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?