To quote a friend of mine, "I like being right so much that, when I'm proven wrong, I change my mind."

See this is why I love scientists. When they disagree it doesn’t matter how you feel. One is wrong and the other is right. AND THEY CAN PROVE IT! Nobody leaves mad because you leaned something new

You can tell she answered with no hesitation and followed it up with an exact number. When you know your s*** you know your s***.

For those who mistake Niel's enthusiasm for arrogance. Scientists love to be proven wrong, but they will require proof. That's the part that people mistake for arogance. The fact they don't just take your word for it and that they can back their word with study and experiment.

When Neil feels he knows something, he stands by it. But when he's shown to be wrong he's always humble and asks questions to learn more. Great character!

that "FALSE!" sounded like Sheldon tbh

I just imagine Niel going home and doing it and then going “well I’ll be…”

Hold on... Freezing point depression means that the liquid-to-solid phase change occurs at a lower temperature for saltwater than for pure water. When making ice cream, you need salted water AND ice. With ice equilibrated to a temperature well below freezing (e.g., 0F), the salted water cool and then hold at a lower temperature due to freezing point depression. This is a different phenomenon than an endothermic process leading to a temperature change upon mixing. For example, water will cool appreciably when urea is dissolved into it. That has nothing to do with freezing point depression. I've never seen Neil concede so quickly but, unless there's more to this conversation, I think hhe was correct that the phenomena behind "instant" cold packs and making ice cream are not the same thing.

Intellect is so attractive to me.

That mic drop was appropriate 👌

To clarify Neil's and her points in the context of average and median temperatures, let's break down the scenarios with precise definitions and explanations: ### Average Temperature The average temperature (or mean temperature) is the total thermal energy divided by the mass of water in the glass. When salt is added to ice water: - **Neil's Point**: If we assume no significant loss of heat to the surroundings and the system is isolated, the total thermal energy in the glass with salt may remain approximately the same compared to the plain ice water. This means that the **average temperature** might not differ significantly between the two glasses. ### Median Temperature The median temperature is the middle value of the temperature distribution in the glass. When salt is added: - **Her Point**: The process of adding salt lowers the freezing point of water and causes ice to melt more quickly. This results in a mixture where some parts of the glass have very cold melted water, while other parts are slightly warmer due to the mixing process. This creates a wider distribution of temperatures within the glass. Consequently, the **median temperature** (the midpoint of this distribution) would likely be lower in the glass with salt because of these colder regions. ### Summary - **Average Temperature**: If the system is isolated and no significant heat is lost or gained from the environment, the average temperature of the two glasses might be quite similar. The energy absorbed in melting the ice and dissolving the salt slightly lowers the temperature, but the total heat content distributed over the same mass might keep the average temperature close. - **Median Temperature**: In the glass with salt, the rapid melting of ice and the resulting pockets of very cold water lead to a lower median temperature. This means there are more colder regions, pushing the median value of the temperature distribution down. ### Conclusion Neil's point about the average temperature remaining the same holds true in an isolated system with no significant external heat exchange. Her point about the median temperature being lower is also correct, as the salt creates colder regions within the mixture. Therefore, both points are valid within their respective contexts: the average temperature might stay similar, while the median temperature in the glass with salt will be lower due to the presence of very cold areas from the melting ice.

Okay we need to see a video of Neil doing the experiment. I'm going to follow this with baited breath.

Basically, when you dissolve salt like NaCl, it dissociates into Na⁺ and Cl⁻ ions, and this process requires energy which is absorbed from the surroundings.

To the Learning Cave!

Things kind of got mixed up there, pardon the pun, salt lowers the freezing point of a solution but does not cause the solution to get cold. Cold packs get cold because the mixing process of the ionic compound and water is endothermic, sucking heat out of the surroundings. I don't recall if table salt mixing in water is endothermic, but if it is, it is very minimally endothermic, not nearly enough to freeze ice cream. The ice you use to freeze the ice cream is much colder than zero Celsius, but the salt allows the liquid/ice solution to get colder than zero when the solution would normally be limited to zero.

2 scientists enter 1 scientist leaves..

Incorrect. She explained why water cools down when you add some salts (some have the opposite effect) in water by accurately describing the cryoscopic constant of water. The phenomena that explains the change of temperature when you add different salts in water is called enthalpy of dissolution. These two phenomena are unrelated.

Dr.Niel is implicitly teaching us how to reason professionally and correctly

This made me so happy to see Niel is such a great role model, takes a big man to be able to handle being wrong so gracefully

It's also why they salt the roads before and after it snows/ices in the winter. The salt lowers the freezing point of water, allowing the snow/ice to melt at a lower temp than normal.

Hope NDT has some calamine lotion for that burn.

God this is refreshing discourse that ends in a goal to test a new hypothesis right or wrong this is what ideological debates should yield not screaming or popularity contests

She’s beautiful and extremely smart and a kind person.

The one-upper is one-upped! Neil met his match😅 My new favorite video on the entire internet. Next time Neil…next time

I love the experiment gauntlet!! 😮😅

Yay! I knew this, it's in my high school chemistry book! Probably the only time I'm gonna know something that Neil doesn't!

Put salt in water... quite a vague couple of parameters. ... it goes down by minus 1.86⁰C... quite presice 🤔 Also we put salt on icy roads to melt ice not freeze it further. Freezing point depression is when a solute is added to a solvent the maximum temperature at which the solution freezes drops.

If the temperature goes down by a negative 1.86 Deg C. it increases. It warms up. (Double negative) It agtually goes down by 1.86 deg.C. making it colder. But I also agree with Mr. D.T. as in addition to temperature drop the ice melts and makes a slurry without warming, increasing the heat exchange from the cream churn to the slurry.

easy experiment: put salt on the back of your hand and rub it with ice 😂

It's a discussion, and he simply gave his opinion and said that he would test it. He didn't sound dogmatic.

Freezing point depression is not the reason for the temperature change during dissolution. Instead, it is the enthalpy of mixing. If the energy required to separate the solute particles is greater than the energy released during the solvation of the solute particles, then the dissolution process would absorb heat/energy from the surroundings resulting in cooling of the surroundings (lowering of temperature). This process can also be exothermic if the energy released in solvation of solute particles is greater than the energy required to separate the solute particles. In this case, heating would be observed. Freezing point depression is a different phenomenon where WE HAVE TO cool a solute-solvent mixture to a lower temperature for freezing to take place. This is because the entropy of mixture is greater than that of the pure solvent. Therefore, there is more disorder present in the mixture and further cooling is required to obtain the less disordered solid state of the solvent (i.e. freezing).

Neil is absolutely right here. Salt lowers freezing point, not related to temperature change.

if it goes DOWN by -1.86°C, doesn't that mean that delta t is +1.86°C? Language is so easily misunderstood, I love it.

Neil needs to do this with Terrance Howard

It depends on the salt. If you dissolve Ammonium Nitrate in water, the temperature will drop, it is an endothermic reaction. If you dissolve Calcium Chloride in water, the temperature will rise, it is an exothermic reaction. They may be confusing another thing called the freezing point depression that occurs when a salt is dissolved in water. It also raises the boiling point.

Absolutely love it. Experiment time!

Freezing point depression isn't the same as lower the temperature. More confused after this than before lol

Neil: Lady what? Speak English please

“Do not correct a fool, or he will hate you; correct a wise man, and he will appreciate you.”

She deserves a medal a trophy and a special ceremony for having corrected Neil de GT and kept him quiet for a few precious seconds of victory. :) although I have to admit I am Neils number one fan😊

Adding salt to water affects both its boiling and freezing points due to the phenomenon known as colligative properties, which are properties that depend on the number of dissolved particles in a solution. 1. **Boiling Point Elevation**: When salt (or any solute) is added to water, it causes the boiling point of the water to increase. This is known as boiling point elevation. The salt ions disrupt the formation of vapor bubbles within the liquid, requiring a higher temperature to reach the boiling point. In simple terms, the presence of salt makes it harder for water molecules to escape into the gas phase, so the water must be heated to a higher temperature to boil. 2. **Freezing Point Depression**: Adding salt to water lowers its freezing point, a phenomenon called freezing point depression. The salt ions interfere with the formation of the solid ice structure, making it harder for water molecules to align into a solid form. As a result, the solution needs to be at a lower temperature than pure water to freeze. This is why salt is often used to melt ice on roads in winter; it lowers the freezing point of water, causing ice to melt even at temperatures below the normal freezing point of 0°C (32°F). In summary, adding salt to water elevates the boiling point and lowers the freezing point due to the disruption caused by the dissolved salt ions in the molecular structure and phase changes of water. The phenomena of boiling point elevation and freezing point depression can be described using colligative property formulas. Here are the key formulas and explanations: 1. **Boiling Point Elevation**: \[ \Delta T_b = i \cdot K_b \cdot m \] - \(\Delta T_b\) is the increase in the boiling point. - \(i\) is the van't Hoff factor, which represents the number of particles the solute dissociates into (for NaCl, \(i = 2\) because it dissociates into Na\(^+\) and Cl\(^-\)). - \(K_b\) is the ebullioscopic constant (boiling point elevation constant) of the solvent (for water, \(K_b \approx 0.512 \, \text{°C kg/mol}\)). - \(m\) is the molality of the solution (moles of solute per kilogram of solvent). 2. **Freezing Point Depression**: \[ \Delta T_f = i \cdot K_f \cdot m \] - \(\Delta T_f\) is the decrease in the freezing point. - \(i\) is the van't Hoff factor. - \(K_f\) is the cryoscopic constant (freezing point depression constant) of the solvent (for water, \(K_f \approx 1.86 \, \text{°C kg/mol}\)). - \(m\) is the molality of the solution. ### Example Calculation: If we add 1 mole of NaCl (table salt) to 1 kg of water: 1. **Determine the van't Hoff factor**: - NaCl dissociates into Na\(^+\) and Cl\(^-\), so \(i = 2\). 2. **Calculate the molality**: - Since we have 1 mole of solute (NaCl) in 1 kg of solvent (water), the molality \(m = 1 \, \text{mol/kg}\). 3. **Boiling Point Elevation**: \[ \Delta T_b = i \cdot K_b \cdot m = 2 \cdot 0.512 \, \text{°C kg/mol} \cdot 1 \, \text{mol/kg} = 1.024 \, \text{°C} \] So, the boiling point of water would increase by approximately 1.024°C. 4. **Freezing Point Depression**: \[ \Delta T_f = i \cdot K_f \cdot m = 2 \cdot 1.86 \, \text{°C kg/mol} \cdot 1 \, \text{mol/kg} = 3.72 \, \text{°C} \] So, the freezing point of water would decrease by approximately 3.72°C. These calculations demonstrate how the addition of salt affects the boiling and freezing points of water, making it boil at a higher temperature and freeze at a lower temperature.

Freezing point depression just means that the water has a lower freezing temperature. That doesn't lower the temperature of the water.

Still seems like two different things. Salt added to ice when making ice cream lowers the melting point of the ice so it can absorb heat at a temp below the normal freezing point. In the ice pack example, a solid is dissolved into a liquid. In many cases this is exothermic but can spread strongly endothermic for some combination. So the first is energy involved in a change of state. The second is energy involved in dissolving.

quick correction adding salt to water doesn't make the water itself colder, but it lowers the freezing point of the water. This means that the water can remain in liquid form at temperatures below 0°C (32°F), which is the normal freezing point of pure water. So, the addition of salt allows the water to be colder without freezing, but it doesn't lower the actual temperature of the water on its own.

NDT not afraid to ADMIT he is WRONG!

This makes sense, because I've heard chef's say that adding salt to water increases the time it takes for the water to boil. I never understood why...until now.

I can't believe he conceded so quickly and readily... She literally said what he's always maintained, that it lowers the freezing point... Which is different from an endothermic reaction (the ice packs) causing "temperature depression" aka a perceptible cooling of the mixture When you salt your driveway in the winter, it lowers the freezing point of the salt water solution so it doesn't easily refreeze (which causes all the tiktok videos of people slipping and falling)... According to her, the driveway would suddenly get way colder than it already is

Kudos to Tyson posting him being corrected. It’s outside of his field of expertise

This is Great! The smile on her face as she thinks "oh Damn! Neil is WRONG and I get to Tell him". With Zero hesitation. ❤🎉

Adding salt lowers the freezing point of water. You do not change tempurature by adding salt to water, lol. Neil was trying to be nice I think. Adding salt for ice cream is related to changing freezing points as well.

Need the follow up video!!! I wanna see Neil doing SCIENCE!!

Chuck is low key BRILLIANT hiding behind his comedy.

Girl came prepared with NUMBERS 😂😂

I wish more people were like this! Neil: I think this because reason Guest: False! And heres the equation Neil: Well damn, I was wrong

That’s why putting salt on an icy road or path works. Lowers the freezing point and causes the water to stay liquid.

hmmm... salt in liquid water lowers the temp? perhaps..... didn't know that... but it definitely lowers the temp of a liquid ice mixture. A slush of pure liquid water stays at 32F..... half liquid half ice....all heat change works on state change solid/liquid at constant temp of 32F. But add salt that changes the state temp transition to a lower temp. This is how an icre maker works. You put a metal bowl in the salt slush. metal transfers heat well. The salt slush temp drops to about 20F or so while the cream still freezes around 32F F.

I believe her argument is fallacious: she mentions freezing point depression, which is distinct from the equilibrium temperature of the just-combined salt and water mix in room temperature conditions.

To make water take longer to boil add salt, has a new meaning now.

Adding salt doesn't lower the actual temp of the water. It drops the freezing point from 32F to approx. 27F. That's why they don't put salt on roads when the temp is extremely cold because it won't work.

Neil: "I would claim..." She: false (fórmula) Neil: (accepted. I was wrong) by how much Gotta love science

I’m so like Neil, I love physics, but I cannot for my life understand anything about chemistry 😭

He knows about salt and water (he’s an astrophysicist) they probably did this as a stunt to get people watching to engage in experimentation and try this themselves. And hey, I’m all for that!

I add magnesium chloride to my ice baths, it makes it colder & it absorbs best from your skin.

Here's the experiment. Put a bowl of water and bottle of water in the fridge. Take them both out, put a bunch of salt and ice into the water, put the bottle of water into the water. The salty water will become colder than 32 F. The ice will melt and make supercooled water, and the supercooled water should freeze the water in the bottle which doesn't have the salt. It doesn't decrease the temperature directly, though; it allows the ice to decrease the temperature.

NDT's face while you're talking in the middle of his conversation: 😐

I love it when Neil talks as though an authority outside his field of astrophysics and pretends to know more than actual experts in those fields... and then challenges experts in those fields and loses. STAY IN YOUR FIELD, NEIL!!!

Ok elevation of freesing point is a colligative property that increases the freesing point of the solution but it wont actually change the temperature the temperature is constant but it just solidifys

What I don't get is why does salt melt ice if salt lowers the temperature of water?

She just tricked Neil DeGrass Tyson into the Ice-Salt challenge from early internet

I like it when Neil gets taught something he is the smartest person in the room so often that he like all of us need to be humbled ever so often!!

Freezing point depression and temperature reduction are not the same thing. yes the freezing point of water is lower when there is dissolved salt putting salt in water doesn’t lower the temperature of the water you put the salt in, unless the salt is cold.

She almost had to defend herself. I'm glad Tyson listened and respected her. You saw the defense in her for just a second.

Mixing salt in water does indeed depress the freezing point of water. It does not lower the temperature of the water, however, and that is not how a cold pack works.

This is a great example of difference between wisdom and knowledge about something. Neal obvious had more to say, about why salt is used with ice cream (obviously 1.86 degree change doesn't help make ice cream). But she was SO SURE that she was CORRECT, she basically started yelling proof it makes the slight difference it does in fact make, and he just moved on.

NDT is my favorite science spokesperson, but he is far from an expert in pretty much any field lol. Watching him get corrected by practicing doctors of their respective scientific field is fun to watch in person, he always handles it comically and with humility, which is why we all love him.

I love a man who can accept when he's wrong, but will still do a lil science cause he needs to EXPERIENCE the RIGHTNESS my goodness I just love Neil 😊

Adding salt to water does not decrease its temperature in the context of making the water colder. However, it does lower the freezing point of the water, which is a phenomenon known as freezing point depression. This means that saltwater can get colder without freezing compared to pure water. For example, when salt is added to ice, it causes the ice to melt at a lower temperature than usual. This is why salt is often used to melt ice on roads. The actual temperature of the water does not decrease because of the salt itself, but the presence of salt can allow the water to stay liquid at temperatures below 0°C (32°F). So Neil is right.

love when neil learns things

Why can't I be this knowledgeable about chemistry like this instead of video games.

I am impressed with a nice responses.!

It's what we always did to ice beer down faster ice water in a cooler with salt will chill your alcoholic beverages realy guickly especially if you circulate the water! Ice is 32° but that mixture drops well below 32°

The chemical reactors in these ice packs are typically ammonium nitrate, calcium ammonium nitrate, or urea... The absorb the heat in the water and make it cold

I just got home and did this experiment with a thermoter. The water was 68.7 degrees F then added salt and it went up a degree just from sitting out on the counter while I waited. It did not go down at all. This person is wrong. That equation shows that the freezing point of the salt+ water mixture is lower, not the temperature itself. When salt mixes with ice it melts the ice by bringing down the freezing point which then leaches thermal energy from the surrounding area because changing states from solid to liquid will absorb energy. That lowers the temperature of the surrounding area which is how you make ice cream. Salt mixed with liquid water doesn't automatically lower temperature.

some type of endothermic reaction, not just mixing salt and water. Mixing salt and water will move freezing and boiling points but its not a chemical reaction

Never seen Neil Tyson get owned so profoundly

It only makes sense. If you have a mixture of ice and water without salt, that mixture will remain at 32F until all the ice is melted. Adding salt lowers the freezing point, allowing more ice to melt at a colder temp, lowering the temperature of the mixture. That is exactly why salt is used to make ice cream. I'm really surprised Neil didn't know this.

"I don't think-" She pulls out the "delta t is equal to -ikf times molality" freezing point depression. Mic drop. Neil stands corrected. Can't argue with that.

Her equation-spouting made my gray matter rigid

I did the experiment. Sorry Neil.

Freezing point depression means it will lower the freezing point yeah? But just putting salt into water won’t make it freeze or change the temperature enough to make that big of a difference to touch. Theres a thing called btu’s. You have to remove thermal units somehow. So, something in the chemical makeup expands the volume more than co2 would so that it would be able to absorb more thermal units. Like a drink that’s almost frozen but not (carbonated) then you pop the top and release the pressure holding the water inside of the drink to a liquid and bam. Ice crystals

Neil: you got this packet…. Her: 🙂‍↕️😃😁😄🙂‍↕️

They dont use it just for the lowering of temp it also melts the ice making cold water that can touch more of the container instead of just the points of the ice cooling it faster

Did You See Him Blush!? I Think Neil Found That Scientific Exchange Quite Stimulating. He Loves Science!! And We Love Neil!

I'm just glad to see someone shut him up by proving him wrong!

Salt doesnt simply reduce the heat. It will allow the water to get colder, but it does not make the water colder. A quick google search showed that ice packs contain water and another ingredient. It probably does include salt, but it wont work with just those 2 ingredients

This is how a scientist responds. Has an idea. Makes a claim. Genuinely asks questions. Immediately tests theory. Immediately

They are actually both right and wrong in this instance. Originally they were talking about instant ice packs, where a salt like ammonium nitrate is dissolved in water to instantly lower the temperature because the reaction in endothermic and has a positive enthalpy. Adding salt to ice cream disrupts the water from forming a solid lattice as well as it normally would which lowers the freezing point of the icecream and keeps it softer as well by having smaller irregular crystal structures I believe. So while Tyson was correct about it being for a different reason, the lady was correct that it does lower the freezing point. Very fun related concepts, though!

I love to see him be wrong and called out on it! Especially by a woman!! Feels good man.

And that's how science works! "I'll use your methodology to either prove or disprove your claims" instead of just yelling from the extremes of political spectrums. We need to vote for scientists.

All due respect for NDT, but you've gotta love when someone who knows more about a particular topic is able to immediately and confidently put his foot back into his mouth for him. And hey, props for taking it in stride. That's the best thing about science, like, oh we disagree? Experiment or research, but we will both know the answers on the other side.