Toxins Unit Investigation II: Tracking Toxins Lesson 1: The Language of Change Lesson 2: Making...

Toxins Unit

Investigation II: Tracking ToxinsLesson 1: The Language of ChangeLesson 2: Making PredictionsLesson 3: Spare Change?Lesson 4: Scrub the AirLesson 5: Some Things Never ChangeLesson 6: Atom InventoryLesson 7: Toxins At Work

Toxins Unit – Investigation II

Lesson 1:

The Language of Change

Unit IV • Investigation II-X

© 2004 Key Curriculum Press.

ChemCatalyst Below is a chemical “sentence” describing the formation of a very toxic substance, hydrogen cyanide. NaCN (s) + HCl (aq) NaCl (aq) + HCN (g)

• What kinds of information does this chemical notation contain? List at least four pieces of information contained in this chemical notation.



The Big Question

• How do chemists describe chemical reactions, and what kinds of evidence do they look for to verify that their descriptions are correct?



You will be able to:

Identify the different components of a chemical equation and use that information to predict the outcome of the reaction it represents.



• The previous chemical “sentence” is called a chemical equation. A chemical equation describes change.

Notes

(cont.)



•The substances you start with before the change takes place are on the left side of the arrow. If there is more than one substance and they react with one another, they are called reactants.

•The substances you end up with after the change takes place are on the right side of the arrow. They are often referred to as products.

Notes (cont.)



Activity

Purpose: In this experiment, you will carry out the reaction between hydrochloric acid and sodium bicarbonate, and then do some analysis of the products that form.

(cont.)



Safety note: Hydrochloric acid is dangerous and causes burns. Do not get hydrochloric acid on your skin. In case of a spill, rinse with large amounts of water. Wear goggles.

(cont.)

(cont.)



Symbol What it Represents

Symbol What it Represents

HCl NaCl

(aq) H2O

+ (l)

NaHCO3 CO2

(g)

(cont.)

(cont.)



Observations

During Reaction

Observations

After Reaction

Observations

During Heating

Observations

After Heating

(cont.)



Making Sense

• Describe how a chemical equation keeps track of a chemical reaction.



HCl(aq) + NaHCO3(aq)

NaCl(aq) + H2O(l) + CO2(g)

Notes



Check-In

Consider the following reaction between sodium cyanide and a solution of hydrochloric acid.

NaCN (s) + HCl (aq) NaCl (aq) + HCN (g)

• Describe in detail what you would observe if you carried out this reaction.

• Describe the products that you would have.



Wrap-Up

• Chemical equations help chemists keep track of the substances involved in chemical and physical changes.

• Chemical equations indicate the reactants and products of chemical reactions.


Lesson 2:

Making Predictions



ChemCatalyst

Consider the following reaction:

AgNO3 (aq) + KCl (aq)

KNO3(aq) + AgCl(s)

• What do you expect to observe if you carried out the reaction?

• Translate the above chemical equation into writing, describing what is taking place.



The Big Question

• How do chemists predict the products of reactions and write the chemical reactions they represent?




Use chemical reactions to predict expected real-world observations and use real-world observations to write the chemical reaction they represent.



Activity

Purpose: This lesson provides you with practice translating chemical equations. You will have the opportunity to check you predictions by completing the laboratory procedure associated with each equation.

(cont.)



Safety note: Do not touch the dry ice with your fingers. It causes burns. NaOH, Ca(OH)2, and NH4OH are caustic. Do not get them on your skin. In case of a spill, rinse with large amounts of water. Wear goggles.

(cont.)

(cont.)



Reaction Prediction

s

Observation

s

Dry ice

1 CO2 (s) CO2 (g)

2 a) CO2 (s) CO2 (g)

b) CO2 (s) + H2O (l)

H2CO3 (aq)

3 CO2 (s) + Ca(OH)2 (aq)

CaCO3 (s) + H2O (aq)



Reaction Prediction

s

Observation

s

Calcium chloride

4 a) CaCl2 (s) CaCl2 (aq)

b) CaCl2(s)

Ca2+(aq) + 2 Cl– (aq)

5 CaCl2 (aq) + 2 NaOH (aq)

Ca(OH)2 (s) + 2 NaCl

(aq)

6 CaCl2 (s) + CuSO4 (s)

CaCl2 (s) + CuSO4 (s)



Reaction Prediction

s

Observation

s

Copper sulfate

7 a) CuSO4 (s) CuSO4 (aq)

b) CuSO4 (s)

Cu2+ (aq) + SO42–(aq)

8 CuSO4 (s) + 4 NH4OH (aq)

Cu(NH3)4SO4 (aq) +

4H2O (l)

9 CuSO4 (aq) + Zn (s)

Cu (s) + ZnSO4

(aq)



Making Sense

• Make a list of all the different types of things that you observed today that are associated with changes in matter.



Check-In

• No Check-In exercise.



Wrap-Up

• Chemical equations allow chemists to predict and track changes in matter.


Lesson 3:

Spare Change?



ChemCatalyst

The following two equations both describe what happens when dry ice is placed in water:

CO2 (s) CO2 (g)

CO2 (s) + H2O (l) H2CO3 (aq)

• What differences do you see in these two equations?

• Why do you think two equations are needed to describe what happens?



The Big Question

• What are the differences between physical changes and chemical changes?




Convert back and forth between chemical reaction notation and real world observations, and identify each change as either chemical or physical.



• In a chemical equation describing a physical change, the chemical formulas do not change in going from reactants to products. However, the phase (s, l, & aq) does change.

• In a chemical equation describing a chemical change, the chemical formulas of the reactants are different from those of the products.

Notes



Activity

Purpose: This activity provides you with practice distinguishing between physical and chemical changes using only the chemical equations.



Making Sense

• Compare your observations for each reaction to the chemical equations. If you were asked to classify a reaction as a physical or chemical change, which would you prefer to have, a set of observations or chemical equations? Explain your thinking.



CaCl2 (s) CaCl2 (aq)

CaCl2(s) Ca2+(aq) + 2 Cl– (aq)

Notes



Check-In

• Does the following chemical equation describe a physical change or a chemical change? Explain how you can tell.

C17H17O3N(s) + 2C4H6O3(l)

C21H21O5N(s) + 2 C2H4O2(l)



Wrap-Up

• Chemical changes involve the formation of new substances. Physical changes, such as phase changes, involve a change in form.

• Chemical equations often provide more straightforward information about the type of change than mere observations.


Lesson 4:

Scrub the Air



ChemCatalyst

In enclosed spaces such as on a space station or in a submarine, the breathing of the occupants causes a natural build up of carbon dioxide, CO2. Too much CO2 in the air is highly toxic.

• List two ways to use chemical change to eliminate CO2 (g).



The Big Question

• How does molecular bonding affect the outcome of chemical reactions?




Classify certain chemical reactions as either combination or decomposition and predict the possible products when given specific reactants.



• In a decomposition reaction, one reactant is broken apart into two or more substances. In a combination reaction, two or more substances combine to form a single product.

AB A + B (decomposition)

A + B AB (combination)

Notes

(cont.)



CaCO3 CaO +

(cont.)



Activity

Purpose: You will compare different kinds of chemical reactions and learn the notation used to write chemical reactions.



Making Sense

• Explain how you can predict the products of the decomposition of NaCl.

• Explain how you can predict the product of the combination of carbon and hydrogen.



Check-In

• List a possible product of the following combination reaction:

CH4 (g) + O2 (g)



Wrap-Up

• The substances in chemical reactions obey the bonding rules we have learned for ionic and covalent substances.

• A decomposition reaction in one in which one reactant is broken apart into two or more substances.

• A combination reaction is one in which two or more substances combine to form a single product.


Lesson 5:

Some Things Never Change



ChemCatalyst

Consider the following reaction.

Na2CO3 (aq) + CaCl2 (aq)

NaCl (aq) + CaCO3 (s)

• Describe what you will observe when Na2CO3 (aq) and CaCl2 (aq) are mixed.

• Will the mass increase, decrease, or stay the same after mixing? Explain.



The Big Question

• What is the relationship between the mass of reactants and the mass of products of a chemical reaction?




Explain the relationship between the mass of reactants and the mass of products of a chemical reaction.



Activity

Purpose: In this activity, you will explore conservation of matter and how it applies to the world around you.

(cont.)



Weight before mixing

Predict the weight after

mixing

Observations after mixing

Weight after

mixing

Na2CO3 (aq) + CaCl2 (aq)

Na2CO3 (aq) + C2H4O2 (aq)

(cont.)

(cont.)



Chemical Reaction 1:

?

>

=

< ?

Reactants Products

(cont.)

(cont.)



Chemical Reaction 2:

>

=

< ? ?

Reactants Products

(cont.)



Making Sense

• In your own words, explain what happens to matter and its mass when a chemical reaction or physical change occurs.



• Law of conservation of matter:

Matter can be neither created nor destroyed in chemical reactions. This means that in chemical reactions and physical changes atoms do not come in and out of existence. They are simply rearranged. Since atoms have mass, the mass does not change.

Notes



Check-In

Consider the following reaction:

CuCO3 (s) + H2SO4 (aq)

CO2 (g) + CuSO4 (aq) + H2O (l)

• Describe what you will observe when CuCO3 (s) and H2SO4 (aq) are mixed.

• Will the mass increase, decrease, or stay the same after mixing? Explain.

• Will the weight increase, decrease, or stay the same after mixing? Explain.



Wrap-Up

• Individual atoms are conserved in chemical reactions and physical changes: the number of atoms of each element remains constant from start to finish.

• Matter is conserved in chemical reactions: the total mass of the products equals the total mass of the reactants.

• Gases have mass.


Lesson 6:

Atom Inventory



ChemCatalyst

• Does the following equation obey the law of conservation of matter? Why or why not?

CuCl2(aq) + Na2S (aq)

CuS (s) + NaCl (aq)



The Big Question

• What does it mean to “balance” a chemical equation?




Use the concept of a balanced chemical equation to account for the atoms involved in a chemical reaction.



• The subscripts in a chemical equation indicate how many atoms are in the chemical formula for that substance.

• The large numbers in front of chemical formulas are called coefficients. They indicate how many parts of that substance there are in a reaction.

Notes



Activity

Purpose: In this activity, you will practice balancing chemical reactions.

(cont.)



The four unbalanced reactions are given below:

1. Zn(s) + HCl(aq) ZnCl2(aq) + H2(g)

2. O2(g) + H2(g) H2O(l)

3. O2(g) + CH4(g) CO2 + H2O(l)

4. NO2 + H2O(l) HNO3(aq) + NO(g)

(cont.)



Making Sense

The balanced equations are shown below, with the new coefficients highlighted in bold.

1. Zn (s) + 2 HCl (aq) ZnCl2 (aq) + H2 (g)

2. O2 (g) + 2 H2 (g) H2O (l)

3. 2 O2 (g) + CH4 (g) CO2 (g) + 2 H2O (l)

4. 3 NO2 (g) + H2O (l) 2 HNO3 (aq) + NO (g)

(cont.)



C2H6 + 4 O2 2 CO2 + 3 H2O

(cont.)

(cont.)



Example #1: Balance the following equation

NO (g) + O2 (g) NO2 (g)

(cont.)

(cont.)



Example #2: Balance the following equation for rusting iron.

Fe (s) + O2 (g) Fe2O3 (s)

(cont.)



Check-In

• Balance the following equation.

Ca + O2 CaO



Wrap-Up

• In order to conserve matter, the number of atoms on both sides of a chemical equation must be equal.

• When an equation is balanced it tells you how many molecules or moles of each substance take part in a reaction and how many molecules or moles of product (s) are produced.


Lesson 7:

Toxins At Work



ChemCatalyst

Hemoglobin (Hb) is the molecule in your blood that carries oxygen throughout your body. Ca3(PO4)2 (s), calcium phosphate, is the main compound in bones and teeth.

(cont.)



Below are two reactions that might take place in your body, one involving carbon monoxide, CO, and the other involving lead chloride, PbCl2.

O2–Hb (aq) + CO (g) CO–Hb (aq) + O2 (g)

Ca3(PO4)2 (s) + Pb(NO3)2 (aq) Pb3(PO4)2(OH) (s) + Ca(NO3)2 (aq)

• Which atoms rearranged in each case?

• Why are CO and PbCl2 toxic?

(cont.)



The Big Question

• How do toxins act upon our bodies?




Recognize single displacement and double displacement reactions and predict the possible products when given specific reactants.



Single displacement: A single displacement reaction begins with an element and a compound. The compound breaks apart and then one piece combines with the element while the other piece is left in the elemental form. The general reaction can be written as AB + C AC + B, where C displaces B.

Notes

(cont.)



Double displacement: A double displacement reaction begins with two compounds that break apart. Their parts then recombine into two new products. The general reaction can be written as AB + CD AD + CB, where B and D exchange with one another (or A and C exchange with one another).

(cont.)

Notes (cont.)



• Groups of atoms are called polyatomic ions.

• The atom or groups of atoms that move around in chemical reactions are called species.

(cont.)

Notes (cont.)



Single displacement reactions:

Cl2 + CaI2 [CaCl2 + I2]

Note that the products [Ca + 2ClI] are not produced.

Mg + 2HCl [H2 + MgCl2]

Note that the products [Cl2 + MgH2] are not produced.

(cont.)

Notes (cont.)



Double displacement reactions:

CsF + NaOH [CsOH + NaF]

Note that the products [CsNa + FOH] are not produced.

PbI2 + 2K2S [PbS + 2KI]

Note that the products [K2Pb + SI2] are not produced.

Notes (cont.)



Activity

Purpose: In this worksheet, you will practice predicting the products of displacement reactions.



Making Sense

• Explain in a step-by-step fashion how you completed the above equations.

• Suppose you drank a solution containing the toxin PbI2. Suggest how this toxin may act in your body.



• Combination: A + B AB

• Decomposition: AB A + B

• Single displacement: AB + C AC + B

• Double displacement: AB + CD AD + BC

Notes



Check-In

Thallium is the 81st element on the periodic table. Not that long ago, thallium compounds were used both as rat poison and in hair removal products. However, these compounds are quite toxic to humans and hair loss is one of the first signs of thallium poisoning. Predict the products of the following reaction and balance the equation.

TlCl3 + LiOH



Wrap-Up

• Many chemical reactions can be classified as displacement reactions, in which one part of a compound is exchanged by another.

• Toxins act by displacing pieces of compounds in your body.

Toxins Unit Investigation II: Tracking Toxins Lesson 1: The Language of Change Lesson 2: Making...

Documents

Transcript of Toxins Unit Investigation II: Tracking Toxins Lesson 1: The Language of Change Lesson 2: Making...