Earth Chemistry

Matter - is anything that has mass and takes up space The amount of matter in an object is called mass All matter has measurable properties which helps identify it

Physical properties Properties that can be observed without changing the composition of the matter Examples: Color, hardness, state of matter, density

Chemical properties Properties that describe how matter reacts to other substances Example: flammable rust bubbles

Matter has 4 Phases/States Solid – particles are packed together and only vibrate Liquid – particles are less packed together than solids and slide past each other Gas – particles are far apart and move quickly Plasma – similar in properties to a gas but can conduct electricity in certain conditions

Elements Are substances that cannot be broken down into simpler substances by chemical means Each element is made of its own atom Are represented by a symbol They are organized into the periodic table

Periodic Table It has a series of boxes that represent each element The parts in each box Atomic Number – at the top Represents the number of protons Symbol – represent the name of the element Atomic mass – at the bottom Represent the total number of protons plus neutrons

Oxygen 8 O Atomic Number Atomic Mass Symbol

Periodic Table Set Up Rows Go across The atomic number increases by one each time you go across Columns (called families or groups) Go down Each group has a name All elements in the same group have the same number of valence electrons so they react similarly As you go down they get larger

Atoms – the smallest unit of an element (made of mostly empty space) Two parts: Nucleus Protons: − Have a positive charge − Mass = ~ 1 amu Neutrons: − No charge − Mass = ~ 1 amu Electron cloud Electron: − Have a negative charge − Mass = 9.1 x − Force of attracted to the protons in the nucleus hold them in place

An elements protons can’t change or it is not the same element But it can change neutrons or electrons Neutral – have equal number of all particles Isotopes – a different number of neutrons Changes the mass Ions – have a different number of electrons If extra – they have a negative charge If fewer – they have a positive charge

Valence electrons – the electrons that are in the outer shell of an atom They determine: The atoms properties What atoms they can bond with The goal is to have the outer shell full (eight electron in outer shell) If the outer shell is full it’s called inert (or inactive) – won’t react

When atoms bond it is chemically Forms a compounds Compounds have properties are different than the elements in it Example: Water

Representing compounds Chemical formulas – a combination of letters and numbers that the makeup of the compound Include: Symbols Subscripts = little numbers to the lower right Tells the number of atoms of that element Coefficient – large number in the front Tells the number of molecules

Example of Chemical Formula C 6 H 12 O 6 4C 6 H 12 O 6

To show how substance react with each other we use a chemical equation Parts of the equation Reactants – on the right side of the arrow (starting materials) Products – on the left side of the arrow (what is made) All equations must have the number of each type of atom on both sides of the equation

Example of Reaction 2 Ag + S Ag 2 S

How are the substance held together? Chemical bonds – forces that hold together atoms in a molecule Bonds can occur if electrons from different atoms are shared or transferred

Name of Bonds Ionic – transfer electrons Covalent – share electrons

Ionic Verses Covalent Bonds

Factors Affecting Reaction Rates Temperature Surface area/Particle size Concentration of solution Pressure Catalysts Inhibitors

Increasing Surface Area