Experiment 12: Colloids (Part A)

Summary

This script outlines a chemistry experiment involving colloids, where a dialysis bag is used to separate components in a solution. The process begins with preparing the dialysis bag by tying it to a stir rod and filling it with starch and sodium chloride solutions. The bag is then submerged in deionized water for half an hour to allow diffusion. After removing the bag, the solution from the beaker is tested for starch and sodium chloride presence using iodine and silver nitrate reagents, respectively, in a series of test tubes.

Takeaways

• 🧪 Start by preparing a dialysis bag, ensuring it is wet and loose for easy handling.
• 🪢 Tie one end of the bag with a string to create a seal.
• 🗑 Insert a funnel into the bag to facilitate the addition of solutions.
• 📐 Add 10 mL of 1% starch solution and 10 mL of 1% sodium chloride solution into the bag.
• 🔗 Secure the other end of the bag and attach it to a stir rod for hanging.
• 🥣 Place 50 mL of distilled water into a 400 mL beaker and immerse the dialysis bag, allowing it to sit for 30 minutes.
• ⏳ Wait for the dialysis process to complete, which will separate the contents of the bag from the beaker's water.
• 🗑 Discard the contents of the dialysis bag and retain the solution in the beaker.
• 🧫 Transfer 5 mL of the beaker's solution into two separate test tubes for further testing.
• 🧪 Perform the iodine test on the 1% starch solution and the solution from the beaker using iodine reagent.
• 🧪 Conduct a silver nitrate test on the 1% sodium chloride solution and the solution from the beaker to observe reactions.
• 🔬 The experiment aims to demonstrate the dialysis process and the reactions of starch and sodium chloride with iodine and silver nitrate, respectively.

Q & A

What is the purpose of using a dialysis bag in the described experiment?

The dialysis bag is used to separate molecules of different sizes, allowing smaller molecules to pass through while retaining larger ones, which is essential in the study of colloids.

Why is the dialysis bag worked loose with fingers before tying it?

Working the dialysis bag loose ensures that there are no air bubbles trapped inside, which could interfere with the diffusion process during the experiment.

What is the role of the string in the experiment?

The string is used to tie the dialysis bag, securing the contents inside and preventing them from mixing with the external solution.

How much starch solution and sodium chloride solution are added to the dialysis bag?

10 milliliters of each, a 1% starch solution and a 1% sodium chloride solution, are added to the dialysis bag.

Why is the dialysis bag tied to a stir rod?

Tying the dialysis bag to a stir rod allows it to hang and be fully submerged in the beaker, facilitating the diffusion process.

What volume of di water is added to the beaker before placing the dialysis bag inside?

50 milliliters of di water are added to the 400-milliliter beaker.

How long is the dialysis bag left to sit in the beaker of di water?

The dialysis bag is left to sit for half an hour to allow sufficient time for diffusion.

Why is the solution from the dialysis bag discarded after the experiment?

The solution inside the dialysis bag is not needed for the subsequent tests, and the focus is on what has diffused into the beaker.

What is the purpose of the ten doll test performed on the test tubes?

The ten doll test is likely a typographical error; it should be the 'Tollen's test,' which is used to detect the presence of aldehydes. However, in this context, it seems to be a reference to observing reactions with iodine and silver nitrate reagents.

What reagents are added to test tubes one and two, and what is the purpose?

One drop of iodine reagent is added to both test tubes one and two. This is to observe any color change that would indicate the presence of starch or a reaction with the solution from the dialysis bag.

What is the significance of adding silver nitrate to test tubes three and four?

Adding silver nitrate to test tubes three and four is to test for the presence of chloride ions, as silver nitrate reacts with chloride to form a white precipitate of silver chloride.

Outlines

00:00

🧪 Dialysis Bag Preparation and Experiment Setup

The script describes a scientific procedure involving a dialysis bag. The process begins with preparing the dialysis bag by wetting it and loosening one end to tie a knot. A funnel is inserted into the bag, and 10 mL each of 1% starch solution and 1% sodium chloride solution are added. The bag is then sealed and attached to a stir rod. A 400 mL beaker is filled with 50 mL of di water, and the bag is submerged for 30 minutes. Afterward, the dialysis bag is removed, and its contents are discarded, while the solution in the beaker is retained. Five mL of this solution is taken for further testing.

05:01

🔬 Chemical Testing and Observations

This paragraph outlines a series of chemical tests. Five mL of the solution from the beaker is transferred to a second test tube, and another five mL is taken for a different test. The script then details the addition of 5 mL of 1% starch solution to test tube one and 5 mL of 1% sodium chloride solution to test tube three. The ten doll test is performed on both test tubes, involving the addition of iodine reagent to each. Test tube one, with the starch solution, and test tube three, with the sodium chloride solution, are both tested. Additionally, a drop of 1% silver nitrate is added to test tube three and another to test tube four, which contains solution from the beaker the dialysis bag was in. The purpose of these tests is to observe chemical reactions and identify the presence of specific compounds.

Keywords

💡Dialysis Bag

A dialysis bag is a semipermeable container used to separate molecules based on their size. In the video, the dialysis bag is used to separate the larger starch molecules from the smaller sodium chloride molecules in an aqueous solution, demonstrating the principle of dialysis.

💡Starch Solution

A starch solution is a mixture where starch is dissolved in water. It is used in the video to represent a colloidal substance that cannot pass through the dialysis bag, thus illustrating the selective permeability of the bag.

💡Sodium Chloride Solution

Sodium chloride solution, or saltwater, is a common aqueous solution where sodium chloride is dissolved in water. In the script, it is added to the dialysis bag to show that smaller ions can pass through the bag's membrane, unlike the larger starch molecules.

💡Knot

In the context of the video, a knot is used to secure the open ends of the dialysis bag. This is crucial for containing the solutions within the bag and ensuring that only the desired molecules can pass through the membrane into the surrounding water.

💡Funnel

A funnel is a tool used to pour liquids or powders into containers with a narrow opening. In the script, a funnel is placed inside the dialysis bag to facilitate the addition of solutions without spilling.

💡Stir Rod

A stir rod is used to mix or stir solutions in a container. In the video, the dialysis bag is tied to a stir rod to hang it in the beaker, allowing the solutions to mix and the dialysis process to occur.

💡Beaker

A beaker is a container used for mixing, stirring, and heating liquids in a laboratory. In the script, a 400-mil beaker is filled with di water, and the dialysis bag is placed inside it to allow the diffusion of molecules through the bag's membrane.

💡Di Water

Di water, or deionized water, is water that has had its ions removed, making it highly pure. In the video, di water is used to fill the beaker, providing a medium for the dialysis process to take place.

💡Iodine Reagent

Iodine reagent is a chemical used for testing the presence of starch. In the video, it is added to the starch solution and the solution from the beaker to test for the presence of starch after the dialysis process.

💡Silver Nitrate

Silver nitrate is a chemical compound used in various laboratory tests, including the detection of chloride ions. In the script, it is added to the sodium chloride solution and the solution from the beaker to demonstrate a reaction that indicates the presence of chloride ions.

💡Test Tube

A test tube is a piece of laboratory glassware used as a container for chemical reactions on a small scale. In the video, test tubes are used to hold different solutions for testing and comparison after the dialysis process.

Highlights

Starting the dialysis process by taking out the dialysis bag from water and loosening it with fingers.

Tying a knot at one end of the dialysis bag using a string.

Placing a funnel inside the dialysis bag to add solutions.

Adding 10 mL of 1% starch solution into the dialysis bag.

Adding 10 mL of 1% sodium chloride solution to the dialysis bag.

Tying the other end of the bag and attaching it to a stir rod.

Filling a 400 mL beaker with 50 mL of di water.

Placing the dialysis bag inside the beaker and letting it sit for half an hour.

Removing the dialysis bag from water and discarding its contents.

Transferring the solution from the beaker to test tubes for further testing.

Performing the ten doll test on test tube number one containing 1% starch solution.

Adding iodine reagent to test tube number one for the ten doll test.

Adding 1% sodium chloride solution to test tube number three.

Adding silver nitrate to test tube number three for a chemical reaction.

Adding silver nitrate to test tube number four containing solution from the beaker.

Observing the chemical reactions and outcomes in the test tubes.

Discarding the dialysis bag's solution as it is no longer needed.

Conducting a series of tests to analyze the properties of the solutions.

Transcripts

for part a of colloids

we're going to take our dialysis bag out

of

water we are going to work this

loose with our fingers

on one end

I will tie a knot in the bag

using this string

on the other end that I have worked

loose place a funnel inside

going to add 10 mils

of my 1% starch solution

going to add 10 mils of my 1% sodium

chloride solution

and now tie the other end of the bag

once I have the bag tied

then tie it to stir rod

so then now the bag can hang from the

stir rod

then going to put in the turn 50 mils of

di water into the 400 mil beaker

I will then place the bag inside the

beaker and let that sit like so

for half an hour

we are going to remove the dialysis bag

from the water

we do not want what's in the dialysis

bag we want what's now in the beaker so

I will take the dialysis bag

put the solution in a waste beaker

we no longer need that

we will take five mils of this solution

from the beaker

put this in our second test-tube

take another five mils

for this intestine number four

now we will take five mils of our 1%

starch solution

add that to test-tube number one

take 5 mils of my 1% sodium chloride

solution

and I will add that to chest tube number

three

we will now perform the ten doll test on

test tube number one which contains five

mils of 1% starch solution

we will now do it on test tube number

three which has five mils of one percent

sodium chloride

I will now add

one drop of iodine reagent two test tube

number one and two

test tube number one is five mils of 1%

starch solution one drop of iodine

reagent

test tube number two is five mils from

the beaker that the dialysis bag was

soaking in

I will now add a drop of 1% silver

nitrate to test tube number three which

is 5 mils of our 1% sodium chloride

solution

I will now add a drop of silver nitrate

to test tube number four which contains

five mils of the solution from the

beaker the dialysis bag was in

you