Bellwork: Thursday 4/12/12Take out Packet 10. Discuss your homework questions with students at your group. Be

KIND to all ideas. We will share as a class in about 5 minutes.

1. Discuss the ethics of cloning only the best and brightest of the human race.

2. If you were in charge of undertaking a cloning project, which qualities would you look for when selecting your cloning subjects? Explain why.

Chemistry Review• Atom- smallest particle of an element with

the same properties as that element– In size the entire atom has been thought to be

approximately four-billionths of an inch, meaning that approximately 250,000,000 atoms of this size must be put into line to span 1 inch.

• Element- matter made of one type of atom; cannot be broken down by chemical or physical means

Compound vs. Molecule• Compound- matter made of two or more different

elements; chemically bonded; cannot be separated by physical means; has properties different from elements that make it up– 6.2- THE STUDENT WILL EXPLAIN THAT COMPOUNDS FORM

WHEN TWO OR MORE DIFFERENT KINDS OF ATOMS BOND.

• Molecule- matter made of two or more elements (same or different); smallest particle of a substance with the same properties as that substance– Heteroatomic molecule- must have more than one type of atom,

such as water (H2O) and carbon dioxide (CO2).– Homoatomic molecule- a molecule consisting of atoms of the

same element; i.e. diatomic

Types of Molecules• Diatomic Molecule- simplest molecule; two of the

same atoms bonded together– H2 O2 F2 Br2 I2 N2 Cl2 • HOFBrINCl twins• I Have No Bright Or Clever Friends • Hydrogen; the rest form a 7 on the periodic table: N, O, F

across, then going down Cl, Br, I.

• Polyatomic Molecule- Molecules containing more than two atoms are termed polyatomic molecules, e.g., carbon dioxide (CO2) and water (H2O). – 6.4- THE STUDENT WILL COMPARE AND CONTRAST

MOLECULES AND COMPOUNDS.

Physical and Chemical Changes are two basic ways that matter can change

Think of elements as letters, and compounds as words:

Physical Change

– Printing the same word in a different type without changing the word

Chemical Change

– Rearranging the letters of the original word to make one or more new words

– The new substances formed during a chemical change always have their own set of properties

stampedes stampedes stamp

edesmade steps

Physical Properties and Physical ChangesPhysical Property• observed with the senses (color, shape, odor, state/phase of

matter)• phase changes (melting point, boiling point, freezing point)

Physical Change• Physical changes are about energy and states of matter– You can cause physical changes with forces like motion,

temperature, and pressure. • MATTER: – Alters the form or appearance of a material– Does not make the material into a new substance; the matter is

the same before and after the change– Original matter can be recovered; change can be “undone”

Physical Changes• PARTICLES: – The molecules of the substance are rearranged,

NOT atoms

• EXAMPLES:– chopping wood, bending copper wire into new

shapes, painting a car, ice melting into water

Chemical Properties and Chemical ChangesChemical Property• Observed during a chemical reaction; the way it reacts to another

substance• Based on the structure of the atoms or molecules

Chemical Change• any change that results in the formation of new substances• MATTER:– The matter is different; the original matter is no longer present

and cannot be recovered; the change cannot be “undone”– The substances present at the beginning of the change are not

present at the end

Chemical ChangesPARTICLES• Bonds between atoms in molecules are broken, atoms are rearranged,

and new bonds are made• Forms a new substance with molecules with a different structure• contains the same elements, but rearranged in new combinations– Synthesis Reaction: Element + Element Compound

X + Y XY– Decomposition Reaction: Compound Element + Element

XY X + Y– Single Displacement Reaction: Compounds Compounds

A + XY AY + X– Double Displacement Reaction: Compounds Compounds

XY + AB XB + AY

EXAMPLES: Rusting of iron (oxidation), burning of gasoline in an engine (flammability)

Flammable vs. Combustible

• Flammable- material that can easily catch fire under normal circumstances and with the help of minimal ignition source. Just a spark is sufficient enough– Flash point: below 100°F– Example: gasoline, propane

• Combustible- material that will burn; but more vigorous conditions are required for an ideal combustible material to burn; A simple spark is definitely not enough. – Flash point: above 100°F– Example: paper, wood

• The distinction is determined by how easily they ignite • Flash point- the lowest temperature at which it can

produce a flame when a source of ignition is present.

Differentiating between physical and chemical properties… hold up 1 finger for physical, 2 fingers for chemical

1. Physical Property 2. Chemical Property

The color of the house is red.Oxygen is a gas.A flagpole is 25ft tall.

Copper conducts electricityIron reacts with water to form rust.

Steel is attracted to a magnet. Silver reacts with moisture in the air to form tarnish.

Physical Chemical

1. Sulfur has a yellow color (Color)2. Aluminum has a low density (Density)3. Wood is combustible (Combustibility)4. Zinc reacts with Sulfuric acid to form H2 (Hydrogen gas)

5. Gasoline burns in the presence of oxygen (Flammable)6. Sour Patch Kids ®candy has a sour taste (Taste)7. Water melts at 0 degrees Celsius (Melting point)8. Sodium (Na) + water (H2O) react to form Sodium hydroxide (NaOH) + Hydrogen gas (H2)

9. Sodium hydroxide (NaOH - a base) + Hydrochloric acid (HCl) react to form water (H2O) + salt (NaCl)

10. Diamonds are capable of cutting glass (Hardness)11. Water boils at 100 degrees Celsius (Boiling point)12. Acetic acid (C2H4O2) can neutralize a base

13. Pyrite, aka Fool’s Gold, has a metallic luster (Luster)14. Arsenic’s odor is similar to garlic (Odor)15. Baking soda, aka Sodium bicarbonate (NaHCO3), reacts with vinegar (HC2H3O2) to produce Carbon dioxide gas (CO2)

16. Antimony has a flaky, crystalline texture (Texture)17. An ounce of gold can be hammered into a square sheet 100 feet on each side (Malleability) or

drawn into a wire that would stretch 5 miles (Ductility)18. Silver’s ability to oxidize gives it a unique look, popular in jewelry making (Oxidation)19. Water can be separated by electrolysis into hydrogen and oxygen (2 H2O(l) → 2 H2(g) + O2(g)

20. Mercury is liquid at room temperature (State of Matter)

6.13- TSW CLASSIFY SUBSTANCES USING THEIR PROPERTIES.

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Evidence that a Chemical Change has Occurred: Page 4

1. Bubbles of gas appear2. A precipitate (solid) forms3. A color change occurs4. The temperature changes5. Light is emitted6. A change in volume occurs7. A change in electrical conductivity occurs8. A change in melting point or boiling point occurs9. A change in smell or taste occurs

Homework: Packet 11, Page 3Due tomorrow

Physical vs. Chemical Changes• BOTTOM: Choose 2 examples of physical changes,

and 2 examples of chemical changes. Explain why you chose chemical or physical. Support your

explanation with examples or proof.

Burning trees are chemically

changed into other substances like carbon and

ash.

Bellwork: Friday 4/13/2012

• List (2) possible observations that might make Angelina think she observed a physical change.– No change occurs in the

identity of the substance– Color changes– Size/Shape changes– Phase changes (solid, liquid,

or gas/condensation)

• List (9) possible observations that might make Angelina think she observed a chemical change.– Atoms are rearranged to form

different substances1. Bubbles of gas appear2. A precipitate (solid) forms3. A color change occurs4. The temperature changes5. Light is emitted6. A change in volume occurs7. Electrical conductivity change8. Melting/boiling point change9. Odor or taste change

Angelina performed two chemistry experiments in her science class. In the first experiment, she thought she observed a physical change.

In the second experiment, she thought she observed a chemical change.

Changes in Energy in Chemical Reactions

• Endothermic- energy is absorbed –Ex. Cold pack, baking bread

• Exothermic- energy is released–Ex. Burning gasoline, fireworks

Chemical and Physical Change EquationsPhysical:

G + B GB

Same atoms on both sides of the equation

Chemical:A + B C

Different substances on both sides of the equation.

A & B on the left form a completely different substance C on the right.

Reactants: left side (what is reacting; A & B)

Products: right side (what is produced; C)

Law of Conservation of Mass• Matter can neither be created or

destroyed, but can be changed in form.

• The total mass of the material(s) before the reaction is the same as the total mass of material(s) after the reaction.

Mass of Reactants =Mass of Products

• “+” read as “plus”– Separates molecules on the same side

• “” read as “yields”– Separates reactants (left); products (right)

• Numbers in front: coefficients• Physical states of compounds

• Solid (s)• Liquid (l)• Gas (g)• Aqueous solution (aq)

• Escaping gas ()• Change of temperature ()

Symbols Used in Equations

Types of Chemical Reactions• Synthesis Reaction: Element + Element Compound

X + Y XY• Decomposition Reaction: Compound Element +

ElementXY X + Y

• Single Displacement Reaction: Element + Compound Compound + ElementA + XY AY + X

• Double Displacement Reaction: Compound + Compound Compound + CompoundXY + AB XB + AY

Synthesis

Decomposition

H2CO3 H2O + CO2

2 Na + Cl2 2 NaCl

Double Displacement

Single Displacement

NaCl + AgF NaF + AgCl

Zn + 2HCl ZnCl2 + H2

REVIEW: Law of Conservation of Mass- Packet 12, Page 4• Matter is never created or destroyed in chemical

reactions. The particles of one substance are rearranged to form a new substance.

• The same number of particles that exist before the reaction exist after the reaction.

• Why do we need a rubber stopper in the flask?

Mass of Reactants = Mass of Products

Chemical Equations• Charcoal used in a grill is Carbon. Carbon

reacts with oxygen gas to make carbon dioxide. • What is the chemical equation for this

reaction?

C + O2 CO2–This reads “carbon plus oxygen gas

react to yield carbon dioxide”

Because of the Law of Conservation of Matter, an equation must be balanced.

It must have the same number of atoms of the same kind on both sides.

Balancing Chemical Equations

1. Write correct formula for reactants & products. 2. Find the # of atoms for each element on the left and

right. 3. Add coefficients in front of formulas so the left has the

same # of atoms as the right • HINT: Work on one element at a time • DO NOT CHANGE THE FORMULAS!• You may not change the subscripts• Changing the subscripts changes the compound.

4. Check your answer to see if:– The # of atoms on both sides of the equation are

now balanced– The coefficients are reduced to the least common

factor

Steps to Balancing Equations- Page 5

1. Correct Formula

2. Find # of atoms on left and right• List atoms involved on each side of the arrow• Count up the atoms on each side

3. Add coefficients- adjust totals• Totals still aren’t equal• Add coefficients- adjust totals

4. Check Answers

Mg

O

Mg + O2 MgO1

1

1

2 2

22

22

BOTH SIDES HAVE EQUAL NUMBERS OF

ATOMS

WE SAY THAT THE EQUATION IS BALANCED!!

What type of rxn is this?

Synthesis- S

Fe3O4 + 4 H2 3 Fe + 4 H2O

1. Number of H atoms in 4 H2Oa) 2 b) 4 c) 8

2. Number of O atoms in 4 H2O a) 2 b) 4 c) 8

3.Number of Fe atoms in Fe3O4

a) 1 b) 3 c) 4

Balancing Equations Quick Check

Practice Balancing Equations

1. Mg + N2 Mg3N2

a) 1, 3, 2 b) 3, 1, 2 c) 3, 1, 1

3 Mg + N2 Mg3N2

2. Al + Cl2 AlCl3

a) 3, 3, 2 b) 1, 3, 1 c) 2, 3, 2

2 Al + 3 Cl2 2 AlCl3

Balance each equation. The coefficients for each equation are read from left to right What type of rxns

are these?

Synthesis- S

Synthesis- S

Fe2O3 + C Fe + CO2

a) 2, 3, 2, 3 b) 2, 3, 4, 3 c) 1, 1, 2, 3 2 Fe2O3 + 3 C 4 Fe + 3 CO2

Al+ FeO Fe + Al2O3

a) 2, 3, 3, 1 b) 2, 1, 1, 1 c) 3, 3, 3, 1 2 Al + 3 FeO 3 Fe + Al2O3

Al+ H2SO4 Al2(SO4)3 + H2

a) 3, 2, 1, 2 b) 2, 3, 1, 3 c) 2, 3, 2, 3

2 Al + 3 H2SO4 Al2(SO4)3 + 3

H2

What type of rxns are these?

Single Displacement- SD

Single Displacement- SD

Single Displacement- SD

Burning of PropaneC3H8 + 5O2 3CO2 + 4H2O 1, 5, 3, 4

Combustion of Hydrogen and Oxygen, which is a commonly used reaction in rocket engines:

2H2 + O2 → 2H2O 2, 1, 2

Combustion reaction with Fluorine as an oxidizing agent:CH2S + 6F2 → CF4 + 2HF + SF6 1, 6, 1, 2, 1

Burning of MethaneCH4 + 2 O2 → CO2 + 2H2O 1, 2, 1, 2

Photosynthesis 6H2O + 6CO2 C6H12O6+ 6O2 6, 6, 1, 6

Homework- Pages 7 & 8: Balancing Chemical Equations & Types of Reactions

• Work silently on these pages