Toxins Unit

Toxins Unit

Investigation I: Dissolving ToxinsLesson 1: Lethal DoseLesson 2: Bearly AliveLesson 3: Mixing It Up!Lesson 4: Weighing InLesson 5: Finding SolutionsLesson 6: Holey MoleyLesson 7: Is It Toxic?

Toxins Unit – Investigation I

Lesson 1:

Lethal Dose

Unit IV • Investigation I-X

© 2004 Key Curriculum Press.

ChemCatalyst

• Which substance do you think is most toxic to you – alcohol (ethanol, C2H6O), aspirin (salicylic acid, C7H6O3), or arsenic (As)? Explain your thinking.

• How do you think toxicity is determined?



The Big Question

• How is the toxicity of a substance measured and described?



You will be able to:

Calculate the toxicity of substances based on the lethal dose.



• Lethal dose (LD50) is the amount of an ingested substance that kills 50 percent of a test sample. It is expressed in mg/kg, or milligrams of substance per kilogram of body weight.

Notes



Activity

Purpose: In this activity you will compare the toxicity of various substances.



Making Sense

• How is dosage related to toxicity?



Check-InMethadone is a medication used as a painkiller and as a treatment for those recovering from heroin addiction. The LD50 for methadone is 95 mg/kg.

• Would you consider methadone to be more or less toxic than acetaminophen (LD50 = 2404 mg/kg) or aspirin (LD50 = 200 mg/kg)?

• Explain how you would calculate the amount of this substance that would be lethal to a 120-pound human.



Wrap-Up

• Toxicity is relative to dosage: The toxicity (or therapeutic effect) of a substance depends on the dose in which it is received.

• The lethal dose (or therapeutic dose) of a substance is often expressed as a ratio between a certain mass of the substance and one kilogram of the body weight of an organism exposed to the substance.


Lesson 2:

Bearly Alive



ChemCatalyst

• Drinking water in our homes contains low concentrations of dissolved chlorine, a highly toxic substance. Why can we drink the water?

• What do you think concentration means?



The Big Question

• What are the components of solutions, and how are the concentrations of solutions described?




Identify the components of solutions and explain their relationship to the concept of solution concentration.



• A solution is a mixture of two or more substances that is uniform throughout. The substance in the greatest amount is called the solvent. The solute is dissolved in the solvent.

• Concentration is the amount of solute for a specified amount of solvent. A common measure of concentration is moles per L, moles/L, which is referred to as molarity, M.

Notes



Activity

Purpose: This activity introduces you to

solution chemistry and allows you to

examine solutions of differing

concentrations.

(cont.)



Solution Solute Observations Rank the bear size from 1-8

Water —

0.1 M sugar C12H22O11



Corn syrup C12H22O11

0.1 M salt NaCl

0.5 M salt NaCl

1.0 M salt NaCl



Making Sense

What do you think is happening in this activity? Write a paragraph explaining your ideas. Include your answers to the following questions:

• What causes the size of the gummy bears to change?

• Why are the gummy bears in the sugar solutions ranked the way they are?

(cont.)



• Why are the gummy bears in the salt solutions different sizes than the gummy bears in the sugar solutions of the same concentration?

(cont.)

(cont.)



• The movement of substances from an

area of high concentration to an area of lower concentration is called diffusion.

(cont.)



Check-In

• What would happen if you placed a gummy bear in a 1.5 M sugar solution overnight? Use your data table to help you determine the outcome. Draw a picture showing which molecules are moving. Explain your answer in terms of diffusion of water into or out of the bear.



Wrap-Up• A solution is a mixture that is uniform

throughout. The substance in the greatest amount is the solvent. The substance that is dissolved is the solute.

• Molarity tells us how many particles or molecules are in solution. Molarity is a measure of the concentration of a solution.

(cont.)



• Diffusion is defined as the movement of molecules from an area of higher concentration of that molecule to an area of lower concentration of that molecule.

• Salts dissolve in water to give two (or more) ions. Molecular substances do not dissociate; they remain intact as individual molecules.

(cont.)


Lesson 3:

Mixing It Up!



ChemCatalyst

• List three things that dissolve in water.

• List three things that do not dissolve in water.



The Big Question

• What is solubility, and how is it determined?




Explain the concept of solubility and determine the solubility of a substance.



• Homogeneous: A mixture in which the

substances are distributed uniformly.

All solutions are homogeneous by

definition.

• Heterogeneous: A mixture that is not

uniform throughout.

Notes



Activity

Purpose: In this activity you will examine the solubility of five solutes in water.

(cont.)



Test tube

Solute after Step 1 after Step 2

#1 ethanol C2H6O (l)

#2 butanol C4H10O (l)

#3 oil C20H42 (l)

#4 copper sulfate CuSO4 (s)

#5 carbon dioxide

CO2 (g)



Dye molecules

View 1: Uniform distribution of

molecules

View 2: More molecules at

the bottom

(cont.)



Making Sense

• Explain how you can tell when a substance is soluble or insoluble in water.



• A solute is a gas, liquid, or solid that dissolves when mixed with another substance.

• A solvent is the substance present in the greatest quantity in a solution. Solvents are usually liquids.

Notes

(cont.)



• Soluble substances are solutes that dissolve completely.

• Insoluble substances are those that do not dissolve at all.

• Partially soluble substances are those for which only a certain amount will dissolve. Many substances are partially soluble.

(cont.)



Check-In

• There is solid sugar at the bottom of your tea. Why do the last sips taste sweeter?

• All of the sugar in your tea is dissolved. The last sips taste the same as the first. Use a molecular view of sugar dissolved in water to explain why.



Wrap-Up

• Gases, liquids, and solids can dissolve in water. However, some substances are not soluble.

• Partially soluble means that when two substances are mixed, a solution forms but one substance is leftover.

• Solutions are homogeneous. The molecules or ions of the solute are distributed uniformly between the solvent molecules.


Lesson 4:

Weighing In



ChemCatalyst

• Which do you think is more toxic—one mole of arsenic, As, or ten grams of arsenic? Explain your reasoning.



The Big Question

• How is the mole concept used to connect the mass of a sample to the number of particles it contains?




Use the molar mass of a substance to find the number of molecules in a sample.



Activity

Purpose: The purpose of today's lesson is to explore the relationship between mass and moles.

(cont.)



Rice Lentils

Volume of each

Mass of the baggie

Mass of ten pieces

Mass of one piece (calculated)

# of pieces (calculated)

# of pieces (counted)

(cont.)

(cont.)



substance # of particles # of moles measured mass

He (g) 6.02 1023 1 mole

He (g) 1.204 1024 2 moles 8.0 g

Al (s) 1 mole 27.0 g

Cu (s) 6.02 1023 1 mole

As (s) 6.02 1023 1 mole

NaCl (s) 6.02 1023 1 mole

MgF2 (s) 31.2 g

MgF2 (s) 6.02 1023 1 mole 62.3 g

H2O (l) 3.01 1023

H2O (l) 6.02 1023 1 mole

C6H12O6 6.02 1023 1 mole

(cont.)



Making Sense

• How is measuring the mass of a substance the same as counting?



• The molar mass of a substance is how much one mole of that substance weighs. Molar mass is the sum of all of the atomic masses (in grams) in a chemical formula.

Notes

(cont.)



molar mass in grams/mole

add the atomic weights of the atoms in the chemical

formulamass in gramsweight of the substance

moles6.02 1023 (Avogadro’s number) of each of the atoms in the chemical

formula

(cont.)



Check-In

• You have one mole of NaCl and one mole of KCl. Which one weighs more? Explain your thinking.



Wrap-Up

• The atomic weight on the periodic table is equivalent to the mass of 1 mole of atoms of the element in grams.

• The molar mass of a compound is the sum of the atomic weights of the atoms in the compound.

• Molar mass allows you to convert between moles and grams.


Lesson 5:

Finding Solutions



ChemCatalyst

Consider the following solutions:

1.0 L

1.0 M C6H12O6

(glucose)

500 mL

1.0 M C12H22O11

(sucrose)

1.0 L

1.0 M C12H22O11

(sucrose)

(cont.)



• Which solution has the most molecules? Explain.

• Which solution has the greatest concentration? Explain.

• Which solution weighs the most? Explain.

(cont.)



The Big Question

• What are the methods that can be used to produce a solution of a specific concentration?




Produce a solution of specific concentration by using the mass of solute and its molar mass or by using dilution.



Activity

Purpose: You will prepare four solutions by two different methods.

Volume conversion: 1 L = 1000 mL

(cont.)



mass moles volume molarity

342 g 1.0 mole 1.0 L 1.0 M

34.2 g 1.0 L 0.10 M

3.42 g 0.010 moles 100 mL

0.342 g 0.010 M

(cont.)

(cont.)



volume molarity moles dilute to

new molarity

100 mL 1.0 M 0.10 moles 1.0 L 0.10 M

100 mL 0.10 M 0.010 moles 1.0 L

10 mL 0.10 M 0.0010 moles

100 mL

10 mL 0.010 M 100 mL

(cont.)

(cont.)



Method of preparation

Concentration

Color

Solution A

weighed 3.42 g sugar, diluted

to 100 mL

0.10 M dark red

Solution B

Solution C

Solution D

(cont.)



Making Sense

• Describe two ways to make a 0.010 M sugar solution.



Check-In

• How many moles of sucrose does 100 mL of a 0.10 M sucrose solution contain?

• How many moles of sucrose does 25 mL of a 0.10 M sucrose solution contain?



Wrap-Up

• When concentration is expressed in moles of solute per liter of solution it is referred to as molarity.

• Solutions of specific concentrations can be created by weighing out the solute or by dilution of an existing solution of known concentration.


Lesson 6:

Holey Moley



ChemCatalyst

How would you calculate the total amount of glucose, in grams, in the blood of an average human?

Useful information:

• Blood volume = 5.5 L

• Glucose concentration = 0.0056 M

• Molar mass of glucose (C6H12O6) = 180 g/mol



The Big Question

• What is the connection between the mass of a solute, its molar mass, and the concentration of solution it is in?




Convert between the mass of solute in solution, its concentration, and its molar mass.



Proportional analysis

Step 1: Convert liters to moles using the concentration.

x = 0.031 moles glucose

€

0.0056 moles glucose1 L blood

=x moles glucose

5.5 L blood

Notes

(cont.)



Step 2: Convert moles to grams using the molar mass

y = 5.5 g glucose

€

180 g glucose1 mole glucose

=y g glucose

0.031 moles glucose

Notes (cont.)

(cont.)



Dimensional analysis

€

5.5 L blood• 0.0056 moles1 L blood

•180 g glucose1 mole glucose

=5.5 g glucose

Notes (cont.)



Activity

Purpose: You will practice solving problems in which you convert between mass of solute, moles of solute, and liters of solution using molecular weight and molarity.

(cont.)



mass moles volume molarity

342 g 1.0 mole 1.0 L

34.2 g 1.0 L 0.10 M

3.42 g 100 mL

0.342 g 0.10 M

27.4 g 0.080 moles 1.0 L 0.080 M

17.1 g 1.0 L 0.050 M

6.84 g 1.0 L

27.4 g 0.080 moles 500 mL 0.040 M

17.1 g 0.050 moles 0.025 M

500 mL 0.010 M



0.1 M sucrose 0.01 M sucrose0.05 M sucrose

(cont.)

(cont.)



volume molarity moles dilute to new molarity

1.0 L 1.0 M 1.0 moles 10.0 L 0.10 M

1.0 L 0.10 M 10.0 L

500 mL 1.0 M 1.0 L

250 mL 1.0 M 1.0 L

500 mL 0.10 M 1.0 L

250 mL 0.10 M 1.0 L

500 mL 0.20 M 5.0 L

250 mL 0.20 M 5.0 L



Making Sense

• Explain how to make a glucose solution that has the same concentration as blood.

• Explain how to dilute a 1.0 M glucose solution so that it has the same concentration as human blood.

(cont.)



Sample Problem #1 – Calculating molarity of a solution:

• What is the molarity of 5.5 L of blood containing 10 grams of glucose?

(cont.)

(cont.)

Sample Problems Involving Molarity



Sample Problem #2 – Calculating grams of solute needed for a specific molarity.

• How many grams of glucose, C6H12O6, would you need to create 250 mL of solution with a molarity of 0.0050 moles / liter?

(cont.)

(cont.)



• When a solution is diluted, solvent is added without the addition of more solute. Since the amount of solute is not changed, our calculations reflect this fact.

# of moles before dilution = # of moles after dilution

• Since the moles of solute is equal to the molarity multiplied by the volume, we can substitute these values into the equation.

M1V1 = M2V2

(cont.)

(cont.)



Sample Problem #1 – Calculate the volume of a known solution needed to dilute to a new molarity.

• What volume of 0.75 M glucose is needed to make 1 liter of 0.15 M glucose?

(cont.)

Preparation of Solutions by Dilution



Check-In

• How many grams of glucose would you need to make 100 mL of 1.0 M solution? The molecular formula of glucose is C6H12O6.



Wrap-Up

• Mass of solute, moles of solute, and volume of solution are related to one another by the molecular weight of the solute and the concentration of the solution.

• If you have a certain volume of a solution of a specified concentration, then you know how many moles of solute you have.


Lesson 7:

Is It Toxic?



ChemCatalyst

Suppose you wanted to determine if your tap water contained lead sulfate, PbSO4 (which is toxic).

• Do you expect the weight of 100 ml of pure water to be the same as that of a 100 ml solution containing PbSO4? Explain your reasoning.



The Big Question

• What does the mass of a solution reveal about the concentration and the molar mass of its solute?




Deduce some differences among solutions that look identical.



Activity

Purpose: You will determine the

identities of solutions given to you by

your instructor, and decide which is safe

to drink.

(cont.)



Safety note: Do not get NaOH on your skin. In case of a spill, rinse with large amounts of water. Wear goggles.

(cont.)

(cont.)



Making Sense

• Examine the toxicities given below. Which solution would be most harmful if you drank it? Which would be least harmful to drink? Explain your thinking.

(cont.)



Salt Molar

mass

Mass of 1.0

moles salts

Approximate

mass of 50 mL

KCl 74.55 g 74.55 g

NaBr 102.89 g 102.9 g

NaOH 40.00 g 40.00 g

(cont.)



Check-In

• Place the following 1.0 M solutions in order of increasing mass, from the smallest mass to the largest mass: NaCl, KCl, and CaCl2.



Wrap-Up

• Solutions have different masses depending on the molar mass of the solute.

• Pure water weighs exactly 1.0 g per 1.0 mL. If 1.0 mL weighs more or less than this, then the water is not pure.

Toxins Unit

Documents

Transcript of Toxins Unit