How to Grow a Large, Single Crystal: Part 1 (Growing a Seed Crystal)

Summary

This video tutorial from the University at Buffalo introduces the first part of a two-part series on growing large single crystals. The focus is on creating a seed crystal using aluminum potassium sulfate dodecahydrate, dissolving it in distilled water, and allowing it to crystallize through slow evaporation. The process involves heating, stirring, and carefully transferring the solution to a wide dish for optimal crystal growth. Protective equipment is emphasized, and tips on dealing with impurities and harvesting seed crystals are provided, setting the stage for the next video on transforming these seeds into larger crystals.

Takeaways

• 🌱 The video series is about growing a large single crystal, starting with the creation of a seed crystal.
• 🔍 The process involves slow evaporation of a solution to allow crystal nucleation and growth, influenced by local conditions like humidity and room temperature.
• 🧪 The crystallization material used in the demonstration is aluminum potassium sulfate dodecahydrate, which is dissolved in water.
• 💧 Distilled water is recommended over tap water to avoid interference from minerals and ions.
• 🔥 A Pyrex glass beaker and a hot plate are used to dissolve the alum, with a stir plate and magnetic stir bar to ensure even dissolution.
• 🥽 Safety precautions include wearing eye protection to prevent splashes, though gloves are not necessary for handling alum.
• 👀 The solution should be heated to about 45 to 55 degrees Celsius without boiling to dissolve the alum completely.
• 📏 The amount of water used can affect the rate of crystal growth; more water means slower growth, which is preferable for large crystals.
• 🛠️ A wide, flat dish is used for crystal growth to provide more space for crystals to grow without interference.
• 🕰️ The process requires patience as it involves waiting for the crystals to grow, which can be accelerated by reducing the amount of water.
• 🔬 If the solution remains cloudy after heating, it may be due to impurities in the alum, which will settle over time, allowing for a clear solution to be decanted for crystal growth.
• 🌟 Seed crystals are harvested when they are large enough without bumping into each other, using tweezers and a squirt bottle to prevent damage.

Q & A

What is the main topic of the two-part video series?

The main topic of the video series is how to grow a large single crystal.

What is the first step in growing a large single crystal according to the video?

The first step is to grow a nice seed crystal.

What is the crystallization material used in the U.S. Crystal Growing Competition mentioned in the video?

The crystallization material used is aluminum potassium sulfate dodecahydrate.

Why is it important to keep a constant temperature during the crystal growth process?

Maintaining a constant temperature is important for the controlled evaporation of water, which allows the crystals to nucleate and grow at a steady rate.

What factors affect the rate of water evaporation during the crystal growth process?

The rate of water evaporation depends on local conditions such as room humidity and temperature.

Why is distilled water preferred over tap water for the crystal growing solution?

Distilled water is preferred because it lacks the minerals and ions found in tap water that could potentially interfere with the crystal solution.

What type of container is recommended for heating the solution in the video?

A Pyrex glass beaker is recommended because it can be heated without the risk of cracking.

What safety precautions should be taken while preparing the crystal growing solution?

Wearing eye protection is advised to prevent any potential splashing of the solution.

Why should the solution not be boiled according to the video?

Boiling is not necessary as the powder should dissolve at about 45 to 55 degrees Celsius, and boiling could introduce impurities.

What should be done if the solution appears cloudy after heating?

If the solution is cloudy but no solids are visible, it indicates impurities in the alum. The solution should be left undisturbed for about 24 hours to allow the impurities to settle.

How should the seed crystals be harvested for the next part of the experiment?

Seed crystals should be harvested using tweezers and a squirt bottle to prevent the formation of crusty deposits. Only individual crystals with flat surfaces and sharp edges should be selected.

What is the purpose of the seed crystals in the crystal growing process?

The seed crystals serve as a starting point for the growth of larger single crystals in the next step of the experiment.

What is the significance of the size of the seed crystal in the final outcome of the crystal growth?

The larger the seed crystal, the better the chances of growing a large single crystal in the subsequent steps of the experiment.

Outlines

00:00

🔬 Introduction to Crystal Growing

In this first part of the video series, University at Buffalo Chemist Jason Benedict introduces the process of growing a large single crystal. He explains the necessity of starting with a seed crystal and demonstrates the growth process through slow evaporation at a constant temperature. Benedict emphasizes the importance of local conditions such as humidity and room temperature, which affect the rate of water evaporation and crystal growth. The crystallization material used is aluminum potassium sulfate dodecahydrate, which is dissolved in water to create a solution. He also discusses the use of a Pyrex glass beaker and a hot plate for heating the solution, as well as the need for proper protective equipment due to the potential for splashing.

05:03

💧 Dissolving Alum and Preparing for Crystal Growth

Benedict continues the tutorial by detailing the steps to dissolve alum in water, using a beaker and a hot plate. He advises against boiling the solution and recommends the use of distilled water to avoid interference from minerals and ions found in tap water. The solution should be heated to about 45 to 55 degrees Celsius to dissolve the alum completely. If the solution appears cloudy after heating, Benedict explains that this is due to impurities in the alum and advises waiting for 24 hours for the sediment to settle before decanting the clear solution into a crystallization dish. The process of transferring the solution to a wide flat dish is also described, which allows for the growth of larger crystals by providing more space for them to spread out without bumping into each other.

10:04

🌟 Harvesting Seed Crystals for Further Growth

The final paragraph of the script focuses on the harvesting of seed crystals, which are essential for the next stage of the experiment. Benedict demonstrates how to carefully retrieve the seed crystals using tweezers and a squirt bottle to prevent them from drying out and forming crusty deposits. He advises selecting crystals with flat surfaces and sharp edges, avoiding clumps of crystals that are not single entities. The harvested seed crystals are then gently dried with a paper towel. Benedict concludes the video by showing a collection of small seed crystals and a larger one from a previous attempt, highlighting the importance of growing larger seed crystals for the successful growth of a large single crystal in the subsequent part of the experiment.

Keywords

💡Single Crystal

A single crystal refers to a solid material whose atoms, molecules, or ions are arranged in a highly ordered microscopic structure throughout the entire piece. In the context of the video, growing a single crystal is the main objective, and the process involves careful control of conditions to allow for the uniform growth of a crystal from a seed.

💡Seed Crystal

A seed crystal is a small, pre-existing crystal that is used to initiate the growth of a larger crystal. It provides a surface for the deposition of new material from a supersaturated solution. In the video, the seed crystal is grown first and is essential for the subsequent growth of a large single crystal.

💡Evaporation

Evaporation is the process by which a liquid turns into a gas as a result of surface molecules gaining enough energy to escape into the air. In the video, slow evaporation is the method used to grow the crystals, as the water in the solution evaporates, the concentration of the solute increases, leading to crystal formation.

💡Nucleation

Nucleation is the initial stage of crystal growth where atoms, molecules, or ions come together to form a stable nucleus. In the script, nucleation is mentioned as the process that occurs as the solution becomes supersaturated and the crystals begin to form.

💡Aluminum Potassium Sulfate Dodecahydrate

Aluminum potassium sulfate dodecahydrate is a chemical compound often used in crystal growing experiments due to its ability to form clear, well-defined crystals. In the video, it is the crystallization material used to demonstrate the process of growing a seed crystal.

💡Supersaturation

Supersaturation is a state where a solution contains more solute than it can dissolve at a given temperature, leading to the potential for crystal formation. The video describes how the solution becomes supersaturated, causing the alum to crystallize out and form seed crystals.

💡Distilled Water

Distilled water is water that has been purified through distillation, removing impurities and minerals. In the context of the video, distilled water is recommended for crystal growing to avoid interference from minerals and ions present in tap water.

💡Magnetic Stir Bar

A magnetic stir bar is a small, usually cylindrical or spherical piece of metal that is used in conjunction with a magnetic stirrer to mix solutions. In the video, the stir bar is used to ensure the alum is evenly dissolved in the water.

💡Protective Equipment

Protective equipment refers to clothing or gear worn to minimize exposure to hazards or reduce the risk of injury. In the script, the use of eye protection is emphasized when handling the chemical solution to prevent potential splashes.

💡Crystallization Dish

A crystallization dish is a container used for the slow evaporation of a solution to allow crystals to grow. The video describes transferring the solution to a wide, flat dish to provide more space for the crystals to grow without bumping into each other.

💡Harvesting Seed Crystals

Harvesting seed crystals involves carefully extracting the formed crystals from the solution for further use. The video script details the process of using tweezers and a squirt bottle to harvest seed crystals without damaging them or causing them to dry out prematurely.

Highlights

Introduction to a two-part video series on growing a large single crystal.

The necessity of starting with a seed crystal for growing a large single crystal.

Demonstration of crystal growth through slow evaporation at a constant temperature.

The importance of local conditions such as humidity and room temperature on the rate of water evaporation.

Use of aluminum potassium sulfate dodecahydrate as the crystallization material.

Instructions on dissolving the crystallization material in water using a Pyrex glass beaker.

Safety precautions including the use of eye protection during the experiment.

The use of a stir plate and magnetic stir bar to facilitate the dissolution process.

Recommendation to use distilled water over tap water to avoid interference with crystal growth.

The impact of water volume on the rate and size of crystal growth.

Instructions on heating the solution without boiling it to dissolve the alum.

The process of transferring the solution to a wide flat dish for crystal growth.

Advice on decanting the clear solution into a crystallization dish after impurities settle.

Observation of seed crystal formation due to supersaturation of the solution.

Technique for harvesting seed crystals using tweezers and a squirt bottle.

Criteria for selecting seed crystals with nice flat surfaces and sharp edges.

The significance of the size of the seed crystal for the success of growing a large single crystal.

Anticipation of the next video showing the transformation of the seed crystal into a large single crystal.

Transcripts

UNIVERSITY AT BUFFALO CHEMIST JASON BENEDICT: Hi! This is part one of a two-part video series on how to grow a large single

crystal. If you want to grow a large single crystal, the first thing you're

going to need to do is grow a nice seed crystal, and we're going to show you how [Benedict in a chemistry lab.]

to do that coming up next. What I'm showing today is basically the growth

that occurs through slow evaporation. We're trying to keep a constant

temperature, and as the water evaporates, the crystals are going to nucleate and

grow. And this is where the experimentation comes into play, because

the rate at which the water evaporates is all going to depend on the local

conditions: the humidity in your room, the temperature of your room, and so on.

So what will we need to grow our seed crystal? Well, first we need the

crystallization material. If you're involved in the U.S. Crystal Growing

Competition, we're using aluminum potassium sulfate dodecahydrate. This

comes as a white crystalline powder, and you'll see we have 100 grams of it right [Benedict holds up jar of chemical.]

here. What we're going to do is basically just dissolve this in water, [Small plastic dish with white powder in it.]

and once we have that solution, we're just going to let it stand. This is

actually the nice part about crystal growing, is it's mainly a game of sit and

wait. We're going to need to heat up the solution in order to dissolve the alum,

and so for that we have a Pyrex glass beaker. You're going to want to make sure

you use a some sort of a container that's capable of being heated. If you [Benedict gestures toward glass beaker.]

heat the wrong type of container, the container could crack. You could

run into all sorts of problems. So here's our container, and we have here a hot

plate. Okay. If you're doing this at home you may be working from a stove. It's [Benedict points to beaker on hot plate.]

certainly okay to work in pans and metals. The nice thing about working in

in glassware is that you'll be able to see and mark the level of water that

you'll be using. Okay. So we have we have our beaker in this case we have a stir

plate. We have a magnetic stir bar, and we'll go ahead and add that right

now. One thing I would like to say before you get started here is make sure you're

wearing proper protective equipment. Now alum is a fairly benign

substance, so gloves are probably gonna not really be necessary, but certainly

you should wear eye protection because of the possibility of splashing in your [Benedict points to protective glasses he is wearing.]

face, or any other kinds of potential risks. So we

have our stir bar. We'll go ahead and we'll add 100 grams of alum, and now what [Benedict pours white powder from dish into beaker.]

we're gonna do is add water. Now, what type of water to use? You could go

to your faucet and use tap water. However, tap water contains a lot of

minerals and ions and things that can potentially interfere with the

crystal solutions. For folks at home, you can go to the store and pick up a

bottle of distilled water. Use distilled water not drinking water. Again, drinking [Benedict holds a jug of distilled water.]

water is going to have minerals and ions and things like that. So like I said,

we're gonna fill this up to 800 milliliters. Now that doesn't

necessarily mean there's 800 milliliters of water, but the final volume of our

solution will be 800 milliliters, and we're right at around 800 now. This is the [Benedict pours water into beaker holding white powder.]

thing: It doesn't have to be exactly 800. In fact, you're welcome to experiment.

This is the impact that the amount of water will have: The more water, basically,

the longer it's going to take to get crystals, and if you really don't use

enough water, you're going to grow crystals very rapidly and very quickly,

and that's going to be bad in the case of growing a large crystal. So what we'll

do now is we'll turn on the heat and we'll start this thing stirring [Benedict turns on hot plate.]

What's important here is just that you're stirring the solution. So if

you're at home, you can use a spoon. I would generally use a nonreactive

material. I probably wouldn't use a wooden spoon: It can soak up the salt.

So it's probably stay away from wood. But any kind of plastic or metal should

be just fine, and you just want to stir this from time to time and again. What

we're looking for is all of the solid material to dissolve. So again, I'll be

back in just a minute with the solution. TEXT ON SCREEN: Note: You do not need to boil the solution. The powder should dissolve at about 45 to 55 degrees Celcius. [Lighthearted usic plays as powder dissolves into water in beaker.]

BENEDICT: Here we are a few minutes later. As you can see, all the alum has dissolved. We

have a nice clear solution. So you can go ahead and turn off the heat. So what

happens next? Well, this is the part where we want to begin our crystal growth. Now,

you can let the crystals grow in this beaker. You can just set the beaker in a [Benedict taps beaker.]

dark cabinet. Crystals like to grow best somewhere where they're not going to be

disturbed, right? So a dark cabinet is perfect: no light, no vibrations, no big

temperature changes. But personally, I like to give the crystals a bit more

area to spread out. What you're going to see is the crystals are probably going

to start growing on the bottom of the beaker. By using a wide flat dish, the [Benedict taps a wide, flat transparent dish.]

crystals will generally be more spread out, and this gives them the chance to

grow larger without sort of bumping into each other. We can just transfer our

solution. There's a little bit of steam, we can see it's a little bit warm here. [Benedict pours solution from beaker into wide flat dish.]

Now if this is a competition, you have a little bit of solution still in there, so

it's a good idea to maybe spray it out with a little bit of extra water. No big [Benedict grabs squirt bottle and sprays inside of beaker.]

deal. The only thing adding more water will do

is slow down how quickly the crystals grow. So, obviously it's a competition.

It's limited time. You don't want to be too slow, but adding a little bit of

extra water here and there isn't going to hurt anything. And so what we'll do is

place this dish again, in a a dark cabinet really is ideal, and begin [Benedict talks about the flat dish holding the crystal solution.]

the waiting game. I want to quickly run through something you might experience

when dissolving your alum in solution.If you notice that you've heated your water

up to about 50 degrees and it still looks a little bit cloudy, you want to [Benedict taps a beaker holding a cloudy white solution.]

look inside. If you don't see any solids, this cloudiness is actually a

consequence of some impurities that might be found in the alum. Boiling will

not get rid of this cloudiness. If there are no more solids, the alum has

dissolved, and you're done. Don't heat it any more. What we found is

that these impurities that cause this cloudiness will actually

settle to the bottom if you wait about 24 hours. Here's our solution after about

24 hours, all the sediment has settled to the bottom, and now we can just decant [Benedict shows beaker with clear water and white sediment at bottom.]

off the top layer into our crystallization dish. Now you want to do

this carefully, because this sediment at the bottom will re-disburse if you

agitate the beaker too much. So here we go. And we're gonna stop right about [Benedict pours water into large flat dish, leaving white gunk at bottom of beaker.]

there. Okay, so here's our white cloudy precipitate, and now we have a beautiful

nice clear solution of alum, and we're gonna be ready to grow some seed

crystals. Alright. So here we have a solution that has been sitting actually

for a few days. This is the magic of cinematography. We can see our solution

now has crystals. Well why are these crystals in here? Well the reason they're

here is the solution basically became supersaturated. This

amount of water could no longer hold 100 grams of alum. Some of that alum has to

come out of solution and it crystallizes out. These will be the seed crystals that [View of crystals at bottom of a wide flat dish.]

we'll use for the next part of the experiment. Now we're going to harvest

the seed crystals. We have this camera set up right here so that you can get

an in-depth view of what's going on. You want to harvest the seed crystals when

the crystals are as big as they can be without bumping into

each other. And so how do we do this? Well, you're going to want to grab a pair of

tweezers and perhaps a little squirt bottle. Not totally necessary, but it's [Benedict holds up tweezers and squirt bottle.]

helpful because, remember, this solution here is a saturated salt solution, and so

if you pull these things out and just set them down,

the solution will dry and put crusties on the crystal. So what we're [Overhead view of crystals in large flat dish.]

gonna do is go in here and find a nice little crystal. There we go. And give it a [Tweezers pick up a crystal from inside the dish.]

little give it a little squirt, there we are, [Water sprayed on crystal held by tweezers.]

bring it over here, and set it off to the side. Now you're going to want to grab a

few of these crystals because again, these are the seed crystals you're going [Tweezers grabbing a few crystals, one at a time.]

to use, and you might need a couple of attempts. So what you don't want

to grab is something like this. This is not a single crystal this is a whole [Tweezers grab a clump of crystals that looks like rock candy, with many bumps.]

bunch of crystals crusted together, so you don't want to pick up anything like

that. Okay, now that we've retrieved a few of these crystals and gently patted them [Benedict in lab.]

off with a paper towel, we'll take a look at what we've got. You see this little

collection here. The crystals all have very nice flat surfaces, sharp edges. [Crystals on black surface, each less than half the size of a dime.]

They're nice and transparent or clear. It's a really nice little collection. Now

the thing is, these crystals are just a little bit small. In fact, here's a

previous attempt. You can see that it's a much larger crystal, and this would be a [Benedict holds crystal about the width of a dime.]

seed crystal that you guys at home could very easily grow. I know that you can

grow seed crystals better than this, and again, the larger the seed crystal you

can grow, the better off you'll be in the next step of the experiment. And

that's going to conclude our first video. We now have our seed crystal. The next [Benedict in the lab.]

video will show you how to take this seed crystal and turn it into a large [Benedict holds up seed crystal and a large crystal grown in past competition.]

single crystal. So. Hope you enjoyed watching, and we'll see you in the next video!

[Lighthearted music plays.] [University at Buffalo logo on blue background.]