chem com unit 1b a look at water and its contaminants
TRANSCRIPT
A Look at Water and its A Look at Water and its ContaminantsContaminants
Unit 1 Section BUnit 1 Section B
ChemCom Hon IChemCom Hon I
Ms. Brandi ThomasMs. Brandi Thomas
**B.1 Physical Properties of Water**B.1 Physical Properties of Water
Properties that can be observed and measured Properties that can be observed and measured without changing the chemical makeup of without changing the chemical makeup of substancesubstance
This section focuses on the physical properties This section focuses on the physical properties of water – of water – density, density, physical state, physical state, surface tension, surface tension, boiling and freezing points boiling and freezing points and the solvent characteristicsand the solvent characteristics
Aqueous SolutionsAqueous Solutions Water based solutionsWater based solutions
** Mixtures and Solutions** Mixtures and Solutions
MixtureMixture Two or more substances that retain there individual Two or more substances that retain there individual
propertiesproperties Heterogeneous MixtureHeterogeneous Mixture
Composition is not the same or uniform throughout.Composition is not the same or uniform throughout.• SuspensionSuspension
Particles are large enough to settle out and can be filteredParticles are large enough to settle out and can be filtered
• ColloidColloid Particles are smaller than in suspension can not settle out…Particles are smaller than in suspension can not settle out…
cloudy appearancecloudy appearance
• DissolvesDissolves Particles smaller than particles in colloids and separate into Particles smaller than particles in colloids and separate into
particles so small they can not be seen.particles so small they can not be seen.
** Mixtures and Solutions** Mixtures and Solutions
Homogeneous MixtureHomogeneous Mixture A mixture that is uniform throughout A mixture that is uniform throughout
• Solutions are homogeneous Solutions are homogeneous • SoluteSolute
The dissolved substanceThe dissolved substance
• SolventSolvent The dissolving agentThe dissolving agent
**Molecular view of Water**Molecular view of Water AtomAtom
All matter is composed of atomsAll matter is composed of atoms ElementElement
Matter made up of only one type of atomMatter made up of only one type of atom 90 different elements found in nature90 different elements found in nature
CompoundCompound A substance with two or more elements linked together chemically in A substance with two or more elements linked together chemically in
fixed positionsfixed positions Pure substancePure substance
Each element and compound. A uniform and definite composition and Each element and compound. A uniform and definite composition and distinct propertiesdistinct properties
MoleculeMolecule• Smallest unit of a pure substance that retains propertiesSmallest unit of a pure substance that retains properties
Chemical BondChemical Bond• ““glue” that holds atoms of a molecule together.glue” that holds atoms of a molecule together.
**B.4 Symbols, formulas, and **B.4 Symbols, formulas, and EquationsEquations
An introduction to symbols, formulas, and An introduction to symbols, formulas, and equations and to the significance of equations and to the significance of subscripts and coefficients.subscripts and coefficients. International “chemical language” to International “chemical language” to
represent atoms, elements, and compounds.represent atoms, elements, and compounds. Chemical Symbols = “letters” of chemical Chemical Symbols = “letters” of chemical
lang.lang.• Each element is assigned a chemical symbol.Each element is assigned a chemical symbol.• Only first letter is capitalizedOnly first letter is capitalized
**B.4 Symbols, formulas, and **B.4 Symbols, formulas, and EquationsEquations
All elements are organized into the All elements are organized into the periodic table.periodic table.
Chemical formula = “the word” in chemical Chemical formula = “the word” in chemical lang.lang. Ex:HEx:H22O = WaterO = Water A subscript indicates how many atoms of A subscript indicates how many atoms of
each element are in the molecule or unit of each element are in the molecule or unit of substancesubstance
Ex:CEx:C33HH8 = 8 = Propane (3 Carbon molecules and 8 Propane (3 Carbon molecules and 8 Hydrogen)Hydrogen)
**B.4 Symbols, formulas, and **B.4 Symbols, formulas, and EquationsEquations
Chemical equations = the “sentences” of Chemical equations = the “sentences” of chemical lang.chemical lang. Each chemical equation represents a Each chemical equation represents a
chemical reaction that happens or that chemical reaction that happens or that someone predicts might happen.someone predicts might happen.
Chemical Reactions = breaking and the Chemical Reactions = breaking and the forming of chemical bonds, causing atoms forming of chemical bonds, causing atoms to rearrange into new substances.to rearrange into new substances.
**B.4 Symbols, formulas, and **B.4 Symbols, formulas, and EquationsEquations
Reactants = the original substances in a Reactants = the original substances in a chemical equation.chemical equation.
Products = the new substance formed Products = the new substance formed from the rearrangement of the reactantfrom the rearrangement of the reactant
**B.4 Symbols, formulas, and **B.4 Symbols, formulas, and EquationsEquations
Diatomic MoleculesDiatomic Molecules They exists as two They exists as two
bonded atoms of the bonded atoms of the same element.same element.
Gen-U-ine Diatomic Gen-U-ine Diatomic moleculesmolecules
Elements that exits as Elements that exits as Diatomic MoleculesDiatomic Molecules
ElementElement FormulaFormula
HydrogenHydrogen HH22
NitrogenNitrogen NN22
OxygenOxygen OO22
FluorineFluorine FF22
ChlorineChlorine ClCl22
BromineBromine BrBr22
IodineIodine II22
**B.5 The Electrical Nature of **B.5 The Electrical Nature of MatterMatter
The Electrical nature of matter is The Electrical nature of matter is discussed in terms of interaction among discussed in terms of interaction among charges, and in terms of neutrons, charges, and in terms of neutrons, protons, and electrons.protons, and electrons. Water is described as a polar moleculeWater is described as a polar molecule Like forces repel each otherLike forces repel each other Unlike charges attract each other.Unlike charges attract each other.
**B.5 The Electrical Nature of **B.5 The Electrical Nature of MatterMatter
Neutral atoms have equal numbers of Neutral atoms have equal numbers of positively charged particles called Protons positively charged particles called Protons and negatively charge electrons. Neutrons and negatively charge electrons. Neutrons are electrically neutral atomsare electrically neutral atoms
Protons = (+)Protons = (+) Electrons = (-)Electrons = (-) Positive neutrons and negative elections Positive neutrons and negative elections
form the glue that holds atoms together.form the glue that holds atoms together.
**B.6 Ions and Ionic Compounds**B.6 Ions and Ionic Compounds
Molecules make one type of compoundMolecules make one type of compound Another type of compound = ionsAnother type of compound = ions Ions are charged atoms. Atoms can gain or Ions are charged atoms. Atoms can gain or
lose electrons to form positive or negative lose electrons to form positive or negative ions.ions.
Ionic compounds are composed of both Ionic compounds are composed of both positive and negative ions. (no net charge)positive and negative ions. (no net charge)• When an cation sticks to an anion = ionic When an cation sticks to an anion = ionic
compoundscompounds
**B.6 Ions and Ionic Compounds**B.6 Ions and Ionic Compounds
AnionsAnions When and atom gains one or more electronWhen and atom gains one or more electron Resulting in an negative chargeResulting in an negative charge
CationsCations An atom losing one or more election resulting An atom losing one or more election resulting
in a positive charge.in a positive charge. Polyatomic (many atom) ionPolyatomic (many atom) ion
An ion consisting of a group of bonded atomsAn ion consisting of a group of bonded atoms Figure 18 (page 33)Figure 18 (page 33)
***Figuring out how many electrons ***Figuring out how many electrons atoms gain or lose…atoms gain or lose…
Count forward from it on the periodic table until Count forward from it on the periodic table until you reach the next noble gasyou reach the next noble gas
Count backward from it on the periodic table Count backward from it on the periodic table until you reach the last noble gas.until you reach the last noble gas.
If the forward < than backward, the element will If the forward < than backward, the element will gain elections (amount you counted) for a gain elections (amount you counted) for a negative chargenegative charge
If backward is < than forward then you will lose If backward is < than forward then you will lose the number of electrons that you counted.the number of electrons that you counted.
Important: SKIP OVER TRANSITION METALS Important: SKIP OVER TRANSITION METALS WHEN COUNTNG TO NOBLE GASES,WHEN COUNTNG TO NOBLE GASES,
Practice ProblemPractice Problem
What will the charges of the following What will the charges of the following elements be when they gain or lose elements be when they gain or lose electrons to gain the same electron electrons to gain the same electron figuration as the nearest noble gas?figuration as the nearest noble gas?
A) Magnesium (Mg)A) Magnesium (Mg) B) Calcium (Ca)B) Calcium (Ca) C) Bromine (Br)C) Bromine (Br)
~Properties of Ionic Compounds~Properties of Ionic Compounds
Ionic compounds form CrystalsIonic compounds form Crystals Ionic compounds often have high melting Ionic compounds often have high melting
and boiling pointsand boiling points Ionic compounds are hard and brittleIonic compounds are hard and brittle Ionic compounds conduct electricity when Ionic compounds conduct electricity when
dissolved in water or melteddissolved in water or melted
~Writing Ionic Names from ~Writing Ionic Names from FormulasFormulas
Step 1Step 1 Determine the base nameDetermine the base name
• The first word is the cationThe first word is the cation• The second word is the anion (if polyatomic ion The second word is the anion (if polyatomic ion
just look up on polyatomic chart)just look up on polyatomic chart)
Step 2Step 2 Determine whether or not the compound will Determine whether or not the compound will
require a roman numeralrequire a roman numeral Step 3Step 3
***Writing Ionic Formulas from ***Writing Ionic Formulas from namesnames
Step 1Step 1 From the base name, determine the formula From the base name, determine the formula
and charge of ionsand charge of ions Step 2Step 2
Write the formulas of the cations and anions Write the formulas of the cations and anions next to each other.next to each other.
Step 3Step 3 Devise an ionic formula that gives the Devise an ionic formula that gives the
compound a neutral charge.compound a neutral charge.
Writing Ionic Formulas from Names Writing Ionic Formulas from Names Example “Beryllium Hydroxide”Example “Beryllium Hydroxide”
1.1. ““Beryllium” indicates BeBeryllium” indicates Be+2+2 and and “hydroxide” indicates OH“hydroxide” indicates OH-1-1
2.2. Putting them together we get BePutting them together we get Be+2+2OHOH-1-1..
3.3. Because Beryllium hydroxide has to be Because Beryllium hydroxide has to be electrically neutral, there needs to be two electrically neutral, there needs to be two hydroxide ions for each beryllium ion. hydroxide ions for each beryllium ion. As a result the formula of beryllium As a result the formula of beryllium hydroxide is Be(OH)hydroxide is Be(OH)22
Write the formula of the following Write the formula of the following ionic Compoundionic Compound
A) Lithium acetateA) Lithium acetate B) sodium nitrateB) sodium nitrate
Write the formula of the following Write the formula of the following ionic Compoundionic Compound
A) Lithium acetateA) Lithium acetate LiCLiC22HH33OO22
B) sodium nitrateB) sodium nitrate NaNONaNO33
Group ActivityGroup Activity
In Groups of 4 do building skills on page In Groups of 4 do building skills on page 34.34.
B.7 Water testingB.7 Water testing
Purpose: allow you to use a method that Purpose: allow you to use a method that chemist, including those investing the chemist, including those investing the Riverwood fish kill , use to detect specific Riverwood fish kill , use to detect specific ions in water solutionsions in water solutions
Confirming test: A positive test confirms Confirming test: A positive test confirms the ion in question is present.the ion in question is present. Change in color or appearance of precipitate Change in color or appearance of precipitate
indicate a positive test.indicate a positive test.
B.7 Water testingB.7 Water testing
A negative test does not equal an absent A negative test does not equal an absent ion.ion.
Qualitative test vs. Quantitative test. (This Qualitative test vs. Quantitative test. (This lab is qualitative…(only test for presence lab is qualitative…(only test for presence not amount)not amount) Testing for Testing for
• Iron (III) (FeIron (III) (Fe+3+3))• Calcium (Ca Calcium (Ca 2+2+ ) )• Chloride (ClChloride (Cl--))• Sulfate (SOSulfate (SO44
2-2-))
B.7 Water testingB.7 Water testing
Reference SolutionsReference Solutions Contains the ions of interestContains the ions of interest
ControlControl Does not contain the ion of interestDoes not contain the ion of interest
The other samples The other samples Natural Water/Mystery WaterNatural Water/Mystery Water Tap waterTap water
• Are to be compared to the reference solutionsAre to be compared to the reference solutions• Lab video
B.7 Water testingB.7 Water testing
Post LabPost Lab Questions 1-4 page 38Questions 1-4 page 38 For the next 5 min:For the next 5 min:
• With your partner go over questions 1-4 With your partner go over questions 1-4
B.8 Pure and Impure WaterB.8 Pure and Impure Water
Most families in the US have clean water Most families in the US have clean water but not pure water.but not pure water. Pure is almost impossible since so many Pure is almost impossible since so many
substances dissolve in water, (even substances dissolve in water, (even atmospheric gases like nitrogen, hydrogen, atmospheric gases like nitrogen, hydrogen, and carbon dioxide.and carbon dioxide.
B.9 The RiverWood MysteryB.9 The RiverWood Mystery
Making Decisions Group activityMaking Decisions Group activity In groups of 4 read over the directions and In groups of 4 read over the directions and
questions on page 38-39 and answer questions on page 38-39 and answer questions. questions.
Put the answers in your notes section of class Put the answers in your notes section of class binder.binder.
We will come back to these for a group We will come back to these for a group discussion and for our town council meetingdiscussion and for our town council meeting
B.10 What are the possibilitiesB.10 What are the possibilities
Bridge to part CBridge to part C Identifies the processes just used by Identifies the processes just used by
students as typical work of scientist.students as typical work of scientist. Now that we know about the types of Now that we know about the types of
substances that can be dissolved or substances that can be dissolved or suspended in water, we can determine which suspended in water, we can determine which ones are potentially harmful to aquatic life.ones are potentially harmful to aquatic life.