Chapter 2: Basic Chemistry

Matter

Anything that takes up space and has mass

Element

A substance that cannot be broken down into simpler substances with different properties

Property

Physical of chemical characteristic of a substance

Atom

The smallest particle of an element (element and its atoms have the same name)

Atomic symbol

One or two letters that represent the name of an element

3 Main Subatomic Particles

Protons, neutrons, electrons

Protons

Positively charged subatomic particles

Neutrons

Neutrally charged subatomic particles

Electrons

Negatively charged subatomic particles

Electron Shell

The circle that represents the average location of electrons

Atomic Number

Number of protons in the nucleus

Mass number

The total number of protons and neutrons in the nucleus

Atomic mass

Average mass number for all isotopes of an element

Atom on a periodic table

Isotopes

Atoms of the same element that have different numbers of neutrons

Tracer

A substance added to a biological system to track its behavior, distribution, and processes at the molecular, cellular, or systemic level

Neutral atom

Positive charges are balanced by equal amount of negative charges

Bohr model

Image

Octet rule

If an atom has more than one shell: the outermost shell is most stable when it has 8 electrons

Which element does not follow the octet rule?

Hydrogen and Helium

How many electrons do hydrogen and helium need to be most stable?

Two electrons (duet rule)

Valence shell

Atoms outermost shell, determines whether atom gives up or accepts electrons

Molecule

Two or more elements bonded together, smallest part of a compound that retains its chemical properties

Compound

A molecule containing at least 2 different elements

Formula

Tells you the number of each kind of atom in a molecule (ex. C6H12O6)

Ions

Charged particles

Ionic Bond

Ionic compounds held together by a strong attraction between negatively and positively charged ions

Salts

Solid substances that usually separate and exist as individuals, formed from reaction of an acid and a base

Ionic bond vs ionic compound

Ionic bond is the process of electrons being transferred between two atoms, while ionic compound is the connection between those atoms as a result

Covalent bond

Two atoms have a STRONG connection and share electrons in such a way that each atom has an octet of electrons in the outer shell

Nonpolar covalent bond

The sharing of electrons between two atoms is equal due to low difference in electronegativities

Electronegativity

The ability of an atom to attract and hold electrons toward itself in a chemical bond

Polar covalent bond

Electrons are not shared equally among atoms due to different electronegativities

Hydrogen bond

The weak attraction of a slightly positive hydrogen to a slightly (electro)negative atom near it (like oxygen, nitrogen, or fluorine)

Calorie

A unit that describes the amount of heat energy need to raise the temperature of 1g of water to 1 degree C

Solution

Combination of solutes

Solute

Dissolved substances

Hydrophilic

Molecules that can attract water

Hydrophobic

Nonionized and nonpolar molecules that cannot attract water

Surface tension

Force that holds moist membranes together due to the attraction of water molecules through hydrogen bonds, allowing liquid to resist external force

Hydrogen ions (H+)

One of two ions that results when a water molecule separates, hydrogen ion that has lost is electron, causing it to have a positive charge

Acids

Substances that separate in water, releasing hydrogen ions (H+)

Hydroxide ions (OH-)

One of two ions that results when a water molecule separates, it has gained an electron, has a negative charge

Bases

Substances that either take up hydrogen ions or release hydroxide ions

pH scale

Scale used to measure the acidity or basicity/alkaninity of a solution

Buffer

A mixture of molecules that release or bind H+ in order to keep pH within normal limits, removes or accepts hydrogen ions

Cohesion

Water molecules are attracted to each other

Adhesion

Water molecules stick to other substances

Specific heat

The amount of heat that is needed for the temperature of 1g of a substance to increase by 1 degree celsius

Water has a ___ specific heat capacity

High

Nonpolar covalent bond electronegativity

Difference is less than 0.5

Polar covalent bond electronegativity

Difference is greater than or equal to 0.5, but less than or equal to 2.0

Ionic bond

Difference is greater than 2.0

If a molecule is symmetrical in 3D, it is a ________ ________ ____

Nonpolar covalent bond

Chemical reaction

The process of bond formation

Ionic compounds are _____ substances that usually ______ and exist as _______ ions in water

solid, separate, individual

Lewis dot diagrams

Representations of molecules showing all the gained or lost electrons

Is water a polar or nonpolar molecule?

Polar

Why is water polar?

Oxygen is electronegative and hydrogen is electropositive

What makes hydrogen bonding so special?

It is a very weak attraction between two atoms, allowing for special characteristics

broken, strong

A single hydrogen bond is easily ______ while multiple hydrogen bonds are collectively quite ______

Capillary action

Movement of water up the roots of plants

large, little

Water having hydrogen bonds allows water to absorb _____ amounts of heat with _____ temperature change

Allows organisms to keep their internal temperatures stable

How does water having a high specific heat help organisms maintain homeostasis?

broken

For water to evaporate, hydrogen bonds must be ______, which requires a lot of energy

Evaporative cooling

Sweating and transpiration (plants absorbing water through their roots) are examples of cooling

hydrogen/hydronium (H2O+), hydroxide (OH-)

When water dissociates, it breaks apart into a ______ ion and a ________ ion

less, expands

Ice is _____ dense than liquid water because water ______ when cooled

Hydrogen bonds form a stable crystal lattice structure, so the molecules are farther apart

Why does water expand when frozen?

survives

Ice insulates lakes=life ______ under ice

Potential Energy

A form of energy which can do work

Entropy

Energy released as heat

Buffer system

Two components that work together to resist changes

Most buffers consist of a…

weak acid (which releases H+) and a weak base (which binds H+)

minimize the change in pH

The function of a buffer is not to keep a solution neutral, but to

Most biochemical processes proceed normally only when the pH remains within a fairly narrow range

Why are buffers important to living organisms

Alkalosis

The pH goes above the normal range, leading to low acidity

Acidosis

The pH goes below the normal range, leading to high acidity

Hydroxide ions (OH-)

What does a base release when it is dissolved?