Phase Changes, Heats of Fusion and Vaporization, and Phase Diagrams 

the problem at the end was indeed enough to comprehend the concepts

lol me too i was like wait thats so easy until the problem came and I was like oh wait lemme watch the video again ahhahah

same

ugh same

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Krinkle same

Just now😕

same bruh.......

awesome! happy to be of help and no worries! my content is for everyone and if you ever can manage to support one day i'll be grateful then :)

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Damn 7 years ago!!!❤

for the heating portions it's the q = ms delta T where heat exchanged is equal to the mass of the sample times its specific heat times the change in temperature. for melting and boiling it's just the heat of fusion or vaporization times the mass of the sample. but keep in mind that water has a different specific heat depending on what phase it is in!

while heating water at (example:30 c) the energy given is used to increase the kinetic energy until the pressure reaches the surrounding pressure. As equilibrium states are more favourable here , the energy is used to change the state rather that increasing the kinetic energy (equals increase in pressure).

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-o2kYyvxtAAQ.html

hmm i'm not sure of the precise numbers! the higher you go in altitude, the lower the atmospheric pressure certainly, and the lower the boiling point of water, and also it gets colder of course, so that's a factor. but i'm not sure of the quantitative specifics.

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-o2kYyvxtAAQ.html

Generally, the latent heat of vaporization is greater.

it stands for specific heat, check out the one or two tutorials prior to this one in the playlist, about heat capacity and calorimetry and thermochemistry

I always recommend using an external source as well. Double check your comprehension with learning from another source as well for full comprehension! and then come back !

im constantly learning from 3-4+ sources to make sure Im getting the full picture and not missing anything. Theres zero shame in doing this to make sure you understand all steps!

correct!

well you can't see individual molecules, so if you steam then certainly some molecules are coagulating to some extent, but it's not in the liquid phase, nor is the vapor emanating from dry ice in the solid phase, it's gas.

if you watch this you'll know how to answer that!

I think during phase change potential energy increasees

once it's a gas it's already at 100, only 15 degrees left to go!

oohh ok. thanks prof!

WHERES THE UPDATE

@@Valeria-pq7hx he died

when a substance changes from one phase of matter (solid, liquid, gas) to another

Water droplets on the outside of cold water bottles are usually condensed water droplets from the air around the bottle. So the water vapor in the air touches the outside of the bottle, cools, and forms the liquid water. I hope that helps.

What you're talking about is condensation. The water from inside the bottle isn't going through the bottle. The bottle is cold, and is making water vapor (water in the air, yes, there is a little) become a liquid. The cold water slows down the molecular moment of some of the water vapor enough to make it become a liquid, and it builds up on the outside of the bottle. Evaporation is different. Evaporation is the process of water doing what is essentially boiling. But evaporation can happen much slower though. For example, if you leave a cup of water out for months, slower, little by little, the water will become gas and go into the air. This is because small amounts of the liquid water have high enough energy (are moving fast enough) to leap from the liquid and go into the air, and become a gas. People often get condensation (what you asked about) and evaporation mixed up. I used to.

Your English is indeed not very good...tbh its a little crappy

@@jagruti_rs now see that would be "a" critic....thank me later.

the third part only involves heating up the steam from 100 to 115

Professor Dave Explains Oh ok thx cuz my chem teacher doesn’t tell us to do that!!!👍🤗

there is always an equilibrium between liquid water and water vapor, even at room temperature. some molecules have enough kinetic energy to enter the gas phase, and some molecules will re-enter the liquid phase. the boiling point is when the vapor pressure equals atmospheric pressure, or when all of the molecules will enter the gas phase.

I didn't know it, about always having liquid and vaporized water at the same time! is it true for every substance? thank you! btw in the phase diagram of water, the line between solid and liquid is bent backwards because of the hydrogen bonds, right? Thank you again!

@@gabriels2395 Good question. The heat to vaporize water at room temperature, comes from the thermal energy of the air into which it evaporates, causing it to cool adiabatically. The water is nowhere near 100 Celsius to boil directly, but it is above its own boiling point at its partial pressure in the air/water vapor mixture. Consider a dry desert with air at 35C and 15% relative humidity. Water's boiling pressure at 35C is 0.0555 atm. This means, up to 5.55% of the air molecules can be water vapor (3.54% by mass). At that point, we'd say its relative humidity is 100% for saturation. For the dry desert air, 15% relative humidity means that only 0.8% of the air molecules are water vapor (0.5% by mass). Now we evaporate the water from liquid to gas, until saturation. It will cool to 18C. At that condition, the water vapor is 2% by molecule population, or 1.2% by mass. Given 1 kg of desert air, it will evaporate 7 grams of water as it saturates. The air loses 17 kJ of heat and the water gains 17 kJ of heat as it transitions from liquid to gas. You can check that this is consistent with water's enthalpy of vaporization at 18C of 2.46 kJ/g and air's constant pressure heat capacity (1 kJ/kg-C).

prolly

Sorry to be that person, but its video.

It is the opposite way

English is a good language

@@yannick5068 🤣🤣🤣

Mee😎😎