Describing Chemical Reactions

Describing Chemical Reactions

by Kasandra Saiki

​Bell Ringer

​Describe what happened in the Sodium-Chlorine reaction.

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​Describe what happened in the Hydrogen-Oxygen Reaction.

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What caused the blimp explosion?

​Lets do a quick review of...

​Chemical formulas

​Chemical Equations

​Chemical Formulas

​Law of conservation of mass

​and more!

Coefficients

This is the big number in front of a chemical formula. This number tells how many groups of that formula you have.

3 CO₂

The THREE in front of CO₂ is the coefficient.

Subscripts

The small number after the chemical formula. It only belongs to the element that it immediately follows and counts the amount of that element.

3 CO₂

The TWO after the chemical formula is the subscript.

Multiple Choice

Which is the correct formula for:
 three hydrogen (H)
one sulfur (S)
four oxygen (O)

• H₃SO₄
• HSO₄
• H₄S₃O
• H₂O

Multiple Choice

What is the coefficient for this formula? 9NaCl₂

• 9

• 2

• 1

• 11

Multiple Choice

CH₂Cu₈ - How many Copper atoms are in this formula?

• 1

• 2

• 8

• 16

Reactants

In a chemical equation, the reactants are on the left side of the arrow.

In this example

2Mg + O₂ --> 2MgO

• the reactants are 2Mg + O₂

• Reactants are always on the left.

Products

In a chemical equation, the products are on the right side of the arrow.

In this example

2Mg + O₂ --> 2MgO

• the product is 2MgO

• The products are always on the right.

Multiple Choice

$$C_2H_6\ +\ 5O_2\ \rightarrow\ 2CO_2\ +\ 3H_2O_2$$   Given this chemical equation, what are the PRODUCTS?

• $$C_2H_{6\ }and\ 5O_2$$  

• $$2CO_2\ and\ 3H_2O_2$$  

Multiple Choice

$$C_2H_6\ +\ 5O_2\ \rightarrow\ 2CO_2\ +\ 3H_2O_2$$   Given this chemical equation, what are the REACTANTS?

• $$C_2H_{6\ }and\ 5O_2$$  

• $$2CO_2\ and\ 3H_2O_2$$  

Law of Conservation of Mass

Matter cannot be created or destroyed, it only gets rearranged. In a chemical equation, the left side must be equal to the right side. The Reactants are equal to the Products. If the atoms in the reactants and products are not balanced then we must BALANCE THE EQUATION

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​Lets see how this can be done with the example of Methane and Oxygen!

Multiple Choice

In chemical reactions, what does the principle of conservation of mass mean? Why must we balance chemical equations?

• Matter is not created or destroyed.

• The total mass of the reactants is greater than the total mass of the products.

• The total mass of the reactants is less than the total mass of the products.

• Matter is not changed.

Multiple Choice

Which of the following reactions is balanced?

• 2CH₄ + O₂ -> CO₂ + H₂O

• CH₄ + 2O₂ -> CO₂ + H₂O

• CH₄ + 2O₂ -> CO₂ + 2H₂O

• None of the chemical equations are balanced.

​Now lets learn something new!

​Lets learn about

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​-Types of chemical reactions

​-Where chemical reactions take place!

Did you know there are different types of chemical reactions!

​Lets learn about them!

Multiple Choice

Combining substances to form a new substance, like Na+Cl -> NaCl, this reaction was in the bell ringer!

• Displacement

• Synthesis

• Decomposition

• Oxidation

Multiple Choice

Breaking down a substance into simpler substances, in our lab tomorrow we will witness this type of reaction.

• Displacement
• Synthesis
• Decomposition
• Oxidation

Multiple Choice

What type of reaction is the equation H₂+ O₂ → 2H₂O? This one was in the Bell Ringer Video!

• Synthesis Reaction
• Decomposition Reaction
• Single Displacement Reaction
• Double Displacement Reaction

​Where do chemical reactions occur?

​Let's read and find out!

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​What could be an example of a closed system?

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​What about an open system?

​Lets bring it home!

​Lets figure out why the blimp exploded.

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​How did the gases look in their sealed beakers?

​-What type of system was this?

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​What happened when the hydrogen gas when exposed to oxygen?

​-What type of system was the sky in which the blimp exploded!