Activity 37 Analysis

1. In this investigation, which substance(s) are solutes and which are solvent(s)?

• Sodium chloride and copper chloride are solutes • Water is the solvent each time • Part of iron chloride is the solute (water turned a clear brownish color), most didn’t dissolve • Cornstarch was not a solute

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.

• • • • • •

b. Explain what evidence enabled you to order the substance by solubility

Copper chloride, sodium chloride, iron chloride, cornstarch All 5 scoops of copper chloride dissolved in the water Liquid in the filter remained light blue 1 scoop of sodium chloride dissolved completely & not quite all of the 5 scoops did Iron chloride is only slightly soluble; water became slightly brown and most remained solid; stayed in the filter Cornstarch least soluble; appeared to mix in but settled out if it sat; amount in the filter looked like original amount; liquid was clear after filtering (milky white before)

3. a. Must a liquid be clear to be a solution? Explain.

• Yes • If it isn’t clear, there are still large particles in the mixture

b. Must a mixture be colorless to be a solution? Explain.

• No • Copper chloride completely mixed in and it was blue • It’s a solution even if it has color

4. Imagine that all four of the tested solids are considered water pollutants. Which would be easiest to remove from the water? Explain.

• Cornstarch • Particles don’t dissolve; can be removed with a filter • Most of the iron chloride could be removed with a filter

Design your own experiment

• In activity 38, you will write your own procedure and design a data table to collect the data.

• You are going to test the ability of several different solids to dissolve in two liquids: ethanol and water • What are the solvents?

• What are the solutes?

Title:

Dissolving Duel

Activity 38

Read C-43

Problem:

Do substances dissolve better in water or in ethanol?

Hypothesis:

Fill in the chart below and check the box under the solvent you think will work better to dissolve the material.

Substance Dissolve better in water Dissolve better in ethanol Substance Dissolve better in water Dissolve better in ethanol Cornstarch Sugar Sodium Chloride Iron Chloride Lauric Acid Copper Sulfate Neronline Yara Yara

Design a procedure & data table

• Use the procedure in activity 37 as a guide • Make sure your experiment is reproducible (someone could read your procedure and do it exactly as you did-- don’t leave any steps out) • The purpose is to compare the solvents, consider whether you need to vary the number of scoops you use for each solute.

• Design a data table • What type of results are important to record?

• Work in your group on a separate sheet of paper (one person write it) to brainstorm ideas and steps for your procedure • Do not write your procedure or data table in your notebook until it has been approved by your teacher • Think of a way to minimize the amount of each solvent and solute you use • Compare your procedure with other groups to get feedback

Sample Procedure

1. Decide which team of two will use water as the solvent and which will use ethanol.

2. Place one level scoop of each solute in the appropriate 3.

cup (as listed in the table).

Add 10 drops of your team’s solvent to each cup.

4. Use the stir stick to stir each cup for 30 seconds. Clean 5.

the stick after stirring each substance.

Record your team’s observations in your data table.

6. Trade trays with the other team, and record your own observations of their mixtures in your notebook data table.

Data/Observation:

Table: Comparing Solubilities in Water and Ethanol

Or two tables:

Results: