Activity 30 1. Which water sample tasted best to you, and why? 2. would you spend the extra money on bottled spring water, after your taste-test experience? Why or why not? 3. Some people might disagree with your decision for Analysis question 2. what reasons do you think they would give for their opinion? 4. Reflection: what other information about spring, tap, and distilled water would you like to investigate further before you decide which water to drink? Activity 31 Activity 32 Activity 25- Conservation of Mass 1. What evidence do you have that a chemical reaction took place between:
a. Copper chloride solution and aluminum? b. Copper chloride solution and sodium hydrogen phosphate? 2. What can you conclude about the effect of a chemical reaction on the mass of reactants in a closed system? Support your answer with evidence from the activity. 3. Using what you now know about the Law of Conservation of Mass, how would you respond if a company said it had developed a way to make hazardous materials and wastes disappear? Activity 33 Activity 34
Activity 35- Mystery Liquids 1. Review the Data Table below: Some Properties of Five Liquids Liquid Water Methanol Ethanol Isopropanol Acetone Appearance Clear Clear Clear Clear Clear Smell None Yes Yes Yes Yes Shape of a drop on plastic Round Flat Flat Flat Flat Density (g/ml) 1.000 0.791 0.789 0.786 0.790 Boiling Point (ºC) 100 65 78 82 56 Melting Point (ºC) 0-94 -117-90 Undefined a. Based on your data and the table above, what could liquids A and B be? b. Why do you think so? c. How certain are you? 2. In this activity you compared two liquids. What properties and measurements were the most helpful in identifying the two liquids? Explain your answer. 3. A liquid forms rounded droplets because of its degree of cohesiveness. Which of the two liquids was more cohesive? Explain the observations that support your answer. 4. Why should you keep liquid samples capped or covered while studying them? 5. Which do you predict would evaporate more quickly at room temperature: methanol or acetone? (Refer to the data in Table 1.) Explain why. 6. Follow steps a, b, c, and d. Copy the four lists into your notebook. a. Look for a relationship among the words in List 1. Cross out the word or phase that does not belong. b. In List 1 circle the word or phrase that includes the other three. c. Explain how the word or phrase you circled is related to the others. d. Repeat steps a c for each of the remaining lists. List 1 List 2 List 3 List 4 Liquid Density Odor Property Solid Boiling Point Feel Cohesive Gas Quantitative Property Color Liquid Cohesive Color Temperature Comparison Melting Point Qualitative Property Clear Activity 36 see next page
Activity 37: What Dissolves 1. In this investigation, which substance(s) are solutes and which are solvent(s)? 2. A substance that dissolves in water can be described as soluble in water. a. List the four solids in order from most to least soluble in water. 1. 2. 3. 4. b. Explain what evidence enabled you to order the substances by solubility. 3. a. Must a mixture be clear to be a solution? Explain. 3b. Must a mixture be colorless to be a solution? Explain. 4. Imagine that all four of the tested solids are considered water pollutants. Which would be easiest to remove from the water? Explain your answer.
Activity 38: Dissolving Duel 1. Which solvent/solute pairs dissolved completely? What is your evidence? 2. a. Which solvent/solute pairs seemed not to dissolve at all? What is your evidence? b. In these cases how might you test to be sure you are correct that none of the solute dissolved? 3. Which solvent/solute pairs dissolved partially? What is your evidence? 4. List at least two ways that water s ability to dissolve substances: a. can be helpful to people and other living organisms. b. can be harmful to people and other living organisms. Activity 39
Activity 40 Activity 45: Precipitating Specific Contaminants 1. What was the contaminant in this activity? 2. What evidence indicates that a chemical reaction occurred when you mixed solutions of sodium carbonate and copper chloride? 3. a. You added sodium carbonate solution to the copper chloride solution. Where do you think the solid that appeared came from? b. Why does that substance get trapped by the filter paper? c. What property(ies) does (do) all solid precipitates that form and settle to the bottom when two solutions are mixed have? 4. Describe two ways the control in Test 1 helped you analyze the data. 5. a. Did precipitation work for removing the contaminant from the water? Explain, using evidence from the investigation. b. Did your procedure for testing the presence of contaminant in the filtrate work well? How did you know how well it worked? 6. How could the procedure in this investigation be useful for purifying wastewater? 7. Copper is a metal. Look at the Periodic Table of the Elements, and list two other elements that you think this procedure would work well for if they were contaminants.
Activity 46: Investigating Solutions of Acids and Bases 1. Group the nine substances you tested based on how they interacted with the indicators. Acidic (ph <6.7) Neutral (ph 6.8-7.2) Basic (ph > 7.3) 2. Which do you think is the most useful indicator? Explain your answer by considering the advantages of each indicator. 3. What happens to the ph of an acid or a base solution as you dilute it with water? 4. Do you think that dilution with water is a good method for treating industrial waste that contains an acid or a base? Explain the reasons for your answer. 5. Reflection: Think about your experiences tasting or touching everyday substances like vinegar, lemon juice, and detergents that you now know to be acidic or basic. What do the acidic substances seem to have in common? What do the basic substances seem to have in common? Activity 47: Acids, Bases, and the ph Scale 1. In what ways can the ph or acidity of water affect: a. living things, such as fish? b. people? 2. Fill in the blanks of the following sentences with the correct number. a. A solution with a ph of 5 is times as acidic as a solution with a ph of 6. b. A solution with a ph of 4 is times as acidic as a solution with a ph of 6. 3. Compare and contrast acids and bases by completing a Venn diagram. Acids Bases 4. What do you predict will happen to ph when an acid and a base are mixed together? Explain your prediction.
Activity 48: Mixing an Acid and a Base 1. What happens as you add an acid to a basic solution or add a base to an acidic solution? 2. Which solution seems more powerful in this investigation, the acidic or the basic? Explain your answer. 3. Based on what you know so far, which do you think is a better way of neutralizing an acid: diluting it with water, or adding a base? Explain your answer. 4. Given two solutions, how might you determine: a. whether these solutions are acidic or basic? b. which is more acidic or basic? Activity 49: A Model for Acid-Base Neutralization 1. For the example in Procedure Step 1, how many drops of base would be needed to neutralize: a. 2drops of acid? Explain, or draw a diagram to show your reasoning. b. 10 drops of acid? Explain, or draw a diagram to show your reasoning. c. 4 liters of acid? Explain your reasoning. 2. In the example in Procedure Step 2, how many liters of base would be needed to neutralize: a. 1 liter of acid? b. 200 liters of acid? 3. Based on the results from the class, are there more particles of acid in a drop of 1% hydrochloric acid (HCl) or more particles of base in a drop of 1% potassium hydroxide (KOH)? Explain how you figured out your answer. 4. Draw a diagram to show the number of drops of 1% HCl and 1% KOH that would make a neutral solution. Illustrate the ratio of particles in the drops. 5. Given that the HCl and KOH solutions used in Activity 48, Mixing an Acid and a Base, were 1% (each of them contains one gram of solute per 100 grams of solution), how could you explain that the ratio of particles per drop of the neutral solution is not 1:1?
Activity 50