Law of Conservation of Mass

Multiple Choice

The number to the lower side of an element is a 

• Subscript
• Superscript
• Coefficient
• Charge

Multiple Choice

What does the number 4 represent in 4NH₃?

• Subscript

• Superscript

• Coefficient

Multiple Choice

What is the left part of a chemical equation called?
2H_{2 +} O₂ --> 2H₂O

• Reactants
• Products 
• Yields 
• Chemical Equation 

Multiple Choice

What is the right part of a chemical equation called...
2H_{2 +} O₂ --> 2H₂O

• Reactants
• Products 
• Yields 
• Chemical Equation 

Multiple Choice

The number in front of a compound or element is a 

• Subscript
• Coefficient
• Superscript
• Charge

Multiple Choice

The coefficient in  3H₂O is

• 6
• 2
• 3
• 5

Multiple Choice

Which are the reactants in the following reaction?
2Mg + O₂ ---> 2MgO 

• Mg and O
• MgO
• Mg and MgO
• O and MgO

Multiple Choice

​If I burn this piece of paper what type of change is taking place

• Physical

• Chemical

​What do you believe happen to the different things that made up the Hindenburg when it was burned ?

​What do you believe happen to the different things that made up the Hindenburg when it was burned ?

​

​Would the mass of remaining Ash from a burnt paper be the same as that of the paper burnt ?

Poll

Do you believe the mass that is not accounted for was destroyed by the fire ?

• yes

• no

​

​

​

​During a chemical reaction matter is neither created or destroyed even though it might appear that way . Matter is changed into another form affecting the mass of the original reactants

Law of Conservation of Mass

by Garfield Baker

​This is called the Law of Conservation of Mass. The Law of Conservation of Mass states that during a chemical Reaction mass is neither created or destroyed

​

​

In a chemical reaction the starting mass of the reactants must be the same as that of the products .

Open Ended

Why is it that mass of the product APPEARS to have being destroyed ?

​

​The reason was that the water vapor and CO₂ escaped in the air . It is not destroyed but just changed the state that it was in .

​

​This happens in an OPENED SYSTEM

​In an OPEN SYSTEM matter can enter or leave increasing or decreasing the mass of the final product . For example when baking soda and vinegar is mixed and the gas escaped that is an OPEN system

​In a CLOSE SYSTEM no matter is able to enter in the reaction as a result the mass is not affected . For example if Vinegar and Baking Soda is mixed together and Covered no matter ( mass) will be added or lost ,because nothing will be able to enter or leave

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

Multiple Choice

What do we call the chemicals that result from a chemical reaction?

• reactants

• products

• subscripts

• coefficients

Multiple Choice

According to the Law of Conservation of Mass, what happens to the wood and oxygen when it is burned?

• The wood disappears.

• It stays the same chemically.

• The atoms in the wood and oxygen rearrange and form smoke and ash.

• Nothing.

Multiple Choice

The Law of Conservation of Mass States

• Energy cannot be created nor destroyed, it can only change form.

• Mass cannot be created nor destroyed, it can only change form.

• Mass can be created or destroyed, it cannot change form.

Multiple Choice

What types of systems are there?

• Mechanical and Electrical Systems
• Inside and Outside Systems
• Open and Closed Systems
• Human and Machine Systems

Multiple Choice

This type of system allows matter to flow freely in and out...

• Closed System
• Open System

Multiple Choice

A boiling pot with a lid on it to keep in the energy is what type of system?

• Closed System
• Open System

Does the equation below that represent a chemical reaction shows the Law of Conservation of mass to be true ?

Balancing Equations

• ​Because we know that the reactants should be the same as that of the products but is not the case in an OPEN system , Chemical Equations must be balanced

• ​Balancing Equation satisfies the LAW of CONSERVATION OF MASS

• ​To do this Coefficient are added before the elements or compounds

• Coefficient are used to multiply the subscript (number of atoms ) of each elements until both sides are equal

​Chose different elements and add keep adding coefficient until both sides are balanced (same). If there is a subscript when a Coefficient is added they will multiply together . Ex. there were 2 O atoms and a Coefficient of 11 was added making it 22

​Make a Table to show how many atoms of each elements are present on either sides

​This Equation is not balanced . There are 7 Carbon (C) atoms on left while there is 1 on the right. There are 16 Hydrogen(H) on the left while 2 are on the right . There are 2 Oxygen on the on the left while 3 on the right

​Is this Equation Balanced ?

​

​ 2 Al₂O₃-------- 4Al + 3O₂

​

​ Reactant Product

​ Al = 4 Al = 4

​ O = 6 O= 6

Multiple Choice

Is the following equation balanced or unbalanced ?

N₂ +3 H₂ --> 2NH₃

• Balanced

• Unbalanced

Multiple Choice

Is the following equation balanced or unbalanced ? 
Al + O₂ --> Al₂O₃

• Balanced
• Unbalanced

Multiple Choice

Which of the following models best demonstrates a balanced chemical equation?

• F

• G

• H

• J

Multiple Choice

Is this equation balanced?

• yes
• no
• Not enough information

Multiple Choice

Is this equation balanced?

• yes
• no
• Not enough information

Multiple Choice

Bob puts 200 grams of ice into a pitcher with 900 grams of water. He gets distracted and comes back later to find that the ice has melted in the water. How many grams of water does Bob now have in the pitcher?

• 200 g
• 700 g
• 1,100 g
  

How to balance a Chemical Equation ?

Balancing Chemical Equation - Google Slides

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​Reactants Product

Al - 2 Al - 1

O - 3 O - 2

Balance this equation

Li + Cl₂ -> LiCl

Balance this Equation

MgCl₂ --> Mg₄+ Cl₂

​Complete 5 balancing equation problems

Multiple Choice

Balance this equation.
_CF₄ + _Br₂ -- _CBr₄ + _F₂

• 2,1,2,1
• 1,2,2,1
• 1,2,1,2
• 2,2,2,2

Multiple Choice

Balance this equation
_N₂ + _H₂ --> _NH₃

• 1,2,3
• 1,3,2
• 1,1,2
• 2,1,1

Multiple Choice

Balance this equation:

MgCl₂ --> Mg₄+ Cl₂

• It's already balanced.

• 4MgCl₂ --> Mg₄+ 4Cl₂

• 4MgCl₂ --> Mg₄+ 5Cl₂

Multiple Choice

Balance this equation:

2Li + Cl₂ -> LiCl

• 2Li + Cl₂ -> 4LiCl2

• 2Li + Cl₂ -> LiCl₂

• 2Li + Cl₂ -> 2LiCl

Multiple Choice

Which chemical equation best represents the Law of Conservation of Mass?

• H + O → H2O

• H2 + O2 → H2O

• 2H2 + O2 → 2H2O

• H2 + O2 → 2H2O2