Bellwork: Thursday 4/12/12 Take 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. • Discuss the ethics of cloning only the best and brightest of the human race. • 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 • IHave 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 changeThink 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 stampedes madesteps
Physical Properties and Physical Changes Physical 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 Changes Chemical 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 Changes PARTICLES • 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 • 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. • 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
1. Physical Property 2. Chemical Property Differentiating between physical and chemical properties… hold up 1 finger for physical, 2 fingers for chemical Copper conducts electricity Iron reacts with water to form rust. Oxygen is a gas. The color of the house is red. A flagpole is 25ft tall. Steel is attracted to a magnet. Silver reacts with moisture in the air to form tarnish.
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 • Bubbles of gas appear • A precipitate (solid) forms • A color change occurs • The temperature changes • Light is emitted • A change in volume occurs • A change in electrical conductivity occurs • A change in melting point or boiling point occurs • A change in smell or taste occurs
Homework: Packet 11, Page 3Due tomorrowPhysical 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.
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 substances Bubbles of gas appear A precipitate (solid) forms A color change occurs The temperature changes Light is emitted A change in volume occurs Electrical conductivity change Melting/boiling point change Odor or taste change Bellwork: Friday 4/13/2012 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
Physical: 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. Chemical and Physical Change Equations 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
Symbols Used in Equations • “+” 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 ()
Types of Chemical Reactions • Synthesis Reaction: Element + Element Compound • X + Y XY • Decomposition Reaction: Compound Element + Element • XY X + Y • Single Displacement Reaction: Element + Compound Compound + Element • A + XY AY + X • Double Displacement Reaction: Compound + Compound Compound + Compound • XY + AB XB + AY
2 Na + Cl2 2 NaCl Synthesis H2CO3 H2O + CO2 Decomposition
Zn + 2HCl ZnCl2 + H2 Single Displacement NaCl + AgF NaF + AgCl Double Displacement
REVIEW: Law of Conservation of Mass- Packet 12, Page 4 • Matter is never created or destroyedin 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”
Balancing Chemical Equations 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.
Steps to Balancing Equations- Page 5 • Write correct formula for reactants & products. • Find the # of atoms for each element on the left and right. • 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. • 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
Correct Formula • Find # of atoms on left and right • List atoms involved on each side of the arrow • Count up the atoms on each side • Add coefficients- adjust totals • Totals still aren’t equal • Add coefficients- adjust totals • Check Answers What type of rxn is this? Synthesis- S BOTH SIDES HAVE EQUAL NUMBERS OF ATOMS • Mg + O2 MgO 2 2 WE SAY THAT THE EQUATION IS BALANCED!! 1 1 2 2 Mg O 2 1 2
Balancing Equations Quick Check Fe3O4 + 4 H2 3 Fe +4H2O 1. Number of H atoms in 4 H2O a) 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
Practice Balancing Equations Balance each equation. The coefficients for each equation are read from left to right What type of rxns are these? 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 Synthesis- S Synthesis- S
What type of rxns are these? 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, 2b) 2, 3, 1, 3 c) 2, 3, 2, 3 2 Al + 3 H2SO4 Al2(SO4)3 + 3 H2 Single Displacement- SD Single Displacement- SD Single Displacement- SD
Combustion of Hydrogen and Oxygen, which is a commonly used reaction in rocket engines: 2H2 + O2 → 2H2O 2, 1, 2 Burning of Propane C3H8 + 5O2 3CO2 + 4H2O 1, 5, 3, 4 Combustion reaction with Fluorine as an oxidizing agent: CH2S + 6F2 → CF4 + 2HF + SF6 1, 6, 1, 2, 1 Burning of Methane • CH4 + 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