Bell Ringer: Tuesday 10/22/13

If mass is conserved it means that the mass is

always the same or does not change. The Law of Conservation of Mass applies to chemical changes. When considering a chemical change this would mean that the total mass of all of the reactants in the chemical reaction is equal to the total mass of products in the chemical reaction.

• What is the main idea of the paragraph?

• What does it mean when mass is conserved?

MYP UNIT QUESTION: HOW CAN SUCH A SMALL THING IMPACT OUR ENVIRONMENT IN SUCH A BIG WAY?

Essential Question: What happens to the matter in substances during a chemical reaction?

Area of interaction: Environment

Learner profile words: Communicator & Thinkers

Standard:

S8P1. Students will examine the scientific view of the nature of matter.

g. Identify and demonstrate the Law of Conservation of Matter.

Learning Target:

Today I am learning that matter is not lost during a chemical equation. This is important so that I can understand that the mass you start with will be the mass you end with .

Homework: Study for the upcoming vocab quiz on Thursday: Law of conservation of matter, reactants, products, subscript, coefficient, open system, closed system..

Agenda

• Opening: – Complete Lego Lab

• Work session: – 1st and 2nd – GPB video on LCM

– 5th & 6th period Short Cornell Notes

• Closing – 1st & 2nd- Exit Ticket

– 5th and 6th Cornell Notes Summary

Opening

• Complete Lego Lab

Work Session • Complete the notes as you review the

video and place on IAN pg.

The Law of

Conservation

of Matter

We’ve talked about changes

in matter…

• The evaporation of a puddle of

water

• Rust forming on a metal fence

HOWEVER…

•No matter is

created or

destroyed by

such changes!

•The total

amount of

matter remains

constant.

The Law of Conservation of Matter

• During a chemical reaction, matter cannot be created or destroyed.

• Even though the matter may change from one form to another, the same number of atoms exists before and

after the change takes place!

Since the overall mass of the

matter does not change…

• The mass of the reactants – the

substances there before the reaction

occurs – must equal the mass of the

product – the substances there after

the reaction takes place.

Mass of

Reactants

Mass of

Products

So……. Chemical equations must be balanced, meaning the numbers and kinds of atoms must be the same on both sides of the reaction arrow

PUT DOWN YOUR NOTES AND CONCENTRATE ON THE NEXT SLIDE

An Example of the L.C.M.

• Test tube containing lead nitrate is placed upright in a flask that contains potassium iodide.

• What are these? – REACTANTS!

• They don’t mix!

• A stopper is put in place to create a closed system – an environment where matter cannot enter or escape.

• The mass of the system is found.

• After the mass is found, the system is turned upside down so the lead nitrate can mix with the potassium iodide.

• They create lead iodide and potassium nitrate.

• Although the matter changed in form, the total mass of the system remains unchanged.

The Formation of Rust

• Iron – Hard, gray-colored

metal

• Rust – Flaky, orange-red

solid

When iron reacts with oxygen

in the air, they form rust or

IRON OXIDE.

• This is written as:

Iron + Oxygen Iron Oxide

Fe Fe

Fe Fe

O2

O2 O2

Fe2O3 Fe2O3

TAKE A

LOOK AT

THE

NUMBERS

How many Iron

molecules?

How many

Oxygen

molecules?

What about

the

PRODUCT?

All Chemical Reactions follow

the Law of Conservation of Matter

• With Iron Oxide, the MASS STAYS THE

SAME!

– The total number of iron atoms and

oxygen atoms in the reactants is the same

as that in the product.

– The atoms were just rearranged!

•No new atoms were created and none were

destroyed!

Ok Time For More Notes!!

When a chemical reaction occurs, it can be described by an equation.

The chemicals can be represented by their names or by their chemical symbols.

Unlike mathematical equations, the two sides are separated by an arrow, that indicates that the reactants form the products and not the

other way round. C + O2 CO2

Carbon + Oxygen Carbon Dioxide

The chemicals that react (called the reactants) on the left-hand

side

The chemicals that they produce (called the products) on the

right-hand side.

How to Read Chemical

Equations.

2Na + Cl2 2NaCl

Reactants –

substances being

used in the reaction

(starting materials on

Left side of equation)

Products – new

substances formed

(ending materials on

Right side of

equation)

How to Read Chemical

Equations.

2Na + Cl2 2NaCl

Coefficients – Whole numbers in

front of compounds. It tells you the

quantity or number of molecules of the

compound.

ex. 2 NaCl = 2 sodium chloride

molecules

How to Read Chemical

Equations.

2Na + Cl2 2NaCl

Subscripts – small numbers following

elements. It tells you the number of

atoms of a particular elements.

*When balancing equations subscripts cannot be

changed.

ex. H2O = 2 -H’s , 1- O

Determining the Mass of Reactants and Products

• REMEMBER: The mass of the reactants is always equal to the mass of the products.

Mass of

Reactants

Mass of

Products

Ex. 2H2SO4 – 2 molecules of Sulfuric Acid

A coefficient is distributed to ALL elements in a

compound

2 – H2 (for a total of 4 H atoms)

2 – S (for a total of 2 S atoms)

2 – O4 (for a total of 8 O atoms)

Balancing is done by placing coefficients in front of

the formulas to insure the same number of atoms

of each element on both sides of the arrow.

Coefficients

1 - List all of the atoms.

2 - Count the number of each type of atom in

the reactant.

3 - Count the number of each type of atom in

the product.

4 - Note which atoms are not balanced.

5 - Select an atom to balance.

5 Steps for Solving

Chemical Equations

Step 1

List out all of the atoms.

Ex.

(NH4)2Cr2O7 Cr203+N2+H2O

1-

2-

3-

4-

Step 2

Count the number of each type of

atom in the reactant.

(NH4)2Cr2O7 Cr203+N2+H2O

1-

2-

3-

4-

Step 3

Count the number of each type of

atom in the product.

(NH4)2Cr2O7 Cr203+N2+H2O

1) 2- Nitrogen

2) 8- Hydrogen

3) 2- Chromium

4) 7- Oxygen

Step 3

Count the number of each type of

atom in the product.

(NH4)2Cr2O7 Cr203+N2+H2O

1) 2- Nitrogen 2- Nitrogen

2) 8- Hydrogen 2- Hydrogen

3) 2- Chromium 2- Chromium

4) 7- Oxygen 4- Oxygen

Step 4

Note which atoms are not balanced.

(NH4)2Cr2O7 Cr203+N2+H2O

1) 2- Nitrogen 2- Nitrogen

2) 8- Hydrogen 2- Hydrogen

3) 2- Chromium 2- Chromium

4) 7- Oxygen 4- Oxygen

Step 5

Select an atom to balance.

(NH4)2Cr2O7 Cr203+N2+H2O

1) 2- N 2- N

2) 2) 8- H 2- H

3) 2- Cr 2- Cr

4) 7- O 4- O

X 4

Step 5

Select an atom to balance.

(NH4)2Cr2O7 Cr203+N2+ H2O

1) 2- N 2- N

2) 2) 8- H 2- H

3) 2- Cr 2- Cr

4) 7- O 3- O + 4 O =7

X 4 = 8

4