10 things about you - carbonear · pdf file•at their core, reactions involve taking...
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Physical and Chemical Properties
Physical Property:
a characteristic of the substance that can be used to identify it
• state (at room temperature)• melting / freezing point• boiling / condensing point• hardness• odor
Chemical Property:
a characteristic behaviour during interactions with other substances
• heat of combustion• stability• flammability• halflife
Physical Change:
a change that does not alter the chemical composition
• state changes• physically breaking, cutting or molding
Chemical Change
a change that alters the chemical composition of a substance
• making KoolAid• burning paper• rusting
3
Chemical
PhysicalPhysical
Physical
Chemical
Chemical
Identify each of a physical or chemical change
4
Properties of Ionic and Molecular Compounds
Ionic Compounds
• solids
• made of ions (ionic bonds)
• high melting and boiling points
• conduct electricity when dissolved / melted (electrolytes)
• many soluble in water
Molecular Compounds
• gasses, liquids, or solids
• made of molecules (covalent bonds)
• low melting and boiling points
• poor conductors (any phase)
• not soluble in water
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Properties of Acids and Bases
Acids
• sour
• corrosive
• turns blue litmus paper red
• pH less than 7 (pH < 7)
• reacts with metals to produce hydrogen gas
Bases
• bitter
• slippery
• turns red litmus paper blue
• pH greater than 7 (pH > 7)
Examples of Acids
• vinegar / acetic acid HC2H3O2
• orange juice / citric acid HCHO7
• aspirin (ASA) / acetylsalicylic acid HCHO4
• sour milk / lactic acid HC3H5O3
Examples of Bases
• baking soda / sodium bicarbonate NaHCO3
• soap / potassium hydroxide KOH
• drain cleaner / sodium hydroxide NaOH
• antacids / aluminum hydroxide Al(OH)3
a pH of 7 is known as a neutral substance
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• a logarithmic scale starting at 7 that measures from 0 14
• a pH between 0 7 is an acidic substance, with 0 being the strongest
stomach acid (pH = 1.5) is highly acidicblack coffee (pH =5.0) is slightly acidic
• a pH between 7 14 is an alkaline (basic) substance, with 14 being the strongest
drain cleaner (pH = 13.5) is highly basicbaking soda (pH = 8.2) is slightly basic
• it is logarithmic in that a difference of 1 is actually a change of 10 times• a difference of 2 would represent a change of 100 (10 x 10)
Ex) How much stronger than Pepsi (pH 2.5) is battery acid (pH 0.5) ?
Ex 2) Baking soda has a pH of 8.4 while drain cleaner has a pH of 13.5.
a) Which is stronger?
b) How much stronger is it?
pH scale
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• acids and bases are ionic compounds that become dissociated in water
• this is known as an aqueous state
• for acids there will be an H+ ion that provides the strength of the acid
• for bases there will an OH ion that provides the strength of the base
• when acids and bases combine the H+ and OH mix to create water
• if done properly the solution will become neutral, or at least closer to neutral
• the remaining ions produce a solid ionic salt (typically not table salt)
• there can also be some other byproducts, especially when weak acids and bases are involved
Neutralization
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Chemical Tests
there are four common tests to determine an unknown vapor
1. Oxygen a glowing splint will reignite
2. Hydrogen a flaming splint will make a "popping" sound
3. Carbon Dioxide a flaming splint will be extinguished
4. Water Vapour / Steam cobalt chloride paper will turn from blue to pink
What is the additional byproduct in the vinegar and baking soda reaction?
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Reactions
• reactions happen when elements / compounds interact
• at their core, reactions involve taking things apart or putting things together
• reactions are represented by equations, which can be seen as a recipe for the desired reaction
Making a Sandwich
ingredients
equation
• the ingredients that go into the recipe are called the reactants while the outcomes of the recipe are called products (in this case the sandwich)
• note that the equation does not include any instructions, nor tools needed
• this particular type of equation is a word equation (no chemical formulas) and does not include any amounts of materials to be used
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Write your own food equation
• some fine points to note
> reactants are always written on the left> products are always written on the right> reactants and products are separated by an arrow> multiple reactants, or multiple products, are separated by
addition signs> items that allow the reaction to occur, but are not changed
by the reaction, are not included in the equation
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Conservation of Mass/ Matter
• in chemical reactions, aside from nuclear reactions, mass is conserved
• in the case of making a sandwich, if I use 200 g of meat, 100 g of bread and 50 g of condiments, my sandwich should have a mass of 350 g (100 + 200 + 50)
• the same should be true with eating the sandwich
• as the sandwich breaks down, 350 g of material should be added to my body
After eating just over 2 pounds of food, do you gain just over 2 pounds? Explain your choice.
• Matter, and therefore mass, cannot be created or destroyed in a chemical reaction
• furthermore, the atoms involved cannot change
• forms are allowed to be changed
• in a nuclear reaction, the matter is changed into energy, so it is still technically conserved
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Endothermic and Exothermic Reactions
Endothermic takes heat in as a reactant
• endothermic reactions feel cool / cold to the touch as they remove heat from the environment
• examples> chemical ice pack> photosynthesis> sweating (evaporation of water)> baking / cooking
Exothermic gives heat off as a product
• exothermic reactions feel warm / hot to the touch as they give heat off to the environment
• examples> chemical hot pack> glow sticks> cellular respiration> combustion P
otential Energy Reactants
Products
Heat is Released
Potential Energy
ReactantsHeat is Absorbed
Products
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Reaction Types
Based on the video, write your own definitions for the following:
Synthesis:
Decomposition:
Single Replacement:
Double Replacement:
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1) Synthesis / Composition: elements combine into one compound
Ex) zinc + oxygen zinc oxide
iron + sulfur _______(II)_________
nitrogen + ________________ ammonia
• more complex synthesis can occur with compounds joining into one compound
2) Decomposition : a compound breaking down into elements
Ex) hydrogen peroxide (H2O2) water (H2O) + oxygen
water hydrogen + _______________
_______________ potassium + chlorine
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4) Double Replacement / Double Displacement: elements within two compounds switch
Ex) copper (II) chloride + silver nitride copper (II) nitride + silver chloride
potassium bromide + silver nitride potassium nitride + ______________
________________ + iron (II) chloride iron (II) hydroxide + sodium chloride
• an acid base neutralization is just a special case of a double replacement
3) Single Replacement / Single Displacement: an element takes the place of another in a compound
Ex) hydrogen chloride + zinc zinc chloride + hydrogen
calcium bromide + fluorine calcium fluoride + __________
________________ + chlorine iron (II) chloride + iodine
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5) Hydrocarbon Combustion: a hydrocarbon (a compound with hydrogen and carbon) is ignited in the presence of oxygen creating carbon dioxide and water vapour
Ex) methane (CH4) + oxygen carbon dioxide + water
butane (C4H10) + __________ carbon dioxide + water
pentane (C5H12) + oxygen ___________ + water
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3) iron + oxygen iron (III) oxide
Identify the type of reaction.
1) zinc oxide zinc + oxygen
2) sodium chloride + fluorine sodium fluoride + chlorine
5) barium chloride + sodium sulfate barium sulfate + sodium chloride
4) propane (C2H8) + oxygen carbon dioxide + water
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Understanding Equations
• chemical equations are most commonly written as with chemical formulas, not names
Ex) iron + oxygen iron (II) oxide
• a chemical equation that not does give the amounts of each substance needed is called a skeleton equation
• most of our work in this section involves turning skeleton equations (no amounts) into balanced equations (proper amounts)
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skeleton equation: H2 + N2 NH3
balanced equation: 3 H2 + N2 2 NH3
3 hydrogen in groups of 2
6 hydrogen total
1 nitrogen in groups of 2
2 nitrogen total
2 ammonia • contains nitrogen in groups of 1
2 nitrogen total• contains hydrogen in groups of 3
6 hydrogen total
Synthesis of hydrogen and nitrogen to produce ammonia
word equation: hydrogen + nitrogen ammonia
visual representation
3 H2
H NH
2 NH3
H H
H H
+ N2
N
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2 Fe + O2 2 FeO
Fe
O OFe
Synthesis of iron and oxygen to produce iron (II) oxide
word equation: iron + oxygen iron (II) oxide
skeleton equation: Fe + O2 FeO
balanced equation:
Reactants Products
Fe:
O:Fe:
O:
visual representation
2 FeO2 Fe + O2
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Are the following equations balanced?
1) 2 Al + 3 FeO Al2O3 + 2 Fe
2) Fe2O3 + H2 2 Fe + H2O
3) Zn + 2 HCl ZnCl2 + H2
22
Balancing Equations
• change the amounts of each reactant and product until all elements show up in equal amounts
• there is not an exact method for this, but over time you will recognize patterns that will help
• work with one element at a time and update your count as you work (pencil recommended)
Ex) _____ Sn + _____O2 _____ SnO
Ex 2) _____ Zn + _____S _____ ZnS
Ex 3) _____ H2 + _____P _____ PH3
Ex 4) _____ HgO _____ Hg + _____ O2
Ex 5) _____ Fe + _____ Cl2 _____ FeCl3
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Balancing With Polyatomic Ions
• when dealing with equations with polyatomic ions, the ions can be grouped and treated as a single object
Ex)
_____ FeCl3 + _____ NaOH ⇒ _____ Fe(OH)3 + _____ NaCl
Ex 2) _____ H2SO4 + _____ NaNO2 ⇒ _____ HNO2 + _____ Na2SO4
Ex 3) _____ AlBr3 + _____ K2SO4 ⇒ _____ KBr + _____ Al2(SO4)3
Fe:
Cl:
Na:
OH:
Fe:
Cl:
Na:
OH:
H:
SO4:
Na:
NO2:
H:
SO4:
Na:
NO2:
Al:
Br:
K:
SO4:
Al:
Br:
K:
SO4:
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