Biol 1210

Hydrophobic

"water-fearing" - Not readily interacting with water. Hydrophobic compounds are typically nonpolar molecules.

Hydrophilic

"water-loving" - Interacting readily with water. Hydrophilic compounds are typically polar compounds containing partially or fully charged atoms.

Hydrogen Ion

(H+) a single proton with a charge of 1+

Hydroxide Ion

(OH-) ion

Entropy

A quantitative measure of the amount of disorder of any system, such as a group of molecules.

Space filling models

A representation of a molecule where atoms are shown as balls that are color-coded and scaled to indicate the atom's identity and volume. Depicts spatial relationships between atoms more accurately than a ball-and-stick model.

Ball and stick model

A representation of a molecule where atoms are shown as balls—colored and scaled to indicate the atom's identity—and covalent bonds are shown as rods or sticks connecting the balls in the correct geometry.

Functional Group

A small group of atoms bonded together in a precise configuration and exhibiting particular chemical properties that it imparts to any organic molecule in which it occurs.

The theory that simple chemical compounds in the early atmosphere and ocean combined via chemical reactions to form larger, more complex substances, eventually leading to the origin of life and the start of biological evolution.

A substance consisting of atoms with a specific number of protons. Elements preserve their identity in chemical reactions

Molecule

A substance made up of two or more atoms held together by covalent bonds

Structural formula

A two-dimensional representation of molecules that not only shows the number and type of atoms, but also how the atoms are bonded together.

Covalent Bond

A type of chemical bond in which two atoms share one or more pairs of electrons

Dalton (Da)

A unit of mass approximately equal to the mass of one proton or one neutron.

Radioactive isotope

A version of an element that has an unstable nucleus, which will release radiation energy as it decays to a more stable form. Decay often results in the radioisotope becoming a different element.

Why does water have a high specific heat?

A water molecule can make 4 hydrogen bonds.

Which model most accurately represents the current view of the structure of the atom? A. Probability model B. Planetary model

Probability model - we cannot determine the exact motion of electrons. We can only compute the regions where electrons occur most of the time. To emphasize the uncertainty, a diagram showing random motion is more suitable than planetary paths

What is a product?

Any of the final materials formed in a chemical reaction

What is a reactant?

Any of the starting materials in a chemical reaction

Chemical reaction

Any process in which substances combine or are broken down into other substances; involves the making and/or breaking of chemical bonds

Compounds

Any substance that consists of more than one element chemically bonded together

Catalyst

Any substance that increases with the rate of a chemical reaction without itself undergoing any permanent chemical change

Solute

Any substance that is dissolved in a liquid

In a neutral solution the concentration of _____ is _____ to the concentration of _____

In a neutral solution the concentration of hydrogen ions is equal to the concentration of hydroxide ions

Aqueous

In a watery or in a water-based environment. Often used in describing a solution where water serves as the solvent

In molecules, C, H, O, and N usually make ___, ___, ___, and ___ bonds respectively

In molecules, C, H, O, and N usually make 4, 1, 2, and 3 bonds respectively

In salt, what is the nature of the bond between sodium and chlorine?

Ionic

What happens to the concentration of protons in black coffee when you add milk?

It decreases - Milk is more basic than black coffee

How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base?

It's the same reaction running backward or forward - The buffer accepts H+ in one case; it gives off H+ in the other case

Buffers are compounds that _____ .

Minimize changes in pH - Buffers reduce the impact of adding acids and bases on the overall pH of a solution

A(n) _____ refers to two or more atoms held together by covalent bonds

Molecule

What factors are important in making it possible to cool yourself by sweating?

Molecules collide with varied angles and speeds and hydrogen bonds are relatively weak - random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.

Why are covalent bonds between hydrogen and nitrogen or oxygen polar?

Nitrogen and oxygen are more electronegative than hydrogen so electrons are shared unequally

Bonds between two atoms that are equally electronegative are _____.

Nonpolar covalent bonds

A covalent bond is likely to be polar when _____

One of the atoms sharing electrons is much more electronegative than the other atom

A covalent chemical bond is one in which _____

Outer-shell electrons of two atoms are shared so as to satisfactorily fill their respective orbitals

Rank carbon, nitrogen, oxygen and hydrogen in terms of decreasing electronegativity (highest electronegativity first)

Oxygen, nitrogen, carbon, hydrogen

Why doesn't oil mix with water?

Polar molecules attract one another - water molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.

What type of energy is stored in the chemical bonds of a molecule?

Potential energy - potential energy is energy based on position. Chemical bonds will vary in the amount of chemical potential energy they have based on the location of their electrons

Energy

The capacity to do work or to supply heat. May be stored (potential energy) or available in the form of motion (kinetic energy)

Surface tension

The cohesive force that causes molecules at the surface of a liquid to stick together, thereby resisting deformation of the liquid's surface and minimizing its surface area.

Orbitals

The region of space around an atomic nucleus in which an electron is present most of the time. Orbitals are grouped into electron shells.

Hydrophobic interactions

Very weak interactions between nonpolar molecules, or nonpolar regions of the same molecule, when exposed to an aqueous solvent. The surrounding water molecules support these interactions by interacting with one another and encapsulating the nonpolar molecules.

Why is ice less dense than water?

Water molecules make hydrogen bonds at a definite angles and cold molecules move less than water molecules - the ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings

Buffers work best when ...

about half of the buffer molecules are dissociated - this results in the least change in pH when either acid or base is added

Valence electrons

an electron in the outermost electron shell, the valence shell, of an atom. Valence electrons tend to be involved in chemical bonding - the valence shell has higher energy than other occupied shells

Atoms wit the same number of protons but with different electrical charges ______

are different ions

Which of the following is the most spontaneous reaction? A reaction that is _____ a. slightly exothermic and leads to a slight increase in entropy b. slightly exothermic and leads to a huge increase in entropy c. slightly endothermic and leads to a huge decrease in entropy d. highly exothermic and leads to a huge decrease in entropy

b. slightly exothermic and leads to a huge increase in entropy

A solution contains 0.0000001 moles of hydroxyl ions (OH) per liter. What type of solution is this?

neutral

An unequal sharing of electrons within a water molecule makes the water molecule _____

polar

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by _____

polar covalent bonds

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?

polar groups attract one another - Polar molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.

The Prebiotic Soup Model

proposes that certain molecules were synthesized from gases in the atmosphere or arrived via meteorites. Afterwords they would have condensed with rain accumulated in oceans. This process would result in an "organic soup" that allowed for continued construction of larger, even more complex molecules

Rotation can occur around _____

single bonds - rotation allows groups of atoms to change position while preserving the usual bond angles around each atom

The surface metabolism model

suggests that dissolved gases came in contact with minerals lining the walls of deep-sea vents and formed more complex, organic molecules

Cation

A positively charged ion

Polar

1. Asymmetrical or unidirectional 2. Carrying a partial positive charge on one side of a molecule and a partial negative charge on the other. Polar molecules are generally hydrophilic

A solution with a pH of 5 has how many more protons in it than a solution with a pH of 7?

100 times

The innermost electron shell of an atom can hold up to _____ electrons.

2

To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add ...

2 electrons - the neutral atom has 8 electrons. 2 electrons fill the first shell, and 6 go into the second (valence) shell. Two more electrons would fill the valence shell

What is the atomic number of an atom that has 6 protons and 6 electrons?

6

Ion

A charged atom or molecule

Ionic bond

A chemical bond that is formed when an electron is completely transferred from one atom to another. Resulting ions remain associated because of their opposite electrical charges

Nonpolar covalent bond

A covalent bond in which electrons are equally shared between two atoms of the same or similar electronegativity

Polar covalent bond

A covalent bond in which electrons are shared unequally between atoms differing in electronegativity, resulting in the more electronegative atom having a partial negative charge and the other atom having a partial positive charge

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). Thus, H2CO3 ↔ HCO3- + H+ If the pH of the blood drops, one would expect

A decrease in the concentration of H2CO3 and an increase in the concentration of HCO3-

Photons

A discrete packet of light energy; a particle of light

Chemical equilibrium

A dynamic but stable state of a reversible chemical reaction in which the forward reaction and reverse reactions proceed at the same rate, so that the concentrations of the reactants and products remain constant

Electron Shells

A group of electron orbitals with similar energies. Electron shells are arranged in roughly concentric layers around the nucleus of an atom, and electrons in outer shells have more energy that those in inner shells. Electrons in the outermost shell, the valence shell, often are involved in chemical bonding

Organic Compounds

A group of molecules that include at least one carbon atom; most have carbon-hydrogen bonds and carbon-carbon bonds. Organic compounds are widely used by living organisms

The partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called?

A hydrogen bond

What name is given to the bond between water molecules?

A hydrogen bond - A hydrogen atom with a net positive charge is attracted to an oxygen atom with a net positive charge

Solution

A liquid containing one or more dissolved solids or gases in a homogeneous mixture.

Electronegativity

A measure of how strongly an atom pulls shared electrons toward itself in a chemical bond

pH

A measure of the concentration of protons in a solution and thus how acidic or basic the solution is. defined as the negative of the base 10 log of the proton concentration pH = -log([H+])

Temperature

A measurement of thermal energy present in an object or substance, reflecting how much the constituent matter is moving.

Anion

A negatively charged ion

Molecular formula

A notion that indicates only the numbers and types of atoms in a molecule, such as H2O for the water molecule

Which of these relationships is true of an uncharged atom? A. The number of protons is equal to the number of neutrons B. The number of electrons is equal to the number of neutrons C. The atomic mass is equal to the atomic number D. The number of neutrons is equal to the number of protons E. the atomic mass is equal to the number of electrons

A) The number of protons is equal to the number of electrons

A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH?

A- reacts with H+ and become HA

Solvent

Any liquid in which one or more solids or gases can dissolve

A substance that gives up a proton during a chemical reaction, raising the hydrogen ion concentration of water, is most appropriately called _____

An acid - An acid will donate a proton, raising the hydrogen ion concentration and lowering the pH

Radioactive decay is likely to occur when ...

An atom has too many neutrons - the atomic nucleus becomes unstable if the ration of protons to neutrons is too far from unity

Chemical Bond

An attractive force binding two atoms together. Covalent bonds, ionic bonds, and hydrogen bonds are types of chemical bonds.

Valence electron

An electron in the outermost electron shell, the valence shell, of an atom. Valence electrons tend to be involved in chemical bonding

Isotope

Atoms of the same element that have different atomic weights due to the different number of neutrons in the nucleus

Which statement is true of atoms? A. Most of an atom's volume is filled with matter B. Electrons determine the atom's size. C. Protons attract other protons D. Protons repel electrons E. All of the above

B) Electrons determine the atom's shape - probably important to note that all the other options are false and the exact opposite of each statement is true: most of an atom's volume is empty space, protons repel other protons, and protons attract electrons

Which four elements make up approximately 96% of living matter?

Carbon, Hydrogen, Nitrogen, Oxygen

Atomic mass

The average mass of all the isotopes of an element - the atomic mass of a single atom is the number of protons plus the number of neutrons

Why is each element unique with respect to its chemical properties?

Each element has a distinctive number of protons

Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?

Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge

Each water molecule is joined to _____ other water molecules by ____ bonds.

Each water molecule is joined to four other water molecules by hydrogen bonds

Potential energy

Energy stored in matter as a result of its position of the position of electrons that form chemical bonds between atoms

Carbonyl Functional Group

Family: Aldehydes, Ketones Properties: Aledhydes, especially, react with certain compounds to produce larger molecules EX) Acetaldehyde (Aldehydes) EX2) Acetone (Ketones)

Amino Functional Group

Family: Amines Properties: Acts as a base, tends to attract a proton EX) Glycine (an amino acid)

Carboxyl Functional Group

Family: Carboxylic Acids Properties: Acts as an acid, tends to lose a proton in solution EX)

Covalent bonds hold atoms together because they ...

Fill shells without giving atoms too much charge and bring electrons closer to protons

What property of liquid water explains its unusually high heat of vaporization?

Hydrogen bonding - A large amount of energy is required to break the hydrogen bonds in liquid water and change the molecules from the liquid to gas phase

What type of bond must be broken for water to vaporize?

Hydrogen bonds

Atoms of a specific element always have a constant number of _____.

Protons

Endothermic

Referring to a chemical reaction that absorbs heat

Exothermic

Referring to a chemical reaction that releases heat

Why can come insects walk on the surface of water?

Surface tension

Mole

The amount of substance that contains 6.022 x 10^23 of its elemental entities (e.g. atoms, ions, or molecules). This number of molecules will have a mass equal to its molecular weight expressed in grams.

Homeostasis

The array of relatively stable chemical and physical conditions in an organism's cells, tissues, and organs. May be achieved by passively matching the conditions of a stable external environment (conformational homeostasis) or by active physiological processes (regulatory homeostasis) triggered by variations in the external or internal environment

The partial negative charge in a molecule of water occurs because _____

The electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus

Why are hydrocarbons insoluble in water?

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

What determines the type of chemical reactions that an atom participates in?

The number of electrons in the outermost electron shell - An atom is least likely to participate in a reaction when its outermost shell is stable

Molarity

The number of moles of a solute present in 1 liter of solution

Atomic Number

The number of protons in the nucleus of an atom

Knowing the atomic mass of an element allows inferences about what?

The number of protons plus neutrons in the element

Valence

The number of unpaired electrons in the outermost electron shell of an atom; when an atom is involved in covalent bonding, valence often determined how many covalent bonds the atom can form

Chemical energy

The potential energy stored in chemical bonds between atoms

Second Law of Thermodynamics

The principle of physics that the entropy of the universe or any closed system always increases

Why are some reactions exothermic?

The products have lower potential energy than the reactants.

Why do chemical reaction tend to speed up when the concentration of the reactants is increased?

The reactants collide more often

Adhesion

The tendency of certain dissimilar molecules to cling together due to attractive forces.

The Theory of Chemical Evolution

The theory that simple chemical compounds in the early atmosphere and ocean combined via chemical reactions to form larger, more complex substances, eventually leading to the origin of life and the start of biological evolution.

Thermal energy

The total kinetic energy for a system that includes the motion of matter and is measured as temperature

Heat

Thermal energy that is transferred from an object at higher temperature to one at lower temperature

Partial charges occur when ...

a covalent bond links atoms of two kinds and atoms share electrons unequally - Each kind of atom has a different attraction for electrons. Thus, atoms of different kinds share electrons unequally. That gives one atom a partial negative charge; the other atom a partial positive charge

Dissolving is best described as ...

a mingling of molecules and/or ions

Free radical

a substance containing one or more atoms with at least one unpaired valence electron, which makes it unstable and highly reactive

Which answer helps to explain why all living cells need pH buffers? a. Amino acid side chains have many carboxyl and amino groups b. Hydrogen bonds only form at medium pH values c. Nucleic acids must have positive charges to form double helices d. ATP will not deliver energy if it is ionized

a. Amino acid side chains have many carboxyl and amino groups - when these side chains ionize, they exert forces that affect the protein's folding. Thus, if pH isn't stabilized, the proteins will change their folding and may not function properly.

Which statement best explains the physical basis for why nonpolar molecules like oil do not mix with water? a. Nonpolar molecules like oil cannot interact with water molecules via hydrogen bonding b. Nonpolar molecules like oil are positively charged molecules that are repelled by the partial positive charges on water molecules c. Nonpolar molecules like oil hydrogen bond more strongly with other oil molecules than with water molecules d. Nonpolar molecules like oil are negatively charged and are repelled by the partial negative charges on water molecules

a. Nonpolar molecules like oil cannot interact with water molecules via hydrogen bonding - because nonpolar molecules are neither polar nor charged, they cannot interact with the partial charges on water molecules

Which answer helps to explain why carbon atoms tend to make 4 covalent bonds? a. The carbon nucleus has 4 protons b. The valence shell needs 8 electrons c. The first electron shell has 4 orbitals d. All of the above e. None of the above; carbon makes 3 covalent bonds

b. The valence shell needs 8 electrons

By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom's charge stay close to zero? a. The atom has 8 electrons b. The valence shell has 6 electrons c. Shared electrons aren't always near oxygen d. The atom lost electrons from other shells e. The charge isn't near zero; it's -2

c. Shared electrons aren't always near oxygen. - Oxygen keeps 6 electrons to itself. The 4 shared electrons migrate between O and other atoms, thus contributing 4 half charges to oxygen. This gives oxygen about 8 units of negative charge, balancing the atom's 8 protons

Which statement is true of pH buffers? a. They consist of strong acids and strong bases b. They keep the pH of the blood constant c. They consist of weak acids and weak bases d. both a. and b. e. both b. and c.

c. They consist of weak acids and weak bases - By using weak acids and bases, the buffer can absorb or give off H+, stabilizing the pH

Which statement is true of water's tensile strength? a. It results from hydrogen bonding b. It helps to pull water through plants. c. It involves both cohesion and adhesion d. both a. and b. e. a. , b. , and c.

e. a, b, and c. - because of hydrogen bonding, water coheres to itself and adheres to cell walls. That makes it possible to pull water through plants without breaking the water column.

The tendency of an atom to pull electrons toward itself is referred to as its _____

electronegativity

In a double covalent bond, a carbon atom shares ...

electrons in two orbitals

The first law of thermodynamics states that _____

energy is conserved -it is neither created nor destroyed - only transferred and transformed.

To make a buffer, you need to ...

have a weak acid or a weak base half ionized in water - when half of the molecules are ionized, there are plenty of molecules that can either absorb H+ or give off H+ when the pH is disturbed from outside.

Amphipathic

having both a hydrophilic region and a hydrophobic region

Water is a source of _____ for chemical reactions in cells

hydrogen atoms and oxygen atoms

Water has a high specific heat because of the ______

hydrogen bond formed between the hydrogen of one water molecule and the oxygen of another water molecule

Water has surface tension because ...

hydrogen bonds between surface water molecules resist being stretched - the hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated

Though you add heat, the temperature of boiling water remains constant because ...

it takes energy to break hydrogen bonds - at boiling, all the added what is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature

Cohesion

the tendency of certain like molecules (e.g. water molecules) to cling together due to attractive forces.