Concept 2.1

• Matter is anything that takes up space and has mass

• An element is a substance that cannot be broken down into other substances by chemical reactions

• A compound is a substance consisting of two or more different elements combined in a fixed ratio

• Essential elements are natural elements that an organism needs to live a healthy life and reproduce

• Trace elements are required by an organism in only minute quantities

Subatomic Particles

• The three main parts of an atom are

  • neutrons

  • protons

  • electrons

• The unit of measurement for atoms and subatomic particles is a dalton

• Different atomic forms of the same element are called isotopes

• A radioactive isotope is one in which the nucleus decays spontaneously giving particles and energy

• Potential energy is the energy that matter possesses because of its location or structure

Electrons Distribution and Chemical Properties

• electrons are found in different electron shells

• The chemical behaviour of an atom depends mostly on the number of electrons in its outermost shell

  • These electrons are called valence electrons and are found in the valence shell

The formation and function of molecules depend on chemical bonding between atoms

• Attractions between atoms are called chemical bonds

• A covalent bond is the sharing of a pair of valence electrons by two atoms

• Two or more atoms held together by covalent bond constitute a molecule

• 

• 

• The attraction of a particular atom for the electrons of a covalent bond is called its electronegativity

• A nonpolar covalent bond is when electrons are shared equally because two atoms have the same electronegativity

• A polar covalent bond is when an atom is bonded to a more electronegative atom, the electrons will therefore not share equally

Ionic Bonds

• Two resulting oppositely charged are called ions

• Positively charged results in a cation

• Negatively charged results in an anion

• A hydrogen bond is formed when there is a noncovalent attraction between hydrogen and an electronegative atom

• Van Der Waals interactions occur when atoms get just close enough that a few electrons in their valence shell (electron cloud) touch

Chemical reactions make and break chemical bonds

• The making and breaking of chemical bonds leading to changes in the composition of matter are called chemical reactions

• 

• The point at which the reactions offset one another exactly is called chemical equilibrium

• The unequal sharing of electrons and water’s V-like shape make it a polar molecule.

• The phenomenon of the cohesion of water molecules is due to hydrogen bonds

• Adhesion is the clinging of one substance to another

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

• Anything that moves has kinetic energy

• The specific heat of a substance is defined as the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1C

• The heat of vaporization is the quantity of heat a liquid must absorb for 1g of it to be converted from the liquid to the gaseous state

• Evaporative cooling occurs because the hottest molecules, (those with the greatest kinetic energy) are the ones most likely to leave as a gas

Water: The Solvent of Life

• A solution is a liquid that is a completely homogeneous mixture of two or more substances

• A solvent is the dissolving agent of a solution

• The solute is the dissolving agent of a solution

• An aqueous solution is one in which the solute is dissolved in water, water is the solvent

• A hydration shell is formed when there’s a sphere of water molecules around each dissolved ion

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

• Substances that are nonionic and nonpolar are hydrophobic

• Molarity is the number of moles of solute per liter of solution

• 

• An acid is a substance that increases the hydrogen ion concentration of a solution

• A substance that reduces the hydrogen ion concentration of a solution is called a base

Properties of water:

• Anomalous expansion of water

• High specific heat capacity (evaporative cooling and heat of vaporization)

• Hydrogen bonds (pattern when it freezes)

  

• Its versatility of it as a solvent because of the polar molecules

• Cohesion (surface tension)