Activity 40 Follow-upActivity 40 Follow-up

Understanding Serial Dilutions Understanding Serial Dilutions and Concentrationand Concentration

One drop of red dye solution

One drop of water

Activity 40 AnalysisActivity 40 Analysis

1.1. Which is more dilute, Cup 1 or Cup 2? Which is more dilute, Cup 1 or Cup 2? How do you know this?How do you know this? Cup 2Cup 2 The color in cup 2 is lighterThe color in cup 2 is lighter We know we mixed one part of the original We know we mixed one part of the original

solution to nine parts of watersolution to nine parts of water

2.2. If Cup 1 has a concentration of one part If Cup 1 has a concentration of one part in 10, and Cup 2 has 1/10 the in 10, and Cup 2 has 1/10 the concentration Cup 1, what is the concentration Cup 1, what is the concentration in Cup 2?concentration in Cup 2? One part per 100One part per 100

3.3. Which cup has a concentration of one Which cup has a concentration of one part of food coloring per one million part of food coloring per one million parts of solution?parts of solution? Cup 6Cup 6

4.4. What is the number of the cup in What is the number of the cup in which the solution first appeared which the solution first appeared colorless? What is the concentration colorless? What is the concentration of the solution in this cup? Hint: of the solution in this cup? Hint: Express the answer for concentration Express the answer for concentration as one part per ___.as one part per ___. Usually it’s Cup 5, 6, or 7 (varies with Usually it’s Cup 5, 6, or 7 (varies with

techniques and ability to see colortechniques and ability to see color Cup 5 is 1 part per 100,000Cup 5 is 1 part per 100,000 Cup 6 is 1 part per 1,000,000 or 1ppmCup 6 is 1 part per 1,000,000 or 1ppm

5.5. Do you think there is any food coloring Do you think there is any food coloring in Cup 8, even though it appears in Cup 8, even though it appears colorless? Explain.colorless? Explain. Was there a direct observation (evidence) Was there a direct observation (evidence)

to support your conclusion)to support your conclusion) You might infer that there must be some You might infer that there must be some

food coloring present since it was in the food coloring present since it was in the original solution that became colorless original solution that became colorless with dilutionwith dilution

An inference is a conclusion that is not An inference is a conclusion that is not based on direct observationsbased on direct observations

Look at the tray with evaporated solutionsLook at the tray with evaporated solutions You might conclude that particles are You might conclude that particles are

present in Cups 8 and 9, but there are not present in Cups 8 and 9, but there are not enough to observe directlyenough to observe directly

Imagine that the food coloring is a Imagine that the food coloring is a toxic substance. Do you think that toxic substance. Do you think that diluting the substance with a lot of diluting the substance with a lot of

water will make it safe?water will make it safe? A more dilute solution may not be A more dilute solution may not be

harmfulharmful It will not be completely gone and It will not be completely gone and

may still cause problemsmay still cause problems In Activity 34, “Water Pollution”, you In Activity 34, “Water Pollution”, you

read some substances, such as read some substances, such as bacterial contaminants, are harmful in bacterial contaminants, are harmful in very small amountsvery small amounts

The Willow Grove Story:The Willow Grove Story: Activity 41Activity 41

Willow Grove’s well water, Fenton River and Willow Grove’s well water, Fenton River and Willow Lake were tested to make sure they met Willow Lake were tested to make sure they met federal water-quality standards.federal water-quality standards.

The results showed Willow Lake water was turbid The results showed Willow Lake water was turbid (cloudy due to presence of impurities), Fenton (cloudy due to presence of impurities), Fenton River water was slightly acidic, and the well water River water was slightly acidic, and the well water contained nitrates.contained nitrates.

Test for iron used potassium thiocyanate and Test for iron used potassium thiocyanate and hydrochloric acid---a reddish orange color indicated the hydrochloric acid---a reddish orange color indicated the presence of iron (test can detect 500 ppm or higher)presence of iron (test can detect 500 ppm or higher)

Test for nitrates used hydrochloric acid and a powdered Test for nitrates used hydrochloric acid and a powdered nitrate indicator---purple = nitratesnitrate indicator---purple = nitrates

Test for copper using ammonia---light blue = copper Test for copper using ammonia---light blue = copper levels over 2 ppmlevels over 2 ppm

Results indicated:Results indicated:

Willow Grove needs to treat the Willow Grove needs to treat the groundwater to remove nitrates---50% of groundwater to remove nitrates---50% of the residents drink well waterthe residents drink well water

The town should figure out what is The town should figure out what is causing the acid in the river to prevent causing the acid in the river to prevent levels from risinglevels from rising

The town should figure out what is making The town should figure out what is making the lake turbid, but it is still safe since it is the lake turbid, but it is still safe since it is treated by the water districttreated by the water district

Activity 42 Water PurificationActivity 42 Water Purification Two treatment methods used by most water Two treatment methods used by most water

districts to remove contaminants before districts to remove contaminants before piping water to homes are coagulation and piping water to homes are coagulation and filtration.filtration.

Coagulation involves using chemicals to Coagulation involves using chemicals to attract contaminants into large clumps. The attract contaminants into large clumps. The clumps settle to the bottom of the water clumps settle to the bottom of the water tank. Filtration traps and separates solid tank. Filtration traps and separates solid contaminants from the water by making the contaminants from the water by making the water flow through filters.water flow through filters.

Alum was added to dirty water to coagulateAlum was added to dirty water to coagulate Filtration tubes were filled with gravel, sand, and Filtration tubes were filled with gravel, sand, and

charcoalcharcoal

Cleaning the Water at a Cleaning the Water at a Water-Treatment PlantWater-Treatment Plant

Title: Precipitating Specific

Contaminants

Activity 45

Read C-78Read C-78

Problem: How can you use a chemical reaction to remove a contaminant from a solution?

Hypothesis/Initial Thoughts:

Chemical Reaction……Chemical Reaction…… What terms or ideas relate to this What terms or ideas relate to this

Color change (of a solution)Color change (of a solution) Energy change—temperature change, Energy change—temperature change,

light, or generation of electricitylight, or generation of electricity Odor changeOdor change Disappearance of an original substance Disappearance of an original substance

(reactant consumption)(reactant consumption) Formation of bubbles (gaseous product)Formation of bubbles (gaseous product) Formation of a precipitate (solid product)Formation of a precipitate (solid product) Change in the results of a chemical test Change in the results of a chemical test

(such as a pH change detected with an (such as a pH change detected with an indicator)indicator)

Dissolving is of a chemical Dissolving is of a chemical change. It is a physical changechange. It is a physical change

The solute can be reclaimed by a physical means The solute can be reclaimed by a physical means of separation: evaporation of the solventof separation: evaporation of the solvent

In this activity, dissolved copper chloride will In this activity, dissolved copper chloride will represent a wastewater contaminantrepresent a wastewater contaminant

Dissolved sodium carbonate is the solution Dissolved sodium carbonate is the solution added to enable the contaminant to be added to enable the contaminant to be precipitated out and removedprecipitated out and removed

CuClCuCl22 (aq) + Na (aq) + Na22COCO33 (aq) (aq) CuCO CuCO33 (s) + NaCl (aq) (s) + NaCl (aq)Copper chloride + sodium carbonate copper carbonate + sodium Copper chloride + sodium carbonate copper carbonate + sodium

chloride chloride

This is called precipitation which is different than This is called precipitation which is different than precipitation that forms when water vapor precipitation that forms when water vapor condenses in clouds and falls to the earthcondenses in clouds and falls to the earth

NOT EVIDENCE

Data/Observation:Data/Observation:Table: Precipitation ReactionTable: Precipitation Reaction

One pair do tests 1 and 2

One pair do tests 3 and 4

Make observations before and after you mix them

Make comparisons in your descriptions like, “lighter than or less than test 1”

Goggles on!Goggles on!

Start with Start with procedure step procedure step

4 4 in your book!in your book!

step 4step 4

Decide which pair will do tests 1 Decide which pair will do tests 1 and 2 and which will do tests 3 and 2 and which will do tests 3

and 4and 4Follow the instructions on your table to determine Follow the instructions on your table to determine

the number of drops of water and sodium the number of drops of water and sodium carbonate you add to Cups B and Ccarbonate you add to Cups B and C

A B C D E

Test 1 or 3

Test 2 or 4

Write down what you see Write down what you see before you stir the mixture before you stir the mixture

and after you stir the and after you stir the mixture. Be descriptive!mixture. Be descriptive!

Examples: blue, bluish-green, fluffy Examples: blue, bluish-green, fluffy solid, cloudy, thick, darker blue than…, solid, cloudy, thick, darker blue than…,

clear, pasty, fizzing, chunks, clear, pasty, fizzing, chunks, precipitateprecipitate

Fold two filter papers, moisten them, Fold two filter papers, moisten them, and place them into two filter funnel and place them into two filter funnel openings. openings.

Place the filter funnels onto Place the filter funnels onto your SEPUP tray so that the your SEPUP tray so that the openings are over Cups D openings are over Cups D

and Eand E

A B C D E

A B C D E

Using the dropper, transfer as Using the dropper, transfer as much as you can of the material much as you can of the material from Cup B to the filter in Cup D. from Cup B to the filter in Cup D. Rinse the dropper and transfer Rinse the dropper and transfer

Cup C material to E.Cup C material to E.

Once the mixtures have Once the mixtures have filtered, observe the filtered, observe the

appearance and quality of appearance and quality of the filter paper. Then put the filter paper. Then put the filters in a paper towel the filters in a paper towel and put them in the trash. and put them in the trash. Observe the appearance Observe the appearance

and quantity of the filtrate. and quantity of the filtrate. Finish filling in the data Finish filling in the data

table on your student sheet.table on your student sheet.

How could you test the How could you test the filtrate to see if there is any filtrate to see if there is any

copper chloride in it? copper chloride in it?

Add 1 one drop of sodium carbonate Add 1 one drop of sodium carbonate and observe any change. Continue to and observe any change. Continue to add a drop at a time pausing for add a drop at a time pausing for observation until you reach 10.observation until you reach 10.

Clean-upClean-up

Everyone wash Everyone wash hands with soap hands with soap and water.and water.