) energy and are ________ (less/more) stable than isotopes that are not radioactive.

Isotopes that are radioactive have higher energy and are less stable than isotopes that are not radioactive.

Are systems (reactions, subatomic particles, etc.) "happier" when they are at a higher energy or a lower energy?

The lower the energy a system is, the more stable it is, and the "happier" it is.

Radioisotopes are unstable because they have _______ (too much/too little) energy associated with them. This is due to an excess of what type of subatomic particle? _______

Radioisotopes are unstable because they have too much energy associated with them. This is due to an excess of neutrons.

What does a radioisotope want to do with its excess neutrons? When they do this, what is it called?

Radioisotopes want to get rid of excess neutrons because they represent excess energy. When they release (lose) these subatomic particles, it is referred to as radioactive decay, or radioactive emission.

Radioactivity can strip away electrons from molecules it encounters and can break chemical bonds. At very high doses, it can destroy cells, and it can also ________ proteins and ________ DNA.

denature proteins and mutate DNA.

The Chernobyl nuclear power plant disaster occurred in 1986. One of the radioactive isotopes that was released into the atmosphere was iodine. What type of cancer was found in higher incidences in children over the next few decades?

thyroid cancer

What can carbon dating be used for on fossilized bone? Can carbon dating be used on living tissue?

Carbon dating can be used to analyze fossilized bone to determine approximately when the organism with that bone died.

No, it cannot be used to determine the age of living tissue because when you are alive, your carbon-12 to carbon-14 ratio is the same as the rest of the living world. When an organism dies, it is no longer taking in the carbon from the living world, and its ratio of carbon-12 to carbon-14 will change in a manner that is dependent on how long it has been deceased.

What is the purpose of irradiating fruits and vegetables with gamma rays? Is it safe to eat this irradiated food?

Food may be irradiated with gamma rays to preserve it for longer term travel or storage. Any bacteria or microorganisms that might grow on the food will be killed with the irradiation. It is completely safe to eat this irradiated food because the irradiation has occurred prior to you consuming it and you are not exposed to the radiation directly.

Gamma radiation is very strong, and it can kill living cells. Under what conditions would gamma radiation be beneficial to an individual?

If the radiation can be directed to a specific area in the body, and you want to destroy specific cells, it can be beneficial. An example would be radiation to destroy cancer cells.

Another example would be if you have overactive cells that are not necessarily cancerous, like with certain thyroid disorders.

If a doctor wants to diagnose cancer, one of the ways it can be done is by attaching a radioisotope to glucose. Glucose is our main energy source and since cancer cells are highly metabolic (they need a lot of energy to rapidly divide), they will take up a LOT of glucose. Since the glucose given to the patient is radioactive, it will "light up" highly metabolic cells, like cancer cells. The type of diagnostic tool just described is called a _________ scan.

PET

A thyroid scan can be used to see if the thyroid has grown or if thyroid tissue has invaded nearby areas. This type of scan uses what radioisotope, and why?

Radioactive iodine is administered to someone undergoing a thyroid scan because the iodine will enter and stay in only thyroid cells. It will then "light up" these cells, providing a visual means of determining whether the thyroid has grown or gotten smaller, and if thyroid cells have spread to other areas.

A normal thyroid is shaped like a specific insect. What insect does a normal thyroid resemble?

a butterfly!

A substance containing two or more elements chemically bound to each other is known as a ___________.

compound

The elements of a compound exist in __________ (fixed/variable) ratios.

fixed

Chemical bonds form between two atoms due to interaction between the _________ of those atoms.

electrons

If an electron had a choice, it would prefer to be __________ (further away/closer) to the nucleus because this is the _________ (lowest/highest) energy for the electron.

closer, lowest

If we look at a "shell" diagram of an atom, how many electrons can fit into the first shell? ______ How many electrons can fit into the second shell? _____

2, 8

Electrons that are in the outermost shell of an atom are called __________ electrons, and they have the ________ (highest/lowest) energy of all the electrons.

valence, highest

Which electrons are most stable, those in the 1st, 2nd or 3rd shell?

Electrons in the 1st shell are most stable because they are closest to the positive nucleus (and they are attracted to it). These electrons are at the lowest energy compared to other electrons.

Only certain electrons of an atom are able to form chemical bonds with other atoms. Which electrons are these?

Only the valence (outermost shell) electrons are capable of forming chemical bonds.

Only elements that have valence shells that are _________ will participate in chemical bonds. Elements that already have completely filled valence shells are non-reactive, or ________.

unfilled (once a valence shell is filled, then all of the other shells will be filled to capacity, and the atom/ion will be "happy")

Elements that already have completely filled valence shells are non-reactive, or inert. These are called the Noble Gases.

What type of chemical bond forms when one atom gives up an electron to another atom?

ionic bond

When an atom gives up or receives one or more electrons it becomes charged, and we longer call it an atom. What do we call it?

an ion

Lithium has an atomic number of 3. How many electrons does lithium have in its valence shell? _____

Fluorine has an atomic number of 9. How many electrons does fluorine have in its valence shell? _____

Lithium has one electron in its valence shell.

Fluorine has seven electrons in its valence shell.

What kind of bond will form between lithium and fluorine? What happens to lithium and fluorine when this bond occurs?

An ionic bond will form between lithium and fluorine. When this bond occurs , lithium becomes positively charged (+1) and fluorine becomes negatively charged (-1).

Are ionic bonds in the solid form strong or weak? Why?

Ionic bonds in the solid form are very strong because the positively charged ions surround themselves with negatively charged ions and vice versa. These ions are held together very tightly because they are strongly attracted to one another.

Are ionic bonds in water stronger or weaker than ionic bonds in the solid form?

Ionic bonds are rather weak in water, and the ions will come apart. They are very strong, however, in the solid form. An example would be table salt. In the solid form, the ions are held together very strongly, and a crystal of many ions bound to each other is formed. However, when placed in water, the water molecules "bump" the ions apart and dissolve the crystal.

The process by which an electron is transferred is called ___________.

ionization

Ionic bonds between two elements form what type of compound?

salts

When two atoms share a pair of electrons (or more than one pair), they are forming a ______________ bond.

covalent

How many electrons does each atom contribute to a single covalent bond? A double covalent bond?

Each atom contributes, or "donates", one electron to the pair of electrons that make up a single covalent bond. Each atom "donates" two electrons to form two pairs of electrons that make up a double covalent bond.

A measure of how well an atom attracts electrons is known as the atom's _____________.

electronegativity

Atoms that attract electrons well have _____ (lower/higher) electronegativities

higher

The atomic number of sodium is 11 and the atomic number of fluorine is 9. Which has the higher electronegativity, sodium or fluorine?

fluorine

If you look at their electron shells, sodium has a single outer shell electron and fluorine has seven. Sodium and fluorine would form an ionic bond, with fluorine stealing sodium's single outer shell electron. Therefore, fluorine must have a higher electronegativity.

If you look at the four most prevalent elements in the human body, what is the order of their electronegativity from highest to lowest? Which two elements have the closest electronegativities?

The four most prevalent elements (carbon, hydrogen, oxygen and nitrogen) have the following electronegativity rankings: O > N > C > H

Carbon and Hydrogen have rather close electronegativities, so when they form a covalent bond between them, they behave as if they are equal (even though Carbon has a higher electronegativity)

What is meant by the term, polarity with respect to chemical bonding?

The term polar means different, and with respect to chemical bonding, we are talking about different electronegativities (attraction for electrons) between two atoms. When one atom attracts electrons more than another (past a certain threshold), the bond they will form will be polar, and electrons will tend to be drawn closer to the atom with the higher electronegativity. If there isn't any difference between the electronegativities between two atoms (or very little), then electrons between the two atoms will tend to stay equidistant between the two atoms, and the bond they will form is a nonpolar bond.

When two atoms are sharing a pair of electrons equally they are participating in a ____________ covalent bond, and when they are sharing a pair of electrons unequally they are participating in a ___________ covalent bond.

nonpolar, polar

When two identical atoms form a covalent bond, that covalent bond is always ____________ (polar/nonpolar). Why?

When two identical atoms form a covalent bond, that covalent bond is always nonpolar, because two identical atoms have to have the same electronegativities. Therefore, they have an equal attraction for electrons and would share the pair of electrons equally.

Covalent bonds between two different atoms are nearly always ___________ (polar/nonpolar), the exception being between carbon and ___________.

polar, hydrogen

Remember, the only two examples (for our purposes) in which a covalent bond is nonpolar is between two identical atoms, and between carbon and hydrogen. Although carbon and hydrogen have different electronegativities, they are close enough in value so that they share electrons equally (which is a nonpolar covalent bond).

Which of the two bonds, ionic or polar covalent, is more polar? Why?

The ionic bond is more polar. With an ionic bond, the two atoms forming that bond have such different electronegativities, there is an actual transfer of an electron from one to the other, and they become charged (ions). This is the most polar you can get, where they are so different in their attraction for electrons that one steals, and one gives up, an electron.

Polar covalent bonds are polar, but not as polar as ionic bonds because there is still a sharing of a pair of electrons between the two atoms involved; the electronegativities among the two atoms are different enough for one atom to pull the pair of electrons closer to it, but not different enough to pull them completely away from the atom it is forming the bond with.

Hydrogen bonds are very ________ (weak/strong) bonds that are incredibly important in biological molecules. They usually occur between a hydrogen atom and either ___________ or ____________.

Hydrogen bonds are very weak.

They usually occur between a hydrogen atom and either oxygen or nitrogen.

Note: fluorine can also form a hydrogen bond with water but we will only focus on oxygen and nitrogen.

The hydrogen in a hydrogen bond MUST be slightly __________ (positive/negative) and the oxygen or nitrogen MUST be slightly ___________ (positive/negative). In order to be slightly positive or negative, these atoms must ALREADY be participating in __________ covalent bonds.

The hydrogen in a hydrogen bond MUST be slightly positive and the oxygen or nitrogen MUST be slightly negative. In order to be slightly positive or negative, these atoms must ALREADY be participating in polar covalent bonds.

Can a hydrogen bond form between water and methane gas? In other words, between H2O and CH4?

NO!

The hydrogen in the water would be capable of forming hydrogen bonds with other molecules because it is slightly positive due to the polar covalent bond it forms with oxygen. Similarly, the oxygen in water could also form hydrogen bonds with other molecules because it is slightly negative. However, the molecule CH4 is completely nonpolar... all of the bonds between carbon and hydrogen are nonpolar covalent bonds. This means that the carbon atoms and the hydrogen atoms are completely neutral... they do NOT have a slightly negative or positive charge and would not be attracted to either the slightly positive hydrogen OR the slightly negative oxygen in water!

It takes ________ (less/more) heat energy to increase the temperature of water than that of most other fluids. Why is this the case?

It takes more heat energy to increase the temperature of water than that of most other fluids.

This is because in order to increase the temperature, molecules have to move faster. The water molecules are held together by multiple hydrogen bonds, and although they are rather weak, they must be broken before the water molecules will begin to move around and raise the temperature. Breaking the hydrogen bonds requires energy, and some of the heat energy added is used up to break these bonds before they begin to move around. The molecules found in most other fluids are not attached to each other through any bonds, so they are free to immediately move around with added heat energy. The temperature then immediately rises with these other fluids.

The type of bond that forms between the hydrogen and oxygen atoms within a single water molecule is called a _____________ bond, and the type of bond that forms between the hydrogen and oxygen atoms between different water molecules is called a _______________ bond.

polar covalent, hydrogen

Water has a rather ________ (high/low) heat of vaporization, which is the energy required for a water molecule to go from a liquid to a gas.

high

We all associate sweating with cooling ourselves down, but is it the actual sweating that cools us down or something else? What types of bonds in the water (sweat) are being broken when we cool down?

It's actually the evaporation of water in sweat from our bodies that cools us down, NOT the actual sweating. Because water has such a high heat of vaporization, it takes a lot of energy for the multiple hydrogen bonds holding the water molecules to each other to break, which is required for converting the liquid to a gas so it can evaporate from our skin. This energy is then dissipated, and we cool down.

Ice is _______ (more/less) dense than liquid water, which is why ice _________ (sinks/floats) in liquid water.

less, floats

The hydrogen bonds in ice are ___________ (closer together/further apart) than the hydrogen bonds in liquid water.

further apart

The attraction of water to other water molecules is called ______. The attraction of water to other water molecules is called ______.

cohesion, adhesion

Water has a very _______ (low/high) surface tension due to the _______ (cohesive/adhesive) forces among water molecules.

high, cohesive

The openings in leaves that allow for gas exchange are called __________.

stomata

How is water able to move up a plant, against gravity? Plants have evolved vascular tissue called _________ that allow for this water transport.

xylem

Food that is made by the plant leaves through photosynthesis must travel to the rest of the plant and its roots. Vascular tissue that allows for this transport is called _________.

phloem

Water is a very _______ (polar/nonpolar) molecule, and thus dissolves ________ (polar/non-polar) substances well.

polar, polar

Why is water able to dissolve polar molecules but not able to dissolve nonpolar molecules?

Water can form hydrogen bonds with polar molecules, and when it does that, the attraction between these two types of molecules causes the polar molecule to dissolve (in chemistry, the saying is, "like dissolves like"). But nonpolar molecules are not able to form hydrogen bonds with water and thus, they are not attracted to the water.

Molecules are compounds in which the atoms are held together by covalent bonds. We know that water dissolves those molecules which are polar (consist of all, or mostly all, polar covalent bonds) through its ability to form hydrogen bonding with the polar molecule. Water dissolves ionic compounds, like salts, in a different way. How so?

When you have a solid salt, the ions are held very tightly together due to their opposite charges (like Na+ and Cl- ions). But when you put them in water, the water molecules will "bump off" individual ions off the solid salt by forming a solvation "cloud" of water around them. The slightly positive hydrogen atoms of water will surround the negative ion of the salt, and the slightly negative oxygen atom of water will surround the positive ion of the salt. This will only occur, however, if you have enough water to surround the ions. If you dump too much salt in water, some of it will not dissolve because there is not enough water to "bump off" the ions from the solid salt.

Polar substances ______ (do/do not) dissolve in water well. The term for this is ________. Nonpolar substances ______ (do/do not) dissolve in water well. The term for this is ________.

Polar substances do dissolve in water well.

The term for this is hydrophilic.

Nonpolar substances do not dissolve in water well.

The term for this is hydrophobic.

What is pH? It is a measure of the concentration of free ____________ in a solution.

hydrogen ions

If you were to take a snapshot of the water molecules in a bucket of pure water, would you find any free hydrogen ions and hydroxyl ions, or would everything in the bucket be intact water molecules?

You would find a very small percentage of free hydrogen ions and hydroxyl ions, and mostly intact water molecules. But it is the free hydrogen ions that are present that is the basis for our pH measurements, so all of them are important!

When you have pure water, the concentration of free hydrogen ions (H+) is ___________ (greater than/less than/the same as) the free hydroxyl ions (OH-).

the same as

The pH scale runs from ____ to ____, where pH ____ is considered neutral (pure water).

0 to 14, 7

Solutions with a pH less than 7 are considered _______, and solutions with a pH greater than 7 are considered ________.

acidic, basic (or alkaline)

As you decrease the pH, you are ____________ the concentration of hydrogen ions (H+).

increasing

The pH scale is __________, one unit change in pH respresents a _________ change in the concentration of hydrogen ions.

logarithmic, 10-fold

As you go from a pH of 9 to a pH of 6, are you increasing or decreasing the concentration of hydrogen ions? _______ By how much are you changing the concentration of H+?

You are increasing the concentration of hydrogen ions. The pH has changed by 3 units, so this is a 10x10x10 = 1,000-fold change in H+ concentration.

What is the definition of an acid? What is the definition of a base?

An acid is a substance that donates (or releases) free H+ when dissolved in water. A base is a substance that combines with (or accepts) free H+ when dissolved in water.

Does adding an acid to a solution increase or decrease the free hydrogen ion concentration? What about adding a base?

Adding an acid to a solution increases the free hydrogen ion concentration and adding a base to a solution decreases the free hydrogen ion concentration.

Anytime you see H+, you should think of it as being ______.

acid

A substance that will release H+ or combine with H+ to keep the pH from changing is called a ________. This means that when added to a solution, it will make the solution _______ (easier to change the pH/resist changes in pH).

buffer

A buffer will make the solution resist changes in pH.

The normal pH of human blood is between 7.35 and 7.45 (average = 7.4). We have a buffer in our blood that helps maintain this pH. This buffer is similar to what household substance?

baking soda

If you blow CO2 into a solution, you would see __________ (a decrease/an increase/no change) in the H+ concentration of the solution and the pH would ___________ (go down/go up/not change).

You would see an increase in the H+ concentration and the pH would go down.

If the pH of your blood becomes too acidic, what would happen to the CO2 levels in your blood? How would you respiratory system react?

If the pH of your blood becomes too acidic, it means the H+ levels are increasing. This H+ would combine with bicarbonate in your blood to form carbonic acid, which would quickly dissociate into carbon dioxide and water (see equation below). So the CO2 levels in your blood would increase, and your respiratory system would react by making you breathe faster to get rid of this CO2 (and get rid of the acid, bringing the pH of the blood back up).

H+ + HCO3- ----> H2CO3 ----> H2O + CO2