AKS 3 Overivew Lesson

Law of Conservation of Mass

During chemical reactions, matter is neither created nor destroyed. It is only transformed from one form to another. Mass ALWAYS remains the same.

During a chemical change or a chemical reaction....

• The atoms and molecules that interact with each other are called reactants.

• The atoms and molecules that are produced are called products.

• In a chemical reaction, the bonds are broken and the atoms and molecules are rearranged.

• No new atoms are created. No atoms are destroyed.

• They are simply rearranged.

Chemical Reactions

A chemical equation is a combination of chemical symbols and formulas that explain what happened during a chemical reaction.

Parts of a chemical reaction

Reactants - these are the elements that are interacting. In this experiment, the reactants would be baking soda and vinegar.

Parts of a chemical reaction

Products - this is what is produced. In this experiment, sodium acetate, water, and carbon dioxide are produced.

Parts of a chemical equation

Reaction arrow - tells that a reaction will take place

Multiple Choice

What are the reactants in the following chemical equation?

• CH₄ and 2O₂

• CO₂ and 2H₂O

Multiple Choice

What are the products in the following chemical equation?

• CH₄ and 2O₂

• CO₂ and 2H₂O

Balancing Chemical Equations

For an equation to be balanced, there needs to be the same number of atoms on both sides of the equation.

Multiple Choice

How many carbon atoms are on both sides of the equation?

• 1

• 2

• 3

Multiple Choice

How many hydrogen atoms are on both sides of the equation?

• 2

• 4

• 1

Multiple Choice

How many oxygen atoms are on both sides of the equation?

• 2

• 4

• 1

Multiple Choice

Is this a balanced equation?

• yes

• no

• huh...

Multiple Choice

A student mixes 125 grams of sugar, 250 grams of water and 5 grams of flavoring. The solution weighs...

• 250 grams

• 380 grams

• 375 grams

• 400 grams

Multiple Choice

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit
• Invisible
• Transformed, changed
• None of the above

Multiple Choice

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

Multiple Choice

What will weigh more when a chemical change is complete?  The reactants before the chemical reaction, or the product after the reaction is complete?

• They both will weigh the same
• The product always weighs more than the reactant
• The reactant will weigh more than the product
• They both will loose mass after the reaction

Match

Match the following

• Reactant

  Element

• Reactant

  Compound

• Product

  Compound

2C2

CH4

CO2

• 2C2

• CH4

• CO2

Drag and Drop

P4O10 had a mass of ​12g , and H3PO4 has a mass of 90g, accroding t the law of conservation of mass what is H2O mass? ​ ​

Placeholder

Drag these tiles and drop them in the correct blank above

78g

102

102g

90g

12g

Multiple Choice

What is the reactant in the following equation?
2NaHCO₃  -> Na₂CO₃  +  CO₂  + H₂O

• NaHCO₃
• Na₂CO₃
• CO₂
• H₂O

Multiple Choice

For the equation:
2H₂ +  O₂ --> 2H₂O
How much H₂O will be produced if we react 4g of H₂ and 32g of O₂?

• 4g
• 32g
• 36g
• 28g

In this example, we want the number of Mg (Magnesium) on the LEFT of the arrow to be the same on the RIGHT of the arrow.

We also want the number of O (Oxygen) to be the same number on both the LEFT and RIGHT of the arrow.

Once we count up the Mg and O on both sides, we can see what needs to change.

We CANNOT TAKE ANYTHING AWAY.

We can ONLY ADD using coefficients.

You'll see this done in the next slide...

Multiple Choice

Is the equation balanced?: 2H₂O + O₂ --> 4MgO + 3Fe

• yes

• no

Multiple Choice

Is the following equation balanced?

Al + O₂ ---> 2Al₂O₃

• YES

• NO

Multiple Choice

The following chemical equation IS NOT balanced. What coefficients would make it balanced?

___Al +___ O₂ ---> 2Al₂O₃

• 3 Al and 2 O

• 2 Al and 3 O

Multiple Choice

Balance this equation:

___H₂ +___ Cl₂ --->___ HCl

• It is balanced.

• H₂ + Cl₂ ---> 2HCl

• 3H₂ + Cl₂ ---> 6HCl

• H₂ + 3Cl₂ ---> 6HCl

Multiple Choice

How many HCl molecules do you need to balance this equation? 
Mg +  __HCl --->  MgCl₂ + H₂

• 1
• 2
• 3
• 4

S C I E N C E | L E S S O N 4 . 1 2 | T YP E S O F C H E M I C A L R E A C T I O N S

8

Types of Chemical Reactions {Chem Rxn}

Synthesis – combining
Decomposition – breaking down
Combustion – burning
Single Replacement – one exchange
Double Replacement – two exchanges

There are 5 types of chemical reactions:

Lets look at each one in more depth.

Simpler materials combine to make a compound

Synthesis

compound broken down into simpler materials

Decomposition

one element that starts out by itself switches with another element in a compound.

Single replacement

two positive and negative ions in two different compounds switch places

Double replacement

S C I E N C E | L E S S O N 4 . 1 2 | T YP E S O F C H E M I C A L R E A C T I O N S

1 4

Practice or Check

Identify the following into types of chemical reactions

Equation

Type of Chem Rxn

Na (s) + Cl2 (g) --> NaCl(s)

Cu(s) + AgNO3 (aq) --> Ag(s) + Cu(NO3)2 (aq)

C3H8(g) + O2 (g) --> CO2 (g) + H2O(g)

CaCO3(s) --> CaO(s) + CO2 (g)

KBr(aq) + AgNO3(aq) --> AgBr (s) + KNO3 (aq)

Match

match the equation to the type of chemical reaction

synthesis

single replacement

combustion

decomposition

double replacement

• synthesis

• single replacement

• combustion

• decomposition

• double replacement

Multiple Choice

Identify the type of chemical reaction

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Combustion

Multiple Choice

What type a reaction is taking place in this picture?

• Synthesis
• Decomposition
• Single Replacement
• Double Replacement

Multiple Choice

Identify the following chemical reaction.

Pb + FeSO₄ ----> PbSO₄ + Fe

• Synthesis (or combination)

• Decomposition

• Single displacement

• Double displacement

Multiple Choice

Identify the type of chemical reaction

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Combustion

Multiple Choice

Identify the type of chemical reaction

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Combustion

Multiple Choice

Identify the type of chemical reaction

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Combustion

Multiple Choice

Identify the type of chemical reaction

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Combustion

Multiple Choice

What is the general reaction scheme for a decomposition reaction?

• A + B --> AB

• AB --> A + B

• A + CD --> C + AD

• AB + CD --> CB + AD

• $$C_xH_y+O_2\ ->\ CO_2+H_2O$$

Multiple Choice

Identify the type of chemical reaction

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Combustion