CH 8 CHEMICAL REACTIONS AND EQUATIONS
SECTIONS 1 AND 2
Chemical Change
One or more substances changes into one or more new substances.
Evidence:
Changes in energy:1. 2. 3. 4.
Chemical Change
Evidence
Formation of new substances1. ________ (bubbles in solution, pressure
change in a closed system)2. _________(a cloudy solid that settles out of
solution)3. _________ change
4. _________change
Collision Theory of Reactions Chemicals must come into contact
(________) The contact must be in the correct
orientation (___________________) There must be enough energy for the
reactants to get started (________________)
Chemical equations
Equations are used to describe chemical processes
Equations show physical states of matter (s, l, g) and some reaction conditions.
In words:Solid magnesium and oxygen gas when heated, react to form solid Magnesium Oxide.
Symbols used in chemical equations
Pt
( ) Solid( ) Liquid( ) Gas( ) aqueous
2 arrows means reversible reaction
Reversible… reaction “goes both ways”The products form, and can “un-form”
Most reactions that happen in your cells are reversible reactions
Elemental forms Most elements
come naturally in ‘ones’
Ex. Sodium = NaMagnesium = MgIron = Fe
Exceptions:1. Diatomic Gases
2. Non Gases
Write unbalanced equations for the following:
Aqueous Sodium Hydroxide and hydrogen chloride gas
React to form Water and aqueous Sodium Chloride
Unbalanced means don’t put any coefficients
Write out this reaction using symbols: Solid Lithium reacts with water, forming
lithium hydroxide solution and Hydrogen gas.
In a reaction
Mass is neither created nor destroyed.
Your bag was a closed systemclosed system. No atoms were added or removed. They were rearranged.
Law of Conservation of Mass
Rules for Balancing Equations
1. Count the number and type of each element on the reactants’ side. Do the same for the products’ side.
2. Check to see if there are any elements not in balance.
3. Use coefficients to balance any elements that are not equal.
4. Coefficients affect all parts of the molecule that follows.
__ N2 + __ H2 __ NH3
Coefficients: multiply through the whole
molecule. Must be a whole number Are placed in front of molecules not
between.
Write balanced equations for the following:
Sodium Hydroxide and hydrogen chloride
React to form Water and Sodium Chloride
Balance this reaction: Lithium reacts with water Forming lithium hydroxide and Hydrogen
gas
Write the equation and balance it using coefficients Lithium reacts with oxygen To produce Lithium oxide
Silver Nitride is produced when silver metal reacts with nitrogen from the atmosphere.
Warm Up
How many Oxygen atoms are there in each of the following compounds?
1. NO2 _______
2. 2 NO2 _____
3. 2 Mg(NO3)2 _______
Balance the following Li + H2O LiOH + H2
C6H12O6 + O2 H20 + CO2
Warm Ups
What is the mass of 1.204E24 molecules of Oxygen gas?
How many formula units are there in 50.0g of Magnesium Chloride?
How many atoms are there in the same amount of MgCl2?