Chapter 2 - 4

Matter

Anything that takes up space and has mass

Element

A substance that cannot be broken down to other substances by chemical reactions

Compound

A substances consisting of two or more different elements combined in a fixed ratio

Essential elements

Of the 92 natural elements, about 20%-25% are this. These are needed for an organism to live a healthy life and reproduce

4 main elements needed for living matter

Oxygen, Carbon, Hydrogen, Nitrogen

Atom

Smallest unit of matter that still retains the properties of an element

Subatomic particles

The particles that make up atoms, protons, neutrons, and electrons; there are over 100 types of them.

Atomic nucleus

Protons and neutrons are packed together in this core

Dalton

The unit of measurement for atoms and subatomic particles, it is the same as an amu.

Atomic number

The number of protons that is specific to that element and is written as a subscript to the left of the symbol for the element.

Atomic mass

The exact mass of an element with the electrons

Mass number

Total number of protons and neutrons in the nucleus of an atom

Isotopes

The atoms that have more neutrons than other atoms of the same element and have a greater mass

Radioactive isotope

The nucleus decays spontaneously, giving off particles and energy

Half-life

A '“parent” isotope decays into its “daughter” isotope at a fixed rate, expressed as this, the time it takes for 50% of the parent isotope to decay

Radiometric dating

Scientists measure the ratio of different isotopes and calculate how many half-lives in years have passed since an organism was fossilized or a rock was

Energy

Capacity to cause change, especially by doing work

Potential energy

Energy that matter possesses because of its location/structure

Orbital

Three dimensional space where an electron is found 90% of the time

Chemical bonds

Attractions between atoms

Covalent bond

The sharing of a pair of valence electrons by two atoms.

Electronegativity

The attraction of a particular atom for the electrons of a covalent bond

Nonpolar covalent bond

A bond between two of the same elements because they share the electrons equally

Polar covalent bond

When one atom’s electronegativity is higher than the other’s

Cation

Positively charged ion

Anion

Negatively charged ion

Ionic bond

Cations and anions that attract each other

Hydrogen bond

Noncovalent attraction between a hydrogen and an electronegative atom

Van der Waals Interactions

Individually weak and occur only when atoms and molecules are very close together

Polar covalent bonds

When electrons are unequally shared, like in H₂O where oxygen is more electronegative than hydrogen so the electrons are closer to oxygen

Polar molecule

Overall charge of a molecule is unevenly distributed. In H₂O, the O₂ has a partial negative charge

Cohesion

Hydrogen bonds that hold a substance together

Surface tension

A measure of how difficult it is to stretch or break the surface tension of a liquid

Adhesion

Clinging of one substance to another

Kinetic energy

Anything that moves has this, the energy of motion

Thermal energy

Related to temperature, the total kinetic energy associated with the random movement of atoms or molecules.

Temperature

Represents the average kinetic energy of the molecules in a body of matter

Heat

Thermal energy in transfer from one body of matter to another

Calorie

The amount of heat it takes to raise the temperature of 1 g of water by 1 C

Kilocalorie

Quantity of heat required to raise the temperature of 1 kg of water by 1 C

Specific heat

Defined as the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 C

Heat of vaporization

Quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state.

Evaporative cooling

As liquid evaporates, the surface of the liquid that remains behind cools down (its temperature decreases)

Solution

A liquid that is a completely homogenous mixture of two of more substances is called this

Solvent

The dissolving agent of a solution is this

Solute

Substance that is dissolved is this

Aqueous solution

One in which the solute is dissolved in water, water is the solvent

Hydration shell

The sphere of water molecules around each dissolved ion is called this

Hydrophilic

Any substance that has an affinity for water is said to be this

Hydrophobic

Substances that are nonionic and nonpolar actually repel water

Molarity

The number of moles of solute per liter of solution

Acid

A substance that increases the hydrogen ion concentration of a solution

Base

A substance that reduces the hydrogen ion concentration

Buffer

A substance that minimizes changes in the concentrations of H⁺ and OH^- in a solution

Ocean acidification

When CO₂ dissolves in sea water, it reacts with water to form carbonic acid.