Unit 2 Chemical Reactions. solid copper (l) carbonate + water carbon dioxide gas + copper (l) hydroxide

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Mildred Henry
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1 Unit 2 Chemical Reactions 2.0 Physical vs. Chemical Change Physical Chemical Typical observations of chemical changes: Phase change o melting/freezing o sublimation/deposition o condensation/evaporation Typical observations of chemical changes: New colour New smell Bubbles form (gas produced) Temperature change Formation of precipitate 2.1 Writing Chemical Equations (WB P.77 80) To describe chemical reactions, we can use word equations: solid copper (l) carbonate + water carbon dioxide gas + copper (l) hydroxide Usually chemical reactions are described using chemical equations. It takes too long to use words and word equations don t tell us how many atoms are involved. Cu 2 CO 3(s) + H 2 O (l) CO 2(g) + 2 CuOH (aq) 1 Gu 2016

2 The Law of Conservation of Mass:. All chemical equations must be. Cu 2 CO 3(s) + H 2 O (l) CO 2(g) + 2 CuOH (aq) Element Reactants Products Critical thinking: Fred just learned about the law of conservation of mass and wanted to test it for himself. He found a chemical reaction to use to investigate. He reacts 25 g of reactant X with 5 g of reactant Y. The reaction turned purple, became hot, and he saw some steam. When Fred weighed the products, he found that it weighed only 20 g. Fred decided that his Science teacher was wrong. Rules for writing balanced equations: 1. Coefficients must be whole numbers (no decimals) 2. Never change subscripts 3. Simplify coefficients if you can Tips for success 1. Balance metals first 2. Balance H last 2 Gu 2016

3 Practice: Balance the following skeleton chemical equations 1. Ca 2 C + O 2 Ca + CO 2 2. Pb(NO 3 ) 2 + NaI PbI 2 + NaNO 3 3. N 2 + H 2 NH 3 4. KClO 3 KCl + O 2 5. NaCl + F 2 NaF + Cl 2 6. H 2 + O 2 H 2 O 7. AgNO 3 + MgCl 2 AgCl + Mg(NO 3 ) 2 8. AlBr 3 + K 2 SO 4 KBr + Al 2 (SO 4 ) 3 9. CH 4 + O 2 CO 2 + H 2 O 10. C 3 H 8 + O 2 CO 2 + H 2 O 11. C 5 H 12 + O 2 CO 2 + H 2 O 12. Challenge: C 19 H 17 NO 3 + O 2 CO 2 + H 2 O + N 2 Practice: Write and balance the following chemical reactions 1. zinc + lead (II) nitrate produces zinc nitrate + lead 2. aluminum bromide + chlorine makes aluminum chloride + bromine 3. sodium phosphate + calcium chloride forms calcium phosphate + sodium chloride 4. potassium chlorate when heated produces potassium chloride + oxygen gas 3 Gu 2016

4 2.2 Types of Chemical Reactions (WB P ) Synthesis Two or more elements combine to form a compound Decomposition A single compound breaks down into simpler substances ( reverse synthesis ) Single Replacement An element reacts with an ionic compound and replaces one element in that compound Double Replacement Two ionic compounds react and two metals (or non metals) switch places Neutralization A special type of double replacement where an acid reacts with base to produce salt and water Combustion An organic compound (C, H, sometimes O) burns in oxygen to give carbon dioxide and water 4 Gu 2016

5 Practice: Predict the Products of each reaction and then write the complete and balanced equation. 1. Iron reacts with oxygen 2. Aluminum oxide is heated up 3. C 3 H 8 burns in oxygen 4. Aluminum hydroxide is mixed with potassium sulfide 5. Mg reacts with HNO 3 6. H 2 SO 4 reacts with KOH 7. Iron (ll) chloride is mixed with lithium hydroxide 8. KBr is sprinkled in a chlorine gas chamber 5 Gu 2016

6 2.3 What are Acids and Bases? (WB P.87 88) Acids Bases Where do we find them? Properties Chemical Formula taste will corrode rocks, metals, your skin conductive contains the H + is bonded to an anion and is usually the first one written in the chemical formula taste, is will corrode your skin conductive contains the OH is bonded to a cation and is usually the last one written in the chemical formula. When Mixed with Water ph HCl H + + Cl The more H + an acid releases, the stronger the acid NaOH Na + + OH The more OH a base releases, the stronger the base Practice: Identify if the following compounds are acids, bases, or neither (not acid, not base). Acid Base Neither HCl NaOH HF H 2 O 2 Mg(OH) 2 H 2 SO 4 SiH 4 HNO 3 C 2 H 4 H 2 6 Gu 2016

7 2.4 What is ph? (WB P.84 85, 87 88) ph is what we use to measure how acidic or how basic a solution is. It is a measure of how much there is in solution, or its concentration. VERY ACIDIC VERY BASIC ACIDIC solution BASIC solution NEUTRAL solution H + OH H + H + H + OH H + OH H + OH OH H + H + H + OH OH H + OH OH OH H + H + OH OH H + OH 7 Gu 2016

So, what do the numbers on the ph scale actually mean?

8 Water is actually slightly ionic. It will break down to H + and OH. About 1 in 1 million water molecules will do this. Can you see why water is neutral? So, what do the numbers on the ph scale actually mean? Every 1 ph change = 10x Practice: Calculate the relative acidity of solutions. 1. How much more acidic are tomatoes than eggs? 2. How much more acidic is soap than bleach? 3. How much more acidic is lemon than water? 8 Gu 2016

What is the ph of your saliva? ph indicator Methyl Orange Bromothymol Blue colour change yellow yellow A. 2 B. 5 C. 8 D.

9 A ph indicator is a chemical that changes colour under different ph s. ph indicators can be used to estimate the ph of a solution. Example: Bromothymol Blue Practice: You test your saliva using Methyl Orange and Bromothymol Blue. Below are the results. What is the ph of your saliva? ph indicator Methyl Orange Bromothymol Blue colour change yellow yellow A. 2 B. 5 C. 8 D. 11 Chemical X turns Phenolphthalein pink and Indigo Carmine blue. What is the ph of Chemical X? A. 2 B. 5 C. 11 D Acid Nomenclature (WB P.86, 88) 9 Gu 2016

10 H x IDE Acids or Binary Acids The anion is made of ONE element Acid Formula What is the Anion Name? Acid Name HF HCl HBr HI *H 2 S *H 3 P H x ATE Acids The anion name ends in "ATE" Acid Formula What is the Anion Name? Acid Name H 2 CO 3 HClO 3 H 2 CrO 4 H 2 Cr 2 O 7 CH 3 COOH HNO 3 H 2 C 2 O 4 HClO 4 HMnO 4 *H 2 SO 4 *H 3 PO 4 H x ITE Acids The anion name ends in "ITE" Acid Formula What is the Anion Name? Acid Name HClO 2 HClO HNO 2 *H 2 SO 3 *H 3 PO 3 10 Gu 2016

11 Acid Name Anion Ending is ide, ate, or ite? Anion Must Be Acid Formula hydrobromic acid hydroiodic acid hydrosulphuric acid sulphuric acid chlorous acid acetic acid Practice: Name or write the formula for the following acids HNO 3 H 2 CO 3 H 2 SO 3 H 2 S CH 3 COOH H 3 PO 4 HBr chromic acid hydrofluoric acid phosphoric acid hydrocyanic acid hypochlorous acid permanganic acid sulfuric acid 2.6 Factors Affecting Reaction Rates (WB P ) Rate of reaction: the speed that reactants turn into products In order for reactants to occur, reactant particles must Gu 2016

(dilute) high concentration (concentrated) B.

Surface area acts on # collisions E of collisions low surface area high

Temperature acts on # collisions E of collisions low temperature high

12 A. Concentration: concentration = rate. Concentration acts on # collisions E of collisions low concentration (dilute) high concentration (concentrated) B. Surface Area: surface area = rate. Surface area acts on # collisions E of collisions low surface area high surface area C. Temperature: temperature = rate. Temperature acts on # collisions E of collisions low temperature high temperature D. Catalyst: Adding a catalyst = rate. Catalysts acts on # collisions E of collisions A catalyst is a substance that speeds up reactions without being used up. No Catalyst Catalyst Present 12 Gu 2016

2.7 Nuclear Decay (WB P.125) Some isotopes are stable and do not change overtime.

This breakdown is called radioactive decay.

Name Characteristic Particle Emitted Nuclear Formula has mass and size has mass

electromagnetic radiation: 1. Radiowaves (how the radio works) 2.

13 2.7 Nuclear Decay (WB P.125) Some isotopes are stable and do not change overtime. Some isotopes are unstable and break down over time. This breakdown is called radioactive decay. The products of the break down are collectively called radiation. Name Characteristic Particle Emitted Nuclear Formula has mass and size has mass and size only has energy has mass and size has mass and size There are 7 types of electromagnetic radiation: 1. Radiowaves (how the radio works) 2. Microwaves (we heat food with this) 3. Infrared (remote controls) 4. Visible Light (we can see this one) 5. Ultraviolet (from the sun) 6. X Rays (to see our bones) 7. Gamma Rays 13 Gu 2016

14 2.8 Decay Equations (WB P ) Example: Complete the following radioactive decay equation.? +? + Mass Number = + Atomic Number = + Element: O He Example: Complete the following radioactive decay equation. As + Transmutation: When the parent element changes due to a gain or loss of a proton. Practice: Complete the following radioactive decay equation and determine whether transmutation has occurred. 1. Co + n 2. S + p 3. Os + e 14 Gu 2016

Alpha Decay () Beta Decay () Gamma Decay () Radiation: helium nucleus is lost Parent nucleus loses Ttotal mass lost = Transmutation occurs Radiation: is lost Parent nucleus: a neutron changes to, the

15 Alpha Decay () Beta Decay () Gamma Decay () Radiation: helium nucleus is lost Parent nucleus loses Ttotal mass lost = Transmutation occurs Radiation: is lost Parent nucleus: a neutron changes to, the electron is lost Transmutation occurs * symbolizes Radiation: Parent nucleus: loses No transmutation Practice: Complete the following alpha decay equations. 1. As + 2. Co + α 3. S + 4. Os + Practice: Complete the following beta decay equations. 1. Si + e 2. Co + e 3. Au+ 4. Nd + Practice: Complete the following beta decay equations. 1. Ga + 2. Nb + 15 Gu 2016

A large unstable isotope will decay many times until it becomes a stable daughter isotope. If we take all the decays that the parent isotope undergoes, we get a decay series. 1 What happened? 2 3 2.

16 A large unstable isotope will decay many times until it becomes a stable daughter isotope. If we take all the decays that the parent isotope undergoes, we get a decay series. 1 What happened? Properties of Radiation (WB P.128 #12) Different kinds of radiation have different abilities to penetrate. Decay Radiation Symbol Charge Mass What is it? Characteristics alpha decay alpha particle beta decay beta particle gamma decay gamma rays 16 Gu 2017

17 2.10 Half Life (WB P , 136) Radioactive decay occurs at a certain speed, or rate, for each kind of radioactive isotope. as a sample decays, the amount of radioactive isotopes that remain become less and less radioactive isotopes decay at a constant rate 1 st year 2 nd year 3 rd year 4 th year P P P P P P P P P P P P P P P P P P P P P: D: P P P P P P P P P P D D D D D D D D D D P: D: P P P P P D D D D D D D D D D D D D D D P: D: P P P D D D D D D D D D D D D D D D D D D P: D: Year Half life: the amount of time it takes for HALF of the nuclei in a sample of radioactive isotope to decay. Each half life means that 50% of the radioactive isotope has decayed. Example: Uranium 235 has a half life of 710 million years. Half Lives % Remaining Fraction Remaining How much is left after 4 half lives? 2. How much is left after 1420 million years? 17 Gu 2017

18 Example: Potassium 40 has a half life of 1.3 billion years Every 1.3 billion years, the amount of Potassium 40 decreases by 50% Time (billion years) # of Half lives Practice: 1. Element Q has a half life of 7 days. a) How many half lives have passed in 21 days? b) How many days have passed in 5 half lives? 2. Element X has a half life of 45 seconds. a) How many half lives have passed in 90 seconds? b) How much time has passed in 4 half lives? Practice: Fill in the chart. Number of Half Lives Time (years) % of Strontium 90 remaining Amount of Strontium g Gu 2017

19 Practice: Strontium 90 has a half life of 29 years. If you have 64g of strontium 90 today, how many grams will there be remaining after a) 29 years? b) 58 years? c) 4 half lives? Number of Half Lives Time (years) % of Strontium 90 Remaining Amount of Strontium Practice: Suppose a 128 g sample of a certain isotope has a half life of 1000 years. How many grams of the original sample is remaining after a) 1000 years b) 2000 years c) 3 half lives 19 Gu 2017

2.11 Decay Curves (WB P.135) A decay curve is a graph of the amount of parent isotope remaining versus time. What is the half life of the class? How many people are remaining after 2 half lives?

20 2.11 Decay Curves (WB P.135) A decay curve is a graph of the amount of parent isotope remaining versus time. What is the half life of the class? How many people are remaining after 2 half lives? Practice: Use the given decay curve for Californium 252 to answer the following questions. 1. What is the half life for Californium 252? 2. How long does it take for 80% of Californium 252 to decay? 3. How long does it take to only have 10% of the sample remaining? 4. How much sample is remaining after 3 half lives? 5. How many half lives have gone by after 20 years? 20 Gu 2017

21 2.12 Radioactive Dating (WB P.136) Scientists can use half lives to estimate the age of something. This is called radioactive dating. Scientist use the parent:daughter ratio in a sample to determined the age of a sample. % parent + % daughter = 100% Half Lives Parent Daughter P:D Example: You find a really old rock and do radioactive dating with isotope X, which has a half life of 7 years. Through a lot of chemical testing, you find that the rock has a 1:7 isotope X to daughter isotope ratio. How old is the rock? Example: A substance has a half life of 7 years. If the original mass of the parent isotope was 100g, how much time has passed if you measure 75g of the daughter isotope? 21 Gu 2017

22 Carbon dating is a common technique. is a radioactive isotope that can be used to date material that was once alive. Half life of carbon 14 = years. When an organism dies, the amount of carbon 14 in the organism starts to decrease as it radioactively decays. + Practice: You are using carbon 14 to determine the age of two bone fragments. If the original mass of the parent isotope was 200 g, how much time has passed if you measure 25 g of the remaining parent isotope for Fragment 1 and 50 g for Fragment 2? Fragment Fragment 1 Fragment 2 Mass Remaining Original Mass 200g 200g % remaining # Half lives 1 Half life 5730 years 5730 years Time 2.13 Nuclear Reactions (WB P.140) Nuclear reaction: reaction involving the modification of nuclei What happens to Chemical reactions Nuclear Reactions Atoms Atoms are to make new bonds No new elements Atoms are from one isotope to another Can make new elements Sub atomic particles only can be lost or gained,, electrons, and/or, can be lost or gained The Nucleus Energy Energy changes are relatively small. Energy changes are very large. Mass 22 Gu 2017

Practice: Complete the following nuclear equations and determine the bombarding particle. 1. + + 2. + + + 3 3. + + bombarding particle: bombarding particle: bombarding particle: 2.14 Fission (WB P.

23 Scientists can induce nuclear reactions by bombarding nuclei with radiation. Nuclear bombardment is when a large amount of radiation particles is sent into the nucleus to make it unstable in order to induce a nuclear reaction. Practice: Complete the following nuclear equations and determine the bombarding particle bombarding particle: bombarding particle: bombarding particle: 2.14 Fission (WB P ) Fission: when a large nucleus into two pieces of roughly equal mass, accompanied by a release of huge amounts of energy. Fission X N1 + N2 + neutrons + energy Some characteristics: a very small amount of mass is converted to energy the total mass of products is than total mass of reactants the total mass number stays the Because nuclear fission reactions are so high in energy, they were used to make nuclear weapons during wars. (WWII) 23 Gu 2017

Uranium naturally occurs in three isotopes: Isotope

Step 2 Uranium is created Instability Step 3 Uranium

nuclei, 2 3 neutrons + lots of energy Nuclear Reaction

(they are radioactive) and will undergo a decay series

24 Uranium naturally occurs in three isotopes: Isotope Abundance Stability U 238 > 99% stable U % stable U % stable U 235 will undergo fission if bombarded with a neutron. Bombardment Step 1 Fire at Uranium nucleus New Isotope Step 2 Uranium is created Instability Step 3 Uranium 236 is and splits apart Fission Step 4 Two daughter nuclei, 2 3 neutrons + lots of energy Nuclear Reaction Nuclear Reaction The two daughter nuclei are unstable (they are radioactive) and will undergo a decay series to a more stable isotope. Practice: Complete the following U 235 and U 236 fission nuclear equations Gu 2017

Critical mass: the amount of material needed to start a chain reaction. This uncontrolled reaction is the one that happens in nuclear bombs like the.

25 2.15 Nuclear Power Remember that a neutron is needed to start fission, and neutrons are also produced during fission. The neutrons produced can go on to start more fission. This results in a, where one reaction will start another reaction. Critical mass: the amount of material needed to start a chain reaction. This uncontrolled reaction is the one that happens in nuclear bombs like the. In nuclear reactors, there are control rods to absorb neutrons to prevent uncontrolled chain reactions. Nuclear reactors control chain reactions to safe levels so that the energy can be used to generate electricity. Canadian made nuclear reactors are called 25 Gu 2017

26 2.16 Fusion (WB P ) Fusion: the of two small nuclei to make a large nucleus, releasing a large amount of energy needs high and from a fission nuclear reaction to occur fusion in is what created all the elements on the periodic table there are no fusion nuclear plants there are fusion bombs called Fusion X1 + X2 N + radiaon + energy Example: Fusion in the Sun In the Sun, two hydrogen nuclei join under very high heat and pressure to form a helium nucleus. H + H + + energy Practice: Complete the following fusion nuclear reactions Gu 2017

27 2.17 Summary Fission vs. Fusion Fission Fusion Where? Starting Material Ending Material Type of reaction Amount of Energy Very large Larger than fission Nuclear Power Used in power plants like CANDU No fusion nuclear power Nuclear Weapons Example Equation Smaller Called Used in Hiroshima 1945 Much larger Called Never been used 27 Gu 2017

ICP Final Exam Review - Part 2

ICP Final Exam Review - Part 2 Modified True/False Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true. 1. A combustion reaction occurs