We've already learned how and why elements combine to form different compounds.

Now it's time to move on to bigger and

better things!

Let's learn about how to describe what happens when elements and compounds interact with one another to form new substances.

Chemical Reactions and Equations

Chemical Reactions!!!

Chemical reactions are part of our daily lives and are constantly occurring around us…– Cooking in the kitchen– Driving a car

BUT check out these more exotic and amazing reactions!

Potassium Chlorate and Gummy Bear

https://www.youtube.com/watch?feature=player_embedded&v=txkRCIPSsjM

Potassium Chlorate is often used in fireworks and explosives.

When it is heated to melting point, any item added to it will cause a rapid disintegration in the form of anexplosion (as we see in the video above).

Sodium Acetate Super Saturation

https://www.youtube.com/watch?feature=player_embedded&v=uy6eKm8IRdI

• Sodium acetate, when heated and cooled, becomes supersaturated in water. • When it comes in contact with another object it re-crystalizes. • This reaction also causes heat, and so this has a

practical use in heat pads. • Sodium acetate is also used as a preservative, and

also gives salt and vinegar chips their distinctive taste.

• It is referred to in foods as E262 or sodium diacetate.

Lesson Objectives:

1. Explain what happens during a chemical reaction

2. Identify the reactants and products in any chemical reaction

3. Use the common symbols (s), (l), (g), (aq), and “” appropriately

Introduction • Chemical reaction: occurs when one or

more chemicals react to become different chemicals.

• Atoms rearrange, bonds are broken, new bonds are formed, and the chemical's identity is actually changed.

• Reactants: the substances that are present at the beginning of a reaction.

• Products: the substances that are present at the end of a reaction

Reactants Products

Chemical EquationsThe best way to represent what happens during a chemical reaction is by using a chemical equation.

We've all seen them, even if it was just in cartoons or reruns of Bill Nye. You know, the good 'ole A + B → C.

Chemical Equations

• Chemical equations represent what happens to atoms and molecules on a microscopic level.

• Unfortunately, we can't watch the atoms rearrange with our own eyes, but we can witness the oftentimes, dramatic results of a chemical reaction. Breaking Bad, anyone?

https://www.youtube.com/watch?v=FWgAvSGE5_U

Steps For Writing Chemical Equations

1. Identify the reactants and the products

2. Place the reactants on the left3. Place the products on the right 4. Place an arrow between them

Reactants ProductsA + B C + D

Word Equations

Chemical names are used to represent the reactants and products

in a chemical reaction.

Ex. An aqueous solution of calcium nitrate is added to an aqueous solution of sodium hydroxide to produce solid calcium hydroxide and an aqueous solution of sodium nitrate.

Skeletal EquationsChemical formulas are used instead of chemical names for reactants and products, and symbols are used to

indicate the phase of each substance.

Ex. When sulfur dioxide is added to oxygen, sulfur trioxide is produced.

Skeletal Equations

Ex 2. Ca(NO3 )2(aq) + 2NaOH(aq) → Ca(OH)2(s) + 2NaNO3(aq)

*These are nearly identical to their word counterparts, but the chemical name is replaced by the chemical symbol.

Common Symbols in Chemical Reactions

Let’s Try it in Reverse!

Look at the skeletal equation for the following reaction and write the word equation:

Cu(s) + AgNO3(aq) → Cu(NO3 )2(aq) + Ag(s)

Let’s Try it in Reverse!

Look at the skeletal equation for the following reaction and write the word equation:

Cu(s) + AgNO3(aq) → Cu(NO3 )2(aq) + Ag(s)

Answer: solid copper reacts with an aqueous solution of silver nitrate to produce a solution of copper(II) nitrate and solid silver

Floating on Sulfur Hexafluoride

https://www.youtube.com/watch?feature=player_embedded&v=1PJTq2xQiQ0

• Sulfur Hexafluoride is a colorless, odorless, non-toxic and non-flammable gas.

• Because it is over 5 times denser than air, it is able to be poured in to open containers and light weight objects can float on it as if it were water.

Example 1

Write the following skeletal equation as a word equation:

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

Example 1

Write the following skeletal equation as a word equation:

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

An aqueous solution of hydrochloric acid reacts with an aqueous solution of sodium hydroxide to produce an aqueous solution of sodium chloride and liquid water.

Example 2

Write the following word equation as a skeletal equation:

Gaseous propane, C3H8, burns in oxygen gas to produce gaseous carbon dioxide and liquid water.

Example 2

Write the following word equation as a skeletal equation:

Gaseous propane, C3H8, burns in oxygen gas to produce gaseous carbon dioxide and liquid water.

C3H8(g) + O2(g) → CO2(g) + H2O(l)

Example 3

Write the following word equation as a skeletal equation:

Hydrogen fluoride gas reacts with an aqueous solution of potassium carbonate to produce an aqueous solution of potassium fluoride, liquid water, and gaseous carbon dioxide.

Example 3

Write the following word equation as a skeletal equation:

Hydrogen fluoride gas reacts with an aqueous solution of potassium carbonate to produce an aqueous solution of potassium fluoride, liquid water, and gaseous carbon dioxide.

HF(g) + K2CO3(aq) → KF(aq) + H2O(l) + CO2(g)

Summary

• A chemical reaction is the process in which one or more substances are changed into one or more new substances.

• Chemical reactions are represented by

chemical equations (skeletal and word).

• Chemical equations have reactants on the left, an arrow that symbolizes “produces”, and the products on the right.

Briggs-Rauscher Reactionhttps://www.youtube.com/watch?feature=player_embedded&v=Ch93AKJm9os

• Aka oscillating chemical reaction. • According to Wikipedia: “the freshly prepared

colorless solution slowly turns an amber color, suddenly changing to a very dark blue. This slowly fades to colorless and the process repeats, about ten times in the most popular formulation, before ending as a dark blue liquid smelling strongly of iodine.”

• The reason this occurs is that the first reaction causes certain chemicals to be released in to the liquid, which then, in turn, spark a second reaction, and the process repeats itself until exhausted.