Bell Ringer 2/25Given the materials listed, how can you build the tallest tower possible that is able to support a golf ball?(complete on tower sheet)

Announcements:• If you missed class yesterday, you missed a test.• Need volunteer hours or feeling nice? I need people to help babysit on Monday evening (5:45p-8p) for parent university.

Tall Tower Challenge• You are given the challenge of building the

tallest tower you can build using only straws, pipe cleaners, and paperclips.

• your tower must support the weight of a golf ball for two minutes.

• The golf ball must be supported near the top of the tower, with the bottom of the ball no more than 20% below the upper height of the tower.

Chemical Reactions

• Our goal is achieve balance in our towers. How well did your group do at meeting this challenge?

• How will you improve your tower to make it better?

Announcements:• Need volunteer hours or feeling nice? I need people to help babysit on Monday evening (5:45p-8p) for parent university.

Bell Ringer 2/26

Bell ringer 2/27

• Cute or cruelty to hamsters?

Bell Ringer 3/2• Identify the elements and the numbers of

atoms in each compound:

• Ag2Cl3• 3NO3

• 2Na2(SO4)

• 5Mg(SO4)2

• Have your counting atoms ws out so I can check it.

• If you are coming to help baby-sit tonight, its 5:45p at Southwest Elementary

Balance

• Our goal for our new unit is balance.

Introduction:  Why Balance?

• There's no magic in chemistry. Everything has to come from somewhere. Matter cannot just appear from nowhere.

• In chemistry, we start with reactants to get products. • The amount of products made are so important to

science, industry, and even life that there is an entire discipline called stoichiometry.

• One of the first steps to understanding stoichiometry is making sure all chemical equations are balanced.

Parts of a Chemical Equation

Examples of Chemical Equations

Phase SymbolsIn a balanced equation we will now begin to use phase symbols to indicate the physical state of the reactants/ products.

There are 4 phase symbols:(s): solid(l): liquid(g): gas(aq): aqueous. This means dissolved in water to form a homogeneous solution. By definition any soluble compound will have the (aq) phase symbol in a reaction where water is present. Soluble= (aq), Insoluble= (s).

Law of Conservation of MatterMatter cannot be created nor destroyed.

Rules for balancing

1 Write the correct formulas for all the reactants and products

2 Count the number of atoms of each type appearing on both sides

3 Balance the elements one at a time by adding coefficients (the numbers in front)

4 Check to make sure it is balanced.

Never

• Change a subscript to balance an equation.

• If you change the formula you are describing a different reaction.

• H2O is a different compound than H2O2

• Never put a coefficient in the middle of a formula

• 2 NaCl is okay, Na2Cl is not.

Balancing Hints• Only place coefficients in front. • Never, never, never (and I mean NEVER) change the

subscripts after the correct formula is written. • For single and double replacement reactions, balance the polyatomic ions as a whole item if they appear on both sides of the equation. • For single and double replacement reactions, change H2O to HOH and balance H+ ions and OH- ions. • Balance lone elements first. Lone elements are ones that only appear in one formula on each side. Leave the ones that appear more than once on a side until last. • When you are done, the coefficients need to be in the lowest possible ratio. Always recheck this. • Recheck that all atoms are balanced when you are done.

Practice__ H2 + ___ O2 ___ H2O

__ SO2 + ___ O2 ___ SO3

Answers

2 H2 + O2 2 H2O

2 SO2 + O2 2 SO3

Bell Ringer 3/3Balance these equations• __ Mg + __ O2 → __ MgO

• __ KClO3 → __ KCl + __ O2

• __KOH + __ H3PO4 → __ K3PO4 + __ H2O

 

ANSWERS

• 2 Mg + O2 → 2 MgO

• 2 KClO3 → 2 KCl + 3 O2

• 3 KOH + H3PO4 → K3PO4 + 3 H2O  

Writing Chemical Equations

Writing Chemical Equations2 NO(g) + O2(g) → 2 NO2(g)

• Nitrogen monoxide gas reacts with Oxygen gas to produce nitrogen dioxide gas.

UV

Let’s Practice #1

Let’s Practice #2

Bell ringer 3/4

• Write the word equation for the following reaction:

• __KOH + __ H3PO4 → __ K3PO4 + __ H2O

• __ KClO3 → __ KCl + __ O2

Bell Ringer 3/5

• Sulfur dioxide reacts with oxygen gas to form Sulfur trioxide.

• Methane (carbon tetrahydride) reacts with oxygen gas to form carbon dioxide and water.

Upcoming Schedule• Tomorrow: Kavonne, Kalyn, Josiah, &

Isaac are teaching about chemical reactions.

• Monday: Start collecting data for the inquiry lab. Review for Quiz. I will be checking the word equations/ balancing/ mass ws.

• Tuesday: Quiz. Finish collecting Data and making conclusions for inquiry lab.

• Lab Reports are Due Thursday.

Conserving Mass• Matter cannot be created nor

destroyed.

• This means that the mass of the products must equal the mass of the reactants.

Practice• A 10 g sample of magnesium reacts with

oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted?1. What are the reactants?

2. What are the masses of each reactant?

3. What are the products?

4. What are the masses of each reactant?

5. What is our unknown?

6. What do we need to do to figure out our unknown?

Dehydration of Sugar

• What are the signs that a chemical reaction occurred?

C₁₂H₂₂O₁₁ → 11 H₂O↑ + 12 C

HSO4

Open vs. Closed Systems

• Open system: allow interactions between its internal elements and the environment. Matter & energy can be exchanged between the system and the surroundings.

Example: The classroom

• Closed system: the system is isolated from the environment. Matter and energy cannot be exchanged between the environment and the surroundings.

• Example: A sealed, insulated canister

Why Sulfuric Acid Turns Sugar Black• Table sugar is actually two sugars in one—a disaccharide. It is commonly known as sucrose. Sucrose is a combination of fructose,

a sugar found in fruits, and glucose, known also as blood-sugar, grape-sugar, and corn-sugar. Its chemical formula is C₁₂H₂₂O₁₁. The way these atoms are attached to each other by chemical bonds constitutes its structural formula.

• In the Left Corner…• Most sugar from a grocery store is granular and pure white. If the grains are large enough—existing as large crystals—it is

immediately apparent that sugar isn’t even white; it is totally colorless and transparent. Sold at candy stores, we call it rock candy.• In the Right Corner…• Concentrated sulfuric acid is thick and nearly colorless—oily—much like the Karo Syrup one puts on pancakes. It is an extremely

dangerous acid and dehydrating agent, capable of inflicting severe burns. One of my college chums, working in a laboratory during a work-cooperative assignment, caught just the bottom of a large bottle of the stuff on a laboratory bench. It landed on his blue-jeans. In just seconds he was under a safety shower. Yet, he suffered 3rd-degree burns!

• Let the Fight Begin!• Pour some concentrated sulfuric acid¹ into a beaker containing sugar granules, and a dramatic reaction takes place.² The sugar

turns brown, then changes to black. The volume of the sugar increases greatly. What happened? What’s the black stuff and what is the mist? Why is the beaker so hot?

• Knockout: What Happened?• The heat is due to the release of a tremendous amount of energy. All that heat vaporizes water producing steam—the mist is

mostly water.³ Be careful to avoid the mist, as it doubtless contains traces of acid. Did you notice from the structural formula of sucrose that it contains atoms of hydrogen and oxygen? Combine them, and you get the water, formula H₂O.

• Just one molecule of sucrose contains 11 molecules of water. If you take those out, all that remains of a sugar molecule are 12 atoms of carbon. The black residue is mostly carbon and excess acid.

• Concluding Remarks• Sulfuric acid is a super-strong dehydrating agent, it sucks up water, or the components needed to produce it. Hence, the ether

groups (-C-O-C-) and hydroxyl groups (-OH) in sucrose are stripped away. The overall reaction is written:• C₁₂H₂₂O₁₁ → 11 H₂O↑ + 12 C• Turned to water and carbon, the sulfuric acid turns sugar black.

Bell Ringer 3/9

• Complete questions #1-6 on the review guide.

• Have your balancing equations/ word equations/conservation of mass ws out so that I can check it.

Announcements:• Quiz tomorrow.• Lab Report Due Thurs.• Deadline for retakes= 3/19

Bell Ringer 3/10

• What is the purpose of the Law of conservation of mass?

• How can you demonstrate it in an experiment?

• Have your conservation of mass ws & concept map out so that I can check it.

Announcements:• Quiz today• Lab Report Due Thurs.• Deadline for retakes= 3/19

Today• Work on writing the procedure for your open and

closed experiments with alka seltzer.

• This should be a step-by-step procedure, NOT a paragraph.

• You need a labeled diagram of your set-up.• Make sure you include how you are measuring

the mass.• You will use a ½ a tablet of alka seltzer for each

trial.

Announcements:

If you missed yesterday, you have a quiz to make up.

Bonding retakes must be done by 3/19

Bell ringer 3/16

Describe what you see.

Types of Chemical Reactions

There are 5 types of chemical reactions that we will focus on this semester:

1. Synthesis

2. Decomposition

3. Single Replacement (displacement)

4. Double Replacement (displacement)

5. Combustion

Types of Chemical Rxns

Synthesis

Two or more reactants join together to make products that are fewer in number but larger in atom count. A + B AB

Decomposition

A reactant breaks apart to form products that are greater in number but smaller in atom count. Synthesis and Decomposition are the reverse of one another. AB A + B

Bell ringer 3/17

1. Write out word equations for numbers 3 & 4 under decomposition and numbers 1 & 4 under synthesis.

If you hadn’t already noticed, the synthesis picture/ equation on your note sheet is wrong. It should look like:

Single Replacement

• An Uncombined element “replaces” an element in the compound that is the most chemically similar.

• A metal will replace another metal and a nonmetal will replace a another nonmetal.

• AB + C CB + A

Bell ringer 3/18

Write out word equations for #3 & 4 under single replacement and #1 & 3 under double displacement.

Announcements:Last day for bonding retake is tomorrow.

Lab on Tuesday/ Wednesday(?)- Closed-toe shoes a must!

Double Replacement

• Two compounds react to form two new compounds.

• The 2 ions of the same charge switch places. • For ionic compounds, metals must replace

metals and non-metals must replace non-metals.

Combustion

• CxHy + O2 CO2 + H2O

• What are the three things required to make fire?

A fuel, oxygen, a spark.

the process of burning something.

Bell ringer 3/19

Write out word equations for #1 & 3 under combustion.

Announcements:Last day for bonding retake is today.

Lab on Tuesday/ Wednesday(?)- Closed-toe shoes a must!

Classify the reactions from the balancing equations packet.

The beauty of chemical reactions

Try to balance this reaction:__Al(OH)3(s) + __H2SO4(aq) __Al2(SO4)3(aq) + __H2O(l)

Al

S

H

O

Al

S

H

O

1

1

5

7

2

3

2

13

12

18

8

2 3 6

2

10

3

12

18