Making YOU the Scientist: Freezing Point Depression and Phase Changes

Summary

This educational video demonstrates how to freeze water without a freezer by leveraging the principles of freezing point depression and phase changes. The experiment involves creating an ice-water slurry, adding salt to lower the freezing point below zero degrees Celsius, and then using this mixture to freeze pure water in a test tube. The video also explains the concept of colligative properties and their applications, such as de-icing roads and car radiators, and making ice cream.

Takeaways

• 🧪 The experiment demonstrates freezing water without a freezer by leveraging the concepts of freezing point depression and phase changes.
• 🌡 To start, room temperature water is mixed with crushed ice to create an ice-water mixture, which initially measures at 0°C.
• ❄️ Freezing point depression is achieved by adding salt to the ice-water mixture, which lowers the temperature below 0°C.
• 🧂 The addition of salt disrupts the formation of hydrogen bonds in water, preventing it from freezing until a lower temperature is reached.
• 🕒 The experiment uses a test tube with pure water to show how the salt-depressed ice-water mixture can freeze water in a short time.
• ⏱️ A stopwatch is used to time how long it takes for the water in the test tube to freeze when placed in the cold saltwater bath.
• 🔍 The experiment visually shows the phase change from liquid to solid as the water in the test tube freezes within minutes.
• 🌟 Colligative properties, such as freezing point depression and boiling point elevation, depend on the number of solute particles, not the type of solute.
• 🛣️ Real-world applications of freezing point depression include using salt on roads to prevent ice formation and adding antifreeze to car radiators.
• 🍨 An interesting application mentioned is the use of freezing point depression in the making of chocolate ice cream to achieve a desirable texture.
• 📚 The video script provides a link to a detailed write-up of the experiment for those seeking more information.

Q & A

What are the two main physics topics discussed in the video?

The two main physics topics discussed in the video are freezing point depression and phase changes.

What is the goal of the experiment presented in the video?

The goal of the experiment is to freeze water without using a freezer by utilizing the principles of freezing point depression.

What materials are needed for the experiment as mentioned in the video?

The materials needed for the experiment include a thermometer, salt, ice, crushed ice, a test tube, a stopwatch, water, and beakers or glasses.

How does the addition of salt affect the freezing point of water?

Adding salt to water causes the freezing point to decrease because the salt ions disrupt the formation of hydrogen bonds between water molecules, thus requiring a lower temperature for the water to freeze.

What is the initial temperature of the ice-water mixture in the experiment?

The initial temperature of the ice-water mixture is at 0 degrees Celsius, which is the freezing point of pure water.

How does the video demonstrate the concept of freezing point depression?

The video demonstrates freezing point depression by adding salt to an ice-water mixture, causing the temperature to drop below 0 degrees Celsius, which is the normal freezing point of water.

What is the role of stirring in the experiment?

Stirring the mixture in the experiment ensures that the salt is evenly distributed and helps the temperature to decrease uniformly, showcasing the effect of freezing point depression.

How long does it take for the water in the test tube to freeze when placed in the saltwater mixture?

It takes approximately four minutes for the water in the test tube to freeze when placed in the saltwater mixture, which is colder than 0 degrees Celsius.

What is a colligative property and how does it relate to the experiment?

A colligative property is a physical change that occurs when a solute is added to a solvent, and it depends on the number of solute particles rather than the type of solute. In the experiment, adding salt (solute) to water (solvent) demonstrates the colligative property of freezing point depression.

What are some real-world applications of freezing point depression mentioned in the video?

Some real-world applications of freezing point depression include using salt on roads to prevent ice formation during winter, using antifreeze in car radiators to prevent the engine's water from freezing, and in the process of making chocolate ice cream.

Outlines

00:00

🧪 Experimenting with Freezing Point Depression

The first paragraph introduces an educational video on scientific experiments focusing on freezing point depression and phase changes. The presenter outlines a hands-on experiment that can be conducted at home using basic items like a thermometer, salt, ice, a test tube, and water. The goal is to freeze water without a freezer. The experiment begins by creating an ice-water slurry and measuring its temperature, which initially reads 0°C. The presenter then demonstrates how adding salt to the mixture lowers the freezing point below 0°C, as evidenced by the thermometer readings. This part of the experiment concludes with the use of the saltwater-ice mixture to freeze pure water in a test tube, showcasing the practical application of freezing point depression.

05:00

🔬 Understanding Colligative Properties and Freezing Point Depression

The second paragraph delves into the scientific principles behind freezing point depression and boiling point elevation, emphasizing that these are colligative properties. These properties are influenced by the presence of solutes in a solvent, regardless of the solute's identity. The experiment uses sodium chloride (salt) as a solute, but the principle applies to any solute that can be added to a solvent to lower the freezing point. The presenter uses a model to illustrate how salt ions interfere with the formation of hydrogen bonds necessary for water to solidify, thus requiring a lower temperature for freezing. Applications of this principle are discussed, including the use of salt on icy roads to prevent ice formation, the use of antifreeze in car radiators to prevent freezing, and its role in making ice cream. The paragraph concludes with a call to action for viewers to engage with the content by subscribing, notifying, commenting, liking, and sharing the video.

Keywords

💡Freezing Point Depression

Freezing point depression is a colligative property that occurs when a solute is added to a solvent, resulting in a lowering of the solvent's freezing point. In the video, this concept is demonstrated by adding salt to an ice-water mixture, which lowers the temperature below the normal freezing point of water (0 degrees Celsius). This is crucial for understanding how the experiment manipulates the phase change of water without a freezer.

💡Phase Changes

Phase changes refer to the transformations between the states of matter (solid, liquid, gas) under varying conditions of temperature and pressure. The video focuses on the transition from liquid to solid, specifically freezing. It illustrates phase changes by showing how water in a test tube freezes when placed in a cold saltwater bath, demonstrating the practical application of freezing point depression.

💡Colligative Properties

Colligative properties are physical properties of a solution that depend on the concentration of solute particles, not the nature of the solute itself. The video explains that freezing point depression and boiling point elevation are examples of colligative properties. It emphasizes that the amount of solute added affects the depression of the freezing point, as seen when salt is added to the ice-water mixture.

💡Salt (Sodium Chloride)

Salt, or sodium chloride, is used in the experiment as a solute to demonstrate freezing point depression. When added to water, it dissociates into sodium and chloride ions, which interfere with the hydrogen bonding between water molecules necessary for ice formation. The video shows that by adding salt, the freezing point of the ice-water mixture is depressed to below 0 degrees Celsius.

💡Test Tube

A test tube is a laboratory vessel used in the video to contain pure water that will be frozen using the freezing point depression technique. It is placed in the cold saltwater bath, and the temperature change is monitored with a thermometer. The test tube serves as a practical tool to observe the phase change from liquid to solid.

💡Thermostat

Although not explicitly mentioned, the concept of a thermostat is alluded to in the context of car radiators. Antifreeze, which operates on principles similar to those of freezing point depression, is used to prevent the engine's water from freezing, akin to how a thermostat regulates temperature to prevent damage.

💡Ice Water Mixture

An ice water mixture is created in the video by combining crushed ice with water. This mixture is used as a starting point to demonstrate freezing point depression. The initial temperature of this mixture is at the normal freezing point of water, but with added salt, it is depressed to below 0 degrees Celsius, illustrating the experiment's main principle.

💡Beaker

A beaker is a container used in the experiment to hold the ice-water mixture into which salt is added. The beaker is stirred to ensure the salt is well distributed, and a thermometer is used to measure the temperature change as the freezing point is depressed. The beaker is a key component in conducting and observing the experiment.

💡Stopwatch

A stopwatch is used in the video to time how long it takes for the water in the test tube to freeze when placed in the cold saltwater bath. This tool is crucial for measuring the rate of the phase change, demonstrating the effect of freezing point depression on the freezing process.

💡Pure Water

Pure water is used in the test tube to demonstrate the freezing process. Initially at room temperature, it is exposed to the cold saltwater bath, and its temperature is monitored until it reaches the freezing point and solidifies. The use of pure water in the experiment contrasts with the saltwater mixture, highlighting the effect of solutes on freezing points.

💡Crystal Structure

The crystal structure refers to the ordered arrangement of molecules in a solid. In the context of the video, the crystal structure of ice is mentioned when explaining how water molecules slow down and arrange themselves in a solid form at 0 degrees Celsius. The addition of salt disrupts this process, requiring a lower temperature to achieve the same crystal structure and solid state.

Highlights

Experiment demonstrates freezing water without a freezer by utilizing the concepts of freezing point depression and phase changes.

Materials needed include a thermometer, salt, ice, a test tube, a stopwatch, and water.

Freezing point depression occurs when the temperature of an ice-water mixture is lowered below zero degrees Celsius by adding salt.

The experiment shows that adding salt to an ice-water mixture can depress the freezing point to as low as minus nine degrees Celsius.

A test tube with pure water is used to demonstrate the freezing process in a salt-depressed ice-water bath.

The time it takes for water to freeze in the test tube is measured, showing a rapid freeze in four minutes.

The experiment also explores the phase change from solid to liquid by placing frozen water in a warm water bath.

Colligative properties are explained as physical changes that occur when a solute is added to a solvent.

The type of solute is not as important as the quantity added for the freezing point depression effect.

A model is used to visually demonstrate how salt ions interfere with the formation of hydrogen bonds in water, necessary for freezing.

Practical applications of freezing point depression include using salt on roads to prevent ice formation and in car radiators as antifreeze.

The role of freezing point depression in making chocolate ice cream is mentioned as a tasty application.

The video concludes with a call to action for viewers to subscribe, enable notifications, comment, like, and share the video.

Transcripts

welcome to the next installment in our

making you the scientist

video series today we're going to do an

experiment that involves two

very important physics topics the first

is freezing point depression

and the second is phase changes and the

most interesting thing about this

experiment is what we're going to do is

we're going to freeze water

without using a freezer now to do this

experiment you need some simple things

that you might have around the house

we have a thermometer you can also use a

digital thermometer

just plain old salt ice

crushed ice a test tube a stopwatch a

water and you can see an assortment of

beakers here

if you don't have beakers available of

course you can just use plain old

glasses

all right if you would like more

information about this experiment you

can find that available at my teacher's

pay teacher store

i have a full write-up the link is in

the description below okay as i pointed

out in our introduction we're going to

start the first part of the experiment

with looking at freezing point

depression and to do that we have here a

beaker that is full of crushed ice and

to that beaker

we're going to add some water we want to

add just enough water to wet the ice we

really want to have a slurry of ice

water

mostly ice with some water and then

we're going to stir that up

nicely quick stir and then we're going

to place the thermometer in there

to figure see the temperature of that

ice water mixture you can see when we

start

we have room temperature here is 20

degrees celsius

and then we can place that thermometer

into

our mixture of ice and water just let it

sit for a moment

it should come pretty quickly to zero

degrees celsius now you can see that the

temperature of our ice water mixture is

at

zero degrees celsius now for freezing

point depression

what we want to try and do is we want to

try and get the temperature of that ice

water mixture to go

below zero degrees celsius and to do

that

we're going to add some salt to our

mixture

so we're going to add like five

teaspoons of salt it doesn't matter

exactly how much salt one more and then

you're gonna give it a nice

good stir mix that all up really nicely

there you go

nice stirring and then we're going to

put our thermometer back in and we

should see

pretty quickly that the temperature goes

below

zero degrees celsius we'll let it sit

like that for a moment okay let's do a

quick temperature check

okay you can see already we're at minus

three degrees let's put it thermometer

back in there again

and we can give it a little bit of a

stir of course you're not supposed to be

using your

thermometer to stir move the thermometer

in there like that

and then we'll check the thermometer

temperature one more time

and you can see now we're getting pretty

close to minus five degrees

we'll leave it in there one more time

give it a little bit of a stir

okay now we can check the final

temperature of our water

ice and salt mixture and you can see

that that temperature has come down

very nicely to just about minus 10

degrees i think we're at -9 degrees so

we started

with the water and the ice at zero

degrees celsius we added the salt

we depressed the freezing point to minus

nine degrees and now what we're going to

do is we're going to use that mixture

of water ice and salt to freeze

some pure water so here we have a test

tube

in the tester we have about 10

milliliters of pure water

we're going to place our thermometer in

there and figure out what our

measure what our initial temperature is

we want to write the temperature down

the initial temperature of 25 degrees

we're going to place the test tube

with the thermometer in our water ice

salt bath which has a

temperature less than zero degrees and

then we're going to take our stopwatch

we're going to start our stopwatch and

we want to measure first the amount of

time it takes

for the water in our test tube to come

to

zero degrees celsius okay we're coming

up to one minute let's see we have 50 55

and then we'll just call that one minute

and you can see already

that the temperature of the water in the

test tube has come down

to just about zero degrees we're at two

degrees celsius

and it's dropping below two degrees

celsius so what we're going to do now

is we're going to put that thermometer

and the test tube back

in the ice water mixture and we're going

to mix that up a little bit give it a

good stir

and every minute or so we'll give that a

stir like that and we'll see how long it

takes now

for the water in that test tube to

freeze

solid okay now we're gonna check the

temperature of the water in our test

tube you can see we just have about

four minutes time that's been sitting in

our bath of

water ice and salt so let's see the

temperature

oops look at that the temperature we

can't even read the temperature well i

can't read the temperature because that

water is completely frozen in just four

minutes

we use freezing point depression of our

mixture

to freeze that water and you can see a

solid

froze frozen solid right there in our

test tube

okay now let's see what happens when we

take our test tube with our frozen water

and put it in

a warm water bath perhaps we can get the

thermometer out of there

and separate the thermometer the water

and that test tube

all right let's see let it sit and there

you can see we lift that up

and there goes the test tube slides off

there very nicely

and there you have our thermometer with

our frozen water doesn't that look cool

now i'd like to talk about some of the

physical principles behind freezing

point depression and also

this applies to boiling point elevation

freezing point depression and boiling

point elevation

are colligative properties colligative

properties are physical changes that

occur when a solute

is added to a solvent in our experiment

the solute was the salt the sodium

chloride

and we added that to water which was our

solvent

you should remember that colligative

properties do not depend on the

type of solute that is added so we could

have used any solute we use sodium

chloride you could use another salt such

as

calcium chloride or magnesium chloride

you could use a gas such as oxygen

or you could use another liquid such as

ethylene glycol

all of those can be used to depress the

freezing point

what is important is how many particles

of the solvent that you add

the more salt we add the more we can

lower

the freezing point so remember it's not

the type of solute that's important

but it's how much of the solute you add

to the solvent

now here is a model that i'm going to

show you

try to demonstrate how freezing point

depression works

here we have a model of liquid water

water the chemical formula is h2o and

these are all our water molecules

and this is water at 25 degrees celsius

so we would have this in the liquid

phase

you can see the water molecules are

randomly oriented and they're not that

close together

in order to freeze this water this pure

water we would have to lower the

temperature

to zero degrees celsius as we lower the

temperature

the water molecules begin to move more

slowly and they start to set up a

crystal structure

and then at zero degrees celsius they

become a solid

and the solid water has this crystal

structure

that looks approximately like that so

that would be solid water

at zero degrees celsius now what we want

to do is we want to depress the freezing

point below

zero degrees celsius in order to do that

we added salt to our water sodium

chloride when you add salt to water you

form

sodium and chlorine ions and what

happens is those

sodium and chlorine ions they simply get

in the way

they physically block the hydrogen

and the oxygen atoms from forming

hydrogen bonds

that allow it to become a solid in order

to become a solid

you would have to lower the temperature

below zero degrees celsius

so this could be water that could be

below zero degrees celsius

it's still a liquid and you can actually

decrease the what temperature

of water to minus 20 degrees celsius

before freezing by adding enough sodium

chloride

there are some very important

applications for freezing point

depression

one of those is in the winter time we

apply salt to roads to keep ice from

forming

in the winter when it's wet and the

temperature goes below zero degrees

celsius

then ice will form on the roads and it

will be hazardous for driving

well if we add salt to the roads we can

depress the freezing point of the water

and the ice will not form as easily

another application is when you put

antifreeze in your car's radiator

the antifreeze which will mix with the

water will keep

the water in your car's engine from

freezing when the temperature gets too

low

and from overheating and boiling when

the temperature gets too high

and of course there's another very

important application

for freezing point depression and that's

for making

chocolate ice cream

that tastes pretty good delicious well

thank you so much for watching our video

if you enjoyed that please do all of the

following five things

subscribe to my channel get all my

excellent physics chemistry and math

videos

click the notification bell so you don't

miss anything leave us a comment in the

comment section below

give us a thumbs up and don't forget to

share this video

thank you so much for watching we'll see

you in the next video