go to section pretest 1.describe the charge and location within an atom of the following subatomic...

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Pretest

1. Describe the charge and location within an atom of the following subatomic particles: protons, electrons, and neutrons.

2. Which of the following is true of molecular compounds but NOT of ionic compounds?

a. consist of two or more elements b. are found in nature c. contain ionic bonds d. contain covalent bonds

Chapter 8

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Pretest (continued)

3. Conductivity, freezing point, and boiling point are all

a. related to volume. b. chemical properties. c. physical properties. d. mass.

4. True or False: Endothermic processes release energy.

Chapter 8

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Pretest (continued)

5. Which of the following is always true of a polar covalent bond?

a. One atom in the bond has a partial negative charge.b. One atom in the bond is an ion.c. Both atoms in the bond are of the same element.d. Both atoms in the bond have partial positive charges.

6. A sample of O2 gas has a mass of 64.0 grams. How many moles of O2 gas does the sample contain?

Chapter 8

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Pretest (continued)

7. True or False: Double-replacement reactions involve ionic compounds.

8. Describe chemical equilibrium in terms of reaction rates.

Chapter 8

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Interest Grabber

Observing Dissolving

1. Fill a clear plastic cup with water. Describe the physical properties of the water.

2. You will be given a sugar cube. Describe the physical properties of the sugar.

3. Place the sugar cube into the water. Examine it closely. Describe your observations.

4. Stir the water and sugar until you observe no more changes in the mixture. Describe the physical properties of the mixture.

Section 8.1

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Reading Strategy

Comparing and Contrasting

Section 8.1

a. and b. Physical change and ions are present before and after.

c. and d. Chemical change and ions are present after, but not before.

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8.1 Solutions

• Solutions have two parts:

– Solute = substance that dissolves

– Solvent = substance that solute dissolves in

– Can be a solid, liquid, or gas

• Solution takes on state of solvent

– Most familiar are those of water solvents

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8.1

• 3 Ways substances dissolve:

– Dissociation

– Dispersion

– Ionization

• Depends upon type of compound of solute

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8.1

• Dissociation

– Occurs with ionic compounds

– Starts with ions…. Results in ions

– Physical change

– Solvent attractions overcome compound attractions

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8.1

• Dispersion:

– Occurs with polar covalent compounds

– Compound breaks into smaller pieces and spreads out evenly

– Physical Change

– Ex: Sugar and Water

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Dispersion of Sugar in Water

Figure 4

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8.1

• Ionization

– A neutral compound dissolves forming ions

– Chemical change… solute reacts with solvent

– Formation of an acid/base

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8.1

• Properties of Solutions:

– Can be different from the properties of solute and solvent individually

– Ex:

• Conductivity = ability to conduct heat/electricity

• Increasing/Decreasing Freezing Point

• Increasing/Decreasing Boiling Point

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8.1

• Heat of Solution:

– Dissolving can be:

• Exothermic- release heat

• Endothermic – absorb heat

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Factors Affecting Rates of Dissolving

Figure 7

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8.1

• Factors that speed up (alter) rate of dissolving:

– Heat/Temperature

– Surface Area

– Stirring

– Collision Theory: the more collisions, the faster the reaction will occur!!!

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8.1

Reviewing Concepts

• 1. What are three ways that substances can dissolve in water?

• 2. What physical properties of a solution differ from those of its solutes and solvent?

• 3. How does the formation of a solution involve energy?

• 4. What factors affect dissolving rates?

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8.2 Solution Concentration Activity Requirements

Lab ID

Lab Title

Lab Objectives/Purpose

Data Table

Add a column to the right, as you taste each solution, make observations about taste.

3 Analysis Questions

Conclusion Statement

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Interest Grabber

Solute ConcentrationYou will be provided with five clear plastic cups, colored drink mix, measuring spoons, and water. Copy the table below onto a piece of paper. Label the plastic cups 1–5. In each of the cups, dissolve the given amounts of solute into the corresponding amounts of solvent according to the table.

Section 8.2

Cup Solute Amount

Solvent Amount

Color Intensity Rating

1 ½ teaspoon 250 mL

2 1 teaspoon 250 mL

3 2 teaspoons 250 mL


5 1 teaspoon 125 mL

1. Rate each solution with a number 1–4 that corresponds to the intensity of its color (1 = least intense, 4 = most intense). In the table, fill in the color intensity rating for each solution.

Click the mouse button to display the answer.

cup 1 = 1, cup 2 = 2, cup 3 = 3, cup 4 = 4, cup 5 = 3

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Interest Grabber (continued)


Section 8.2

2. Describe the relationship between the amount of solute contained in the solution and the color intensity of the solution.


In general, as the amount of solute added increases, so does the color intensity of the solution.

Cup Solute Amount

Solvent Amount



2 1 teaspoon 250 mL



5 1 teaspoon 125 mL

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Interest Grabber (continued)


Section 8.2

3. Are there any exceptions to the relationship you observed? Explain


Yes. In cup 5, the amount of solute is the same as the amount in cup 2, but the color intensity rating of cup 5 is same as that of cup 3. This difference can be explained by the fact that half the usual amount of solvent was used for the solution in cup 5. For a given volume, as the amount of solute increases, so does the color intensity of the solution.

Cup Solute Amount

Solvent Amount



2 1 teaspoon 250 mL



5 1 teaspoon 125 mL

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Reading Strategy

Previewing

Section 8.2

a. the maximum amount of solute that dissolves in a given amount of solvent at a given temperature

b. What factors affect solubility?

c. and d. How is the concentration of a solution expressed? percent by volume, percent by mass, molarity

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8.2

• Solubility= maximum amount of solute that will dissolve in a given volume of solvent (at a constant temp)

– Unsaturated – solution with under maximum amount of solute

– Saturated – solution with exactly maximum amount of solute

– Supersaturated – solution with super (more) than maximum amount of solute

• Very unstable

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8.2

• Factors that affect Solubility:

– Polarity

• Like dissolves like

– Pressure

• Increase = increased solubility

– Temperature

• Increase = increased solubility

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8.2

• Concentration – measured amount of solute in solvent

– Can be expressed 3 ways:

–Percent by Volume (20%/80%)

–Percent by Mass (2g/8g)

–Molarity

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Solubility of Some Common Substances

Figure 8

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8.2

Reviewing Concepts

• 1. What terms are used to describe solutions with different amounts of solute?

• 2. List three factors that affect solubility.

• 3. What are three ways to measure the concentration of a solution?

• 4. What is the effect of pressure on the solubility of a gas?

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Interest Grabber

Acidic, Basic, or Neutral1. Place three strips of universal indicator paper on a paper towel. Dip a clean stirring

rod into a solution of saltwater. Touch a drop of saltwater onto one strip of indicator paper. Rinse the stirring rod in deionized water. Record your observations.

2. Dip the clean stirring rod into the ammonia cleaning solution. Touch a drop of the ammonia solution onto the second strip of indicator paper. Rinse the stirring rod in deionized water. Record your observations.

3. Dip the clean stirring rod into the vinegar. Touch a drop of the vinegar onto the third strip of indicator paper. Record your observations.

4. Refer to the color chart provided with the indicator paper. Your teacher will explain which colors indicate an acid, which colors indicate a base, and which color indicates a neutral solution. Classify each solution as acidic, basic, or neutral.

Section 8.3

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Reading Strategy

b. a compound that produces hydronium ions when dissolved in water

d. a compound that produces hydroxide ions when dissolved in water

f. any ionic compound that forms when an acid reacts with a base

Section 8.3

Using Prior Knowledge

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Common Acids and Their Uses

Figure 15

Acetic acid CH3COOH Vinegar

Carbonic acid H2CO3 Carbonated beverages

Hydrochloric acid HCI Digestive juices in stomach

Nitric acid HNO3 Fertilizer production

Phosphoric acid H3PO4 Fertilizer production

Sulfuric acid H2SO4 Car batteries

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Common Bases and Their Uses

Figure 17

Aluminum hydroxide Al(OH)3 Deodorant, antacid

Calcium hydroxide Ca(OH)2 Concrete, plaster

Magnesium hydroxide Mg(OH)2 Antacid, laxative

Sodium hydroxide NaOH Drain cleaner, soap production

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Common Salts and Their Uses

Figure 19

Sodium chloride NaCl Food flavoring, preservative

Sodium carbonate Na2CO3 Used to make glass

Potassium chloride KCl Used as a salt substitute to reduce dietary intake of

sodiumPotassium iodide Kl Added to table salt to

prevent iodine deficiency

Magnesium chloride MgCl2 De-icer for roads

Calcium carbonate CaCO3 Chalk, marble floors, and tables

Ammonium nitrate NH4NO3 Fertilizer, cold packs

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Interest Grabber

Concentration

Bottled fruit juice often contains pure fruit juice, sugar, and other ingredients dissolved in water. The concentration of pure fruit juice can vary with the brand. Look at five different samples of juice made from the same fruit. The label of each bottle or carton should tell you the concentration (percent by volume) of pure fruit juice in the beverage.

1. List the concentrations of all five juice samples.

2. Pour a small sample of the juice with the highest concentration and the juice with the lowestconcentration. Taste each juice. What can you conclude about the relationship between the concentration of pure juice and the taste of the juice?

Section 8.4

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Reading Strategy

Comparing and Contrasting

Section 8.4

a. ionizes almost completely when dissolved in water

b. is a strong electrolyte

c. dissociates almost completely when dissolved in water

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The pH Scale Figure 22

Pretest Answers

1. Describe the charge and location within an atom of the following subatomic particles: protons, electrons, and neutrons.

2. Which of the following is true of molecular compounds but NOT of ionic compounds?

a. consist of two or more elements b. are found in nature c. contain ionic bonds d. contain covalent bonds

Protons are positive and located in the nucleus. Electrons are negative and surround the nucleus in an electron cloud. Neutrons are neutral and are located in the nucleus.

Chapter 8

Click the mouse button to display the answers.

Pretest Answers (continued)


Chapter 8

3. Conductivity, freezing point, and boiling point are all

a. related to volume b. chemical properties c. physical properties d. mass

4. True or False: Endothermic processes release energy.



2.00 moles

Chapter 8

5. Which of the following is always true of a polar covalent bond?

a. One atom in the bond has a partial negative charge.b. One atom in the bond is an ion.c. Both atoms in the bond are of the same element.d. Both atoms in the bond have partial positive charges.

6. A sample of O2 gas has a mass of 64.0 grams. How many moles of O2 gas does the sample contain?



Chemical equilibrium is a state in which the forward and reverse reactions are taking place at the same rate.

Chapter 8

7. True or False: Double-replacement reactions involve ionic compounds.

8. Describe chemical equilibrium in terms of reaction rates.

Interest GrabberAnswers

1. Fill a clear plastic cup with water. Describe the physical properties of the water.

Water is a clear, colorless liquid at room temperature.

2. You will be given a sugar cube. Describe the physical properties of the sugar.

The sugar has white, solid crystals that have been pressed into a cubical shape.

3. Place the sugar cube into the water. Examine it closely. Describe your observations.

The sugar mixes with the water making clear trails in the water. The cube breaks up and gets smaller over time.

4. Stir the water and sugar until you observe no more changes in the mixture. Describe the physical properties of the mixture.

The sugar is no longer visible. The mixture appears to have the same properties as the pure water. It is a clear, colorless liquid.

Section 8.1


1. Place three strips of universal indicator paper on a paper towel. Dip a clean stirring rod into a solution of saltwater. Touch a drop of saltwater onto one strip of indicator paper. Rinse the stirring rod in deionized water. Record your observations.

The indicator paper turns green.

2. Dip the clean stirring rod into the ammonia cleaning solution. Touch a drop of the ammonia solution onto the second strip of indicator paper. Rinse the stirring rod in deionized water. Record your observations.

The indicator paper turns blue.

3. Dip the clean stirring rod into the vinegar. Touch a drop of the vinegar onto the third strip of indicator paper. Record your observations.

The indicator paper turns orange.

4. Refer to the color chart provided with the indicator paper. Your teacher will explain which colors indicate an acid, which colors indicate a base, and which color indicates a neutral solution. Classify each solution as acidic, basic, or neutral.

Saltwater is neutral. Ammonia solution is basic. Vinegar is acidic.

Section 8.3


1. List the concentrations of all five juice samples.

Concentrations will vary.

2. Pour a small sample of the juice with the highest concentration and the juice with the lowest concentration. Taste each juice. What can you conclude about the relationship between the concentration of pure juice and the taste of the juice?

Juices with high concentrations of pure juice taste more like the fruit they come from. Juices with low concentrations taste watery or sugary.

Section 8.4

Chapter 8Go Online

Self-grading assessment

For links on solutions, go to www.SciLinks.org and enter the Web Code as follows: ccn-1081.

For links on bases, go to www.SciLinks.org and enter the Web Code as follows: ccn-1083.

For links on pH, go to www.SciLinks.org and enter the Web Code as follows: ccn-1084.

go to section pretest 1.describe the charge and location within an atom of the following subatomic...

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