Unit 1- topic 1

Structure of Water and Hydrogen Bonding

Matter

Anything that takes up space and has mass, including rocks, metals, oils, gases, and organisms

Element

A substance that cannot be broken down into other substances by chemical reactions; there are 92 naturally occurring elements

Compound

A substance consisting of two or more different elements combined in a fixed ratio, such as H2O or NaCl

Essential Elements

20-25% of the 92 naturally occurring elements that are essential for survival and reproduction; CHOPN make up 96% of living matter

Trace Elements

Elements required by an organism in very small quantities

Atomic Number

The number of protons in an atom

Atomic Mass

The number of protons plus neutrons averaged over all isotopes

Valence Electrons

Electrons in the outermost shell of an atom that determine its chemical properties

Bohr Model

A model showing electrons orbiting the nucleus of an atom in defined energy levels

Lewis Dot Model

A simplified representation of an atom that shows only the valence electrons

Chemical Bonds

An attraction between two atoms resulting from the sharing or transferring of valence electrons

Electronegativity

A measure of an atom’s ability to attract electrons to itself

Covalent Bonds

Bonds formed when two or more atoms share electrons, typically between nonmetals

Nonpolar Covalent Bond

A bond where electrons are shared equally between two atoms

Polar Covalent Bond

A bond where electrons are not shared equally, resulting in partial charges

Ionic Bonds

The attraction between oppositely charged ions, typically formed between metals and nonmetals

Hydrogen Bonds

An attraction between a partially positive hydrogen atom in one polar covalent molecule and an electronegative atom in another

Polarity

The property of water that results from the unequal sharing of electrons, making it a polar molecule

Cohesion

The attraction of molecules for other molecules of the same kind, responsible for surface tension in water

Adhesion

The clinging of one molecule to a different molecule, allowing water to resist the pull of gravity in plants

Capillary Action

The upward movement of water due to cohesion, adhesion, and surface tension

High Specific Heat

The ability of water to resist changes in temperature due to hydrogen bonds

Evaporative Cooling

The process where water absorbs heat when it evaporates, cooling the surface it leaves

Density of Ice

Water expands and becomes less dense when it solidifies, allowing ice to float and marine life to survive beneath it

Solvent

A substance that dissolves other substances; water is a versatile solvent due to its polar nature

Solution

A homogeneous mixture of two or more substances, consisting of a solvent and a solute

Solute

Substance that is dissolved

Group

elements in the same vertical column have the same number of valence electrons

Period

Elements in the same horizontal row have the same total number of electron shells

Octet Rule

Elements will gain, lose, or share electrongs to complete their valence shell and become stable

Intermolecular bond

Bond that forms between molecules