1/31/12 A/B DayLEQ: What can happen to the reactants in a chemical reaction?

1. What is the difference between a natural material and a synthetic one?

2. Is steel natural or synthetic?3. Is neon natural or synthetic?4. A scientist is looking for evidence of a chemical change. What is one thing he should look for?5. A scientist is looking for evidence of a physical change. What is one thing she should look for?

EOG Question:

Which of the following may happen during a physical change?

A. New substances are formedB. Reactants form productsC. A precipitate is formedD. The temperature may increase

Let’s Review: LAW OF CONSERVATION OF MATTER

Matter can’t be _________ and it

can’t be _____________.

Today’s LEQ: What can happen to the reactants in a chemical reaction?

By the end of today, you should be able to…1. Identify reactants and products

2. Apply the law of conservation of matter to chemical reactions

3. Identify the creation of gases and precipitates as a part of a chemical reaction

How many words can you make using ONLY the letters below?

A A S P M E N R U W T T G O B P

• Past• West• Aspen• Tram• Pan• We• Sat• Men

A A S P M E N R U W T T G O B P

• Brat• Want• Poem• Rap• Part• Sap• Spent• Grant

Elements are like letters, compounds

are like words.

FOCUS VOCABULARY:

90. Chemical Reaction91. Reactant92. Product93. Precipitate

Elements are like letters, compounds are like words.

A CLOSER LOOK AT CHEMICAL CHANGES!

Element + Element

One OxygenAtom

Two Hydrogen

Atoms

+

Water

Compound

Compounds

Explain subscript numbers

2H + O H2O

Chemical Reaction: process of forming new substances (a chemical change!)

DRAW THIS IN YOUR NOTES:

H2O

2H + O H2O

One OxygenAtom

Two Hydrogen

Atoms

+

Water

2H + O H2O

Chemical Reaction: process of forming new substances (a chemical change!)

DRAW THIS IN YOUR NOTES:

2 Hydrogens

1 Oxygen

1 Water

H2O

EOG QUESTION:

Carbon combines with oxygen to form carbon dioxide. What is the word equation for this chemical reaction?

a. carbon dioxide carbon + oxygenb. carbon carbon dioxide + oxygenc. carbon + oxygen carbon dioxided. carbon dioxide + oxygen carbon

2H + O H2O

Chemical Reaction: process of forming new substances (a chemical change!)

DRAW THIS IN YOUR NOTES:

2 Hydrogens

1 Oxygen

1 Water

Reactants Product

H2O

H2O 6 H2O

ONE WATER MOLECULE-2 hydrogens -1 oxygen

6 WATER MOLECULES-12 hydrogens, -6 oxygens

Big Numbers vs. Little Numbers

6 CO2 + 6 H2O C6H12O6 + 6 O2

6 Carbon Dioxides

6 Waters 1 Glucose 6 Oxygenparticles

Reactants Products

Big Numbers vs. Little Numbers

BrainPop: Chemical Equations

In your notes…1. Reactants: Products:2. Reactants: Products:3. Reactants: Products:4. Reactants: Products:

1. 2 H₂0₂ 2 H₂0 + O ₂

2. C3H8 + 5 O2 4 H2O + 3 CO2

3. 4 Al + 3 O2 2 Al2O3

4. 6 CO₂ + 6 H₂OC₆H₁₂O₆ + 6 O₂

Chemical Reactions

Law of Conservation of Matter

Law of Conservation of Matter

Mass of reactants ALWAYS EQUALS the mass of the products!

Example: Reactants = 12 gProducts = 12 g

2H + O H2O

One OxygenAtom

Two Hydrogen

Atoms

+

Water

6 CO2 + 6 H2O C6H12O6 + 6 O2

6 Carbons12 Hydrogens18 Oxygens

6 Carbons12 Hydrogens 18 Oxygens

Reactants Products

REACTANTS = PRODUCTS

EOG QUESTION:

If the mass of the reactants in a chemical reaction is 123.49 grams, what is the mass of the products?

a. 78.49 gramsb. 123.49 gramsc. 246.98 gramsd. impossible to tell

1. 2 H₂0 ₂ 2 H ₂ 0 + O ₂ 12 g _____?_____

2. C3H8 + 5 O2 4 H2O + 3 CO2

4 .5 g + 3.5 g _______?_______

3. 4 Al + 3 O2 2 Al2O3

10 g + _?_ 18 g

4. 6 CO₂ + 6 H₂OC₆H₁₂O₆ + 6 O₂ 75g + 45 g 10g + __?__

EOG QUESTION:

Chemical X has a mass of 5 grams, and chemical Y has a mass of 10 grams. If the two chemicals are mixed and a complete chemical reaction takes place, what is most likely the mass of the product?

a. 5 gramsb. 10 gramsc. 15 gramsd. 50 grams

How is this possible with the law of conservation of matter?

Reactants Products

DEMO: Let’s watch a chemical reaction!

Reactants Products

Chemical Reactions

Mass of reactants ALWAYS EQUALS the mass of the products!

Ex: Reactants = 12 g

Products = 12 g

Law of Conservation of Matter

-chemical reactions can sometimes form a

GAS!

EOG QUESTION:After a chemical reaction occurs in an open test tube, measurements indicate that the mass of the reactants is greater than the mass of the products remaining in the test tube. What most likely explains the measurements?

a. a gas was producedb. a solid was producedc. the salinity of the reactants was highd. the temperature of the reactants was low

What in the world is a precipitate?• http://

www.youtube.com/watch?v=RE-dFN7U91M&feature=related

• http://www.youtube.com/watch?v=pFovlKpPCbI

• http://www.youtube.com/watch?v=Trdyqmzu3JA&feature=related

Chemical Reactions

Mass of reactants ALWAYS EQUALS the mass of the products!

Ex: Reactants = 12 g

Products = 12 g

Law of Conservation of Matter

-chemical reactions can sometimes form a

GAS!

-chemical reactions can also form a PRECIPITATE!(a solid that forms in a solution)

Let’s Practice!

Summarizer:Consider the following: 2 S2O3 + I2 → S4O6 + 2I

1.What are the reactants?2.What are the products?

3.If there are 12 grams of reactants in a chemical reaction, what is the mass of the products?

4.If you create a chemical reaction in an open test tube and the mass of the reactants is MORE than the mass of the products, what happened?!

5.What is a precipitate?