Presentation on theme: "Improvements Have students write chemical equations from word equations first, then go the other way. And get a worksheet on these things. Specific Examples."— Presentation transcript:
Improvements Have students write chemical equations from word equations first, then go the other way. And get a worksheet on these things. Specific Examples for Rules of balancing Better procession for teaching balancing equations. The worksheet is excellent, but the powerpoint is awful for teaching! Include Steel wool experiment – Put in water – Put in salt water – Measure change in mass – Measure amount of salt! – Compare how fast they rust – Why do things rust faster when they’re wet anyhow?
Today you are going to…take notes on chemical reactions. So you can…interpret, write, and balance chemical equations You’ll know you’ve got it when you can Differentiate between chemical & physical changes Identify the parts of a chemical equation Define, explain, and give examples of precipitates & catalysts
Physical change –a change in the appearance of something, often easier to “undo” – Ex. Chemical change – a substance changes into a new substances with new properties (and new chemical formulas). – Ex.
Chemical Reactions Word Equation – to express the change in words. Chemical equation – to express the change in formulas.
The parts of a chemical equation Reactants – chemicals reacting Products – chemicals produced Coefficients – big numbers, used to balance equation, how many of each compound/molecule Subscripts – part of chemical formula, tells how many of each atom is in chemical Yields – arrow! 2 H 2 0 2 H 2 + O 2
States of Matter in Equations Liquid water decomposes into hydrogen gas and oxygen gas. (s) - solid (l) - liquid (g) - gas (aq) – aqueous solution (dissolved in water) H 2 0 (l) H 2 (g) + O 2 (g)
Precipitate A solid produced by mixing two aqueous solutions – A bunch of precipitates videoprecipitates Lead (II) nitrate in solution reacts with sodium iodide in solution to form lead (II) iodide precipitate and a sodium nitrate solution.
Precipitate You get gold & precious metals from computers via precipitates!
Bell Work 2/7/14 - min 1.Write the equation above in words. (C 10 H 8 is Naphthalene) 2.Identify the following in the equation above. 1.Products, reactants, coefficients, subscripts 3.What is a precipitate? 4.What does aqueous mean? 5.What is a catalyst? C 10 H 8 (l) + 12 O 2 (g) 10 CO 2 (g) + 4 H 2 O (g)
Review Work 2/26 2 CO (g) + O 2 (g) 2 CO 2 (g) 1.Write a word equation for the reaction above. 2.Define catalyst 3.Write the chemical formula of the products & reactants above. 4.What does aqueous mean? 5.Define precipitate 6.Why do equations have to be balanced? (why & what law) Pt
2CO (g) + O 2 (g) 2CO 2 (g) 1.In presence of a platinum catalyst, gaseous carbon monoxide combines with gaseous oxygen nitrogen to form gaseous carbon dioxide. 2.A catalyst is something that speeds up or slows down a chemical reaction without chemically changing itself. 3.Reactants are CO & O 2 Product is CO 2 4.Aqueous means “dissolved in water” 5.A precipitate is the solid formed from a reaction between 2 aqueous solutions. 6.Equations have to be balanced to be physically accurate/true. If they’re not balanced, they show matter either magically appearing or disappearing, which can’t happen. The law of conservation of mass states that matter cannot be created nor destroyed. Pt
Catalysts A substance that changes the rate of a chemical reaction without being consumed or changed significantly – Positive catalysts - speed up reaction Lower the amount of energy required to activate the reaction – Negative catalysts, aka “inhibitors” - slow down reaction Uses – Used in making gasoline, plastics, margarine, beer – In laundry detergents – In living things - enzymes are biological catalysts
Examples of Catalysts Platinum in catalytic convert reduces NO emissions In presence of a platinum catalyst, nitrogen monoxide gas decomposes into nitrogen gas and oxygen gas 2NO (g) N 2 (g) + O 2 (g) Platinum decreases CO emissions 2CO (g) + O 2 (g) 2CO 2 (g) Pt
What’s the word equation? In presence of sulfuric acid catalyst, ethanol gas reacts with hydrochloric acid gas to form chloroethane and liquid water In the presence of a vanadium (V) oxide catalyst, sulfur dioxide gas reacts with oxygen gas to produce sulfur trioxide gas.
Reactants being heated ∆ means the reactants are heated
Elephant Toothpaste Elephant toothpaste demos!demos – H 2 O 2 liquid hydrogen peroxide – NaI – Food coloring – Dish soap
Elephant Toothpaste Elephant toothpaste demos!demos 2 H 2 O 2 (aq) → O 2 (g) + 2 H 2 O(l) NaI
Bell Work 2/11/14 – 5 min N 2 (g) + O 2 (g) N 2 O 5 (l) 1.Write the word equation for the above reaction. 2.What is the reason for balancing equations? 3.What is the big difference between a physical & chemical change? (In a chemical change…) Ni
Bell Work 2/11/14 – 5 min N 2 (g) + O 2 (g) N 2 O 5 (l) 1.In the presence of a nickel catalyst, nitrogen gas and oxygen gas yield liquid dinitrogen pentoxide 2.Conservation of mass – matter can’t be created or destroyed 3.In a chemical change, a new substance with new chemical properties is created. Ni
Today you are going to…take notes on chemical reactions. So you can…classify and balance chemical equations. You’ll know you’ve got it when you can State the Law of Conservation of Mass. Identify & describe the 5 types of reactions. Balance chemical equations.
6 Types of Chemical Reactions Synthesis Decomposition Single-Displacement Double-Displacement Acid-Base Combustion
Synthesis What does synthesis mean? Synthetic? Two or more substances combine to form one. A + B ---> AB One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide: Fe + S 8 ---> FeS
Decomposition What does decompose mean? One complex substance breaks down to make 2 simpler ones. (Opposite of synthesis) AB ---> A + B Ex: Electrolysis of water to make oxygen and hydrogen gas: H 2 O ---> H 2 + O 2
Single-Displacement What does single mean? What does displacement mean? One element trades places with another element in a compound. A + BC ---> AC + B Ex: when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas: Mg + Be(OH) 2 ---> Mg(OH) 2 + Be
Double-Displacement The parts of two substances switch places, forming two new substances. AB + CD ---> AD + CB Ex: the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate: Pb(NO 3 ) 2 + 2 KI ---> PbI 2 + 2 K(NO 3 )
Acid-Base A double displacement reaction that takes place when an acid and base react with each other. Makes water (& usually salt). HA + BOH ---> H 2 O + BA Ex: hydrobromic acid reacts with sodium hydroxide HBr + NaOH ---> H 2 O + NaBr
Give students something Can you turn this into water?
Combustion What does combustion mean? When oxygen combines with another compound (hydrocarbon) to form water and carbon dioxide. These reactions are exothermic, meaning they __________________. Ex: Burning of napthalene: C 10 H 8 (s) + 12 O 2 (g) 10 CO 2 (g) + 4 H 2 O (g)
Candle demo! Pass out candles and jars and ask the groups to make observations...see if they can come to conclusion. So what gases were in the jar? 2 O 2 + CH 4 CO 2 + 2 H 2 O
Combustion Candle demo – Limiting reactant! – Why do we balance equations? – Jar of alcohol? Bubble Soapy hand – Evaporation! Lycopodium powder
Elephant Toothpaste Elephant toothpaste demos!demos 2 H 2 O 2 (aq) → O 2 (g) + 2 H 2 O(l) KI
Schedule Friday – Precipitate Lab Monday – Demos – 1 more worksheet! Tuesday – Review for Test Wednesday – Test
Bell Ringer – 2/12/14 3 Li (s) + AlCl 3 (l) 3 LiCl (aq) + Al (g) 1.In your notes, write the word equation for the chemical reaction above.
Bell Ringer – 2/12/12 3 Li (s) + AlCl 3 (l) 3 LiCl (aq) + Al (g) Solid lithium combined with liquid aluminum chloride yields aqueous lithium chloride and gaseous aluminum.
Schedule Monday – Return Tests! – Chemical Equation Worksheet #1 – Elephant Toothpaste Lab (Turn in) Tuesday – Types of equations notes – Balancing Equations – HW: Finish! Wednesday – Quiz! – Review HW – Practice writing & balancing equations Thursday – Balance equations: computer lab Friday – Preview Precipitate lab – Demos! (Write equations) Monday – Precipitate Lab Tuesday – Review Precipitate lab – Demos – Review for test Wednesday – Review for test Thursday – Test
Law of Conservation of Mass Toasted cheese sandwich example? Come up with better food
Make this with a stick & ball H 2 0 H 2 + O 2
Law of Conservation of Mass Matter cannot be created nor destroyed by ordinary chemical or physical means. Things can’t just appear from nowhere, nor can they cease to exist. There have to be the same number of each atom on both sides of an equation. This is why you have to balance equations.
Bell Work 1/31/13 – 5 min N 2 + O 2 N 2 O 5 1.What type of equation is above? 2.Nickel acts as a positive catalyst in this equation. What does that mean nickel does? 3.How could you change the equation to show that nickel is acting as a catalyst? 4.What is the reason for balancing equations?
Bell Ringer 2/4/13 1.The red 2’s in the above equations are _____. 2.The black 2’s in the above equations are _____. 3.Something that speeds up or slows down a chemical reaction is a _____. 4.The above equation is a _____ reaction. 5.The below equation is a _____ reaction. H 2 + 2 O 2 2 H 2 O C 10 H 8 + 12 O 2 ---> 10 CO 2 + 4 H 2 O
Bell Work 1. H 2 (g)+ N 2 (g) NH 3 (g) 2. Al + H 2 SO 4 Al 2 (SO 4 ) 3 + H 2
1. H 2 (g)+ N 2 (g) NH 3 (g) 2. Al + H 2 SO 4 Al 2 (SO 4 ) 3 + H 2
Bell Work 2/6/13 – 3 minutes Identify & balance 1. SiCl 4 + H 2 O SiO 2 + HCl 2. NH 3 + O 2 N 2 + H 2 O
Bell Work 2/9/13 – 3 minutes Write the word equation and balance it. 1.Solid magnesium combines with oxygen gas to form magnesium oxide. 2.Solid magnesium combines with carbon dioxide gas to form solid magnesium oxide and solid carbon.
1) synthesis – you make only 1 product Example – burning a piece of magnesium ribbon to make magnesium oxide. 2) decomposition – you start with only one reactant that breaks down. Example – heating copper II carbonate to make copper II oxide and carbon dioxide. 3) Single replacement – an element replaces an element in a compound. Example - Adding a metal to an acid to make a metal chloride and hydrogen gas. 4) Double replacement – two elements in two different compounds switch places. Example – any precipitate reaction 5) Combustion - burning a hydrocarbon to produce carbon dioxide & water
Bell Work 2/13/14 – 5 min Balance AND draw the molecules involved below. H 2 O + Fe Fe 2 O 3 + H 2
Identify the type of reaction 1.H 2 + 2 O 2 2 H 2 O 2.C 10 H 8 + 12 O 2 10 CO 2 + 4 H 2 O 3.CO C + O 2 4.Li + AlCl 3 LiCl + Al 5. B 2 Br 6 + H(NO 3 ) B(NO 3 ) 3 + HBr 6.H 2 + O 2 H 2 O 2 7.4 NH 3 + 3 O 2 2 N 2 + 6 H 2 O
How many of each atom are there? CsOH___________________ Na 2 SO 4 ___________________ (CO 3 ) 3 ___________________ Al 2 (SO 4 ) 3 ___________________ Ca(C 2 H 3 O 2 ) 2 ___________________ 2 Mg 3 P 2 ___________________ 3 Na 2 SO 4 ___________________ 2 Ca(C 2 H 3 O 2 ) 2 ___________________
Rules for balancing equations. NEVER CHANGE SUBSCRIPTS! Only change __________. Don’t give up…be persistent! 1.Polyatomic ion rule – if you have a polyatomic ion on both sides of the arrow, put parenthesis around it. 2.First Even/odd rule – if there’s an even number of atoms on one side and an odd number on the other side, multiply the odd number by 2. 3.Identify elements that appear in only one reactant and one product, and balance the atoms of those elements first. 4.Next balance the element with the greatest difference. 5.Lastly balance lone elements!
To know for chemical reaction test Law of conservation of mass Define precipitate & catalyst Parts of a chemical equation Types of chemical equations Balance chemical equations States of matter in chemical equations
4 th pd. Bell Work 1/29/13 – 3 min 1.The red 2’s in the above equations are _____. 2.The black 2’s in the above equations are _____. 3.Something that speeds up or slows down a chemical reaction is a _____. 4.A solid produced by mixing two aqueous solutions is a _____. H 2 + 2 O 2 2 H 2 O
Bell Work 2/13/13 – 3 min 1.H 2 + 2 O 2 2 H 2 O 2.C 10 H 8 + 12 O 2 10 CO 2 + 4 H 2 O 3.CO C + O 2 4.Li + AlCl 3 LiCl + Al 5. B 2 Br 6 + H(NO 3 ) B(NO 3 ) 3 + HBr 6.H 2 + O 2 H 2 O 2 7.4 NH 3 + 3 O 2 2 N 2 + 6 H 2 O Identify the types of the following reactions.
Bell Work 2/5/14 – 3 min Start a new bell work sheet titled “Chemical Reactions”. 1.Give 3 examples of physical changes & 3 examples of chemical changes. 2.What’s the one definite, huge difference between a physical & chemical change?
Bell Work 3/30/11 – 4 min Give one thing that could be evidence of a chemical reaction. (c.s.) 1.Make the following equation true by putting integers (1,2,3…) in the blanks. (___)(2x) = (___)(x + x + x)
Bell Work 3/31/11 – 4 min 1.Write the following equation as a word equation. NaI (aq) + KNO 3 (aq) KI (s) + NaNO 3 (aq) 2.Write the following as a formula equation. Magnesium metal burns in oxygen gas, creating a heat and making a white powder called magnesium oxide. A solution of sodium iodide is added to a solution of potassium nitrate to make a potassium iodide precipitate and a sodium nitrate solution. Mg (s) + O 2 (g) MgO (s) + heat
Bell Work 4/4/11 – 5 min 1.Balance this!N 2 + F 2 NF 3 2.W5SAYW
Bell Work 1/19/12 1.The red 2’s in the above equations are _____. 2.The black 2’s in the above equations are _____. 3.Something that speeds up or slows down a chemical reaction is a _____. 4.A solid produced by mixing two aqueous solutions is a _____. 5.State the law of conservation of mass. 6.Why must equations be balanced? H 2 + 2 O 2 2 H 2 O
Bell Work 4/5/11 – 5 min 1.Balance this! C 6 H 6 + O 2 CO 2 + H 2 O
Bell Work 4/14/11 – 6 min Write the word equatioo;ia w OI EIJP4RT IO4EI
Bell Work 2/22/13 H 3 PO 4 + KOH K 3 PO 4 + H 2 O 1.Write the word equation for the chemical equation above. 2.Balance the chemical equation above.