Formation Definition and 480 Threads

I would like to know if anyone else has seen this (photo below). I put a tray of purified water in my freezer and by the time it had half-way frozen, inch long ice shards at about a 45° angle had formed, grown right up out of the surface of the water. Can anyone point me to an explanation of...

Hello! I have a geology question; a subject which I know next to nothing about. Regarding tectonic plates, I heard someone suggest that when there is oceanic trench formation, it is always accompanied by mountain/hill formation. The websites I have looked at say that there MAY be mountain...

So I was reading through a textbook and came across the term 'close encounter' but no definition or explination of what it means. From what I can make out, I would assume it's referring to asteroid interaction with young galaxies and the role in forming galaxies and stars but this is all...

standard entropy of formation ?? Homework Statement the standard entropy of formation of magnesium is 32.7 J/mol k , That of oxygen gases 205.2 J/mol k at that magnesium oxide is 26.9 J/mol k . A) What is the entropic energy change when 25 grams of magnesium are burned inexcess...

the standard entropy of formation of magnesium is 32.7 J/mol k , That of oxygen gases 205.2 J/mol k at that magnesium oxide is 26.9 J/mol k . A) What is the entropic energy change when 25 grams of magnesium are burned inexcess oxygen at 25 celsius ?? B) Does the burning of magnesium in...

G'day. i'm a 2nd year Aero engineer student from Australia. I've had this question on my mind for the past few days now and can't seem to find much material on it. i was just wondering how the lightest elements (hydrogen and some helium) managed to come together in the center of the solar...

i did an experiment the other day where i split water into hydrogen and oxygen but i used a silver anode and cathode when i turned on the batterie the silver one i think the anode start to corrode( one the one that oxygen forms on) is this making silver oxide when this happens?

Homework Statement An alpha particle is bombarded on 14 N. As a result a 17 O nucleus is formed, and a particle is emitted. This particle is a: (a) neutron (b) proton...

Using Methane gas as an example (CH4 gas), explain why one can not assume the heat of combustion is the reverse of the heat of formation. I can't find a decent answer to this anywhere.

Can someone explain to me the fundamental understanding of why, when two hydrogen atoms for example, release energy when they form a covalent bond? I can't seem to comprehend. Here is my reasoning, please see if this makes any sense of I am simply going in the wrong direction, I would really...

Homework Statement The number of vacancies in a metal increases by a factor of six when the temperature is increased from 800K to 1000K. Calculate the energy for vacancy formation assuming that the density of the metal remains the same over this temperature range. Homework Equations Nv= N...

Homework Statement The standard enthalpy of formation for liquid water is -285.8 kJ / mole. Which of the following could be the standard enthalpy of formation for water vapor? A) -480.7 kJ / mole B) -285.8 kJ C) -241.8 kJ / mole D) +224.5 kJ / mole Homework Equations The...

Why do we need helium for star formation?

Apparently, in the early universe, stars were massive - ranging up to about 500 solar masses. Furthermore the metallicity (elements other than H, He) in the early universe was effectively zero with only hydrogen, helium and trace amounts of lithium. Apparently, stars could reach large masses...

Hello!:wink: May I ask for a little assistance in filling in the gaps of my understanding? :S I understand that the current large scale structure of the Universe is thought to be the result of early fluctuations in density which have been stretched out in the expansion of the Universe. I...

Nuclear reaction leading to formation of C^14 ? Hello. I've got two questions from the NPRE class. One of them is to estimate how old the certain wook piece contained some amount of C^14 is. I solved it. The real question is the second one which is " Write down the nuclear reaction...

Just got back from Lanzarote and was walking through a recent (300yr old Timenfaya) lava field. Very little rain in 300 years so it's more or less like it started, I guess. A great landscape to investigate the way volcanic landscapes develop. What I couldn't understand was the structure of the...

Homework Statement If the focal length of the concave lens is -7.50 cm, at what distance d_o from the lens should an object be placed so that its image is formed 3.70 cm from the lens? What is the magnification m produced by the concave lens described in above? Where should the object be...

Write formation reactions at 1 atmosphere pressure and 25°C for each of the following substnaces: Mercury (I) chloride solid Nitroethane (CH3CH2NO2) liquid I have absolutely no idea how to do this. If anyone can help show or explain to me how to solve this, I'd appreciate it

Homework Statement Using the enthalpies of formation given below, calculate ΔH°rxn in kJ, for the following reaction. 3NO2(g)+1H2O(l) -> 2HNO3(g)+1NO(g) NO2 (g): 33.10 kJ/mol H2O (l): -285.83 kJ/mol HNO3 (l): -174.10 kJ/mol NO (g): 90.29 kJ/mol Homework Equations dHrxn =...

Hi, I'm trying to understand how exactly a black hole fits into the evolution of red supergiants, especially in terms of a timeline. I understand that when the core of the star collapses, it reaches a point where the neutron pressure overcomes it's gravitational force and this deceleration...

Quick question: why are the standard heats of formation 0 for pure elements?

For example, if we have 2-butanol, a compound with a secondary \alpha carbon and I reacted this with HCl and NH4Br I would get 2-bromobutane (via nucleophillic substitution), but how would I determine whether this goes via SN1 or SN2 to achieve this? Now, if this was 1-bromobutane, I know...

Is it common for rocky planets to form closer to a star and gas planets further? Why or why not is this?

What is the chance of planets forming from gas clouds without a star? has anyone calculated this? are they more likely to form than stars? could there be billions of rogue planets floating arround our galaxy?

Basically, I need confirmation on the heat produced when four mole of H2O is produced from Hydrogen and oxygen gas. I'm getting something ridiculous, basically saying that the temperature goes up to ~4000 degrees C. What I'm doing is using Hess's law to find the energies of reaction. H2 and...

Homework Statement Ozone can be prepared from molecular oxygen by subjecting oxygen to an electrical discharge. The standard free energy of formation of ozone is +163.4kJ/mol. a) write the chemical equation for the formation of ozone. b) what sign of the entropy change for this...

1. Can anyone please explain in detail How a Vortex if formed. I mean what are the reasons and physical phenomena that cause the water entering a bath tub sink to gain a CIRCULAR ROTATIONAL motion and form a Vortex. How do the water molecules otherwise traveling straight towards the sink...

its being said, " more the loss of energy, more the strength of the covalent bond" revered members, could u explain why? thanks in advance

I understand the measurement process is sometimes divided into 1) a "premeasurement" which consists in the formation of correlations between system and apparatus (entanglement) and.. 2) a choice between the different eigenvectors of the observable's operator. I would like to understand...

Hi! I've been trying to find explanations about the theoretical formation of naked singularities, and all I could come up with was Wikipedia, and frankly, the explanation didn't "set" in my mind, I couldn't really visualize it. It reads: "From concepts drawn of rotating black holes, it is...

Hello, Having a spot of bother here trying to understand the glass formation in metallic glasses. Could anyone please explain or point me to a source that explains in details structure and kinetics in glass formation? Thanks

And if we increased the size of our imaginary planet, how massive and large could it get before it undergoes fusion? Also, I'm pretty sure you could never actually get a Uranium planet, but is there enough to have Uranium asteroids in a star system, or at least asteroids that are radioactive...

Hi, I am in my second year at Sixth Form College and I have chosen to do Crater Formation for my second year physics coursework. I took some readings and found that a lighter ball makes a deeper crater than a ball of the same diameter but greater mass. I don't know why this is. I would expect...

I was reading something about formation of black hole, and it was given that exclusion principle has a role in BH (Black Hole) formation. It read "when star become small, the matter particle get very near each other, and so acc. to Pauli's Exclusion principle they must have different...

Hello - I'm having some problems understanding Gibbs energy of formation, and how it's applied to electrolysis. So, I'm hoping someone can explain what I'm doing wrong.. According to his site: http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/electrol.html (image) The change in the Gibbs...

Homework Statement Sorry if this kind of question is atypical for this forum. I'm trying to understand the physical concepts involved in my chemistry class. My homework is covering lattice enthalpy, and to get the lattice enthalpy of an ionic compound using the Born-Haber Cycle...

Hi All, I´m quite new to physics (from a biology background) and am hoping someone can give me a quick explanation of what causes the Earth to have a magnetic field. I have read about the dynamo theory but am finding it difficult to visualise or is it as simple as moving currents make an...

band gap arises due to lattice potential.band gap is produced at zone boundary due to bragg reflection.there it behaves like standing wave instead of traveling wave?further formation of 2 standing waves?please help

Homework Statement Please help! i just need to see one step by step solution of how to solve this problem and then I can figure the rest out. When .560g of Na (s) reacts with excess F2(g) to form NaF(s), 13.8 kj of heat is evolved at standard state conditions. What is the standard enthalpy...

I'm currently writing a computer simulation (in Java) of the formation of a helix from a spinning thread. The analogy I use is to imagine a piece of thread held between two fingers and left to hang via gravity. When the thread is spun by rolling one finger against the other, the thread will...

I'm currently writing a computer simulation (in Java) of the formation of a helix from a spinning thread. The analogy I use is to imagine a piece of thread held between two fingers and left to hang via gravity. When the thread is spun by rolling one finger against the other, the thread will...

Homework Statement Three positive point charges are arranged in a triangular pattern in a plane, as shown below. The Coulomb constant is 8.98755 × 109 N · m2/C2. Find the magnitude of the net electric force on the 2 nC charge. Answer in units of N. Homework Equations Fe = (kq1q2) / (d2)...

No, this is not about whether or not Farrah has an STD. I don't know whether this belongs in Physics or Engineering, so feel free to move it. In a normal day, I have a need to apply one drop of water at a time to something. A drip rate of anywhere from 1/2 second to about 3 seconds is...

Homework Statement For the reaction A-->2B+C, the following data are obtained for [A] as a function of time: t=0min, [A]=0.80M; 8min, 0.60M; 24min, 0.35M; 40min, 0.20M. Calculate the rate of formation of B at t= 28 min. The Attempt at a Solution I have found out that this equation is a first...

Understanding the first star formation is critical to cosmology. Matt Turk is a (remarkably young) expert on this. The way they go about it is with computer simulations and checking the results against whatever can be observed. Here is a talk by Matt Turk...

Homework Statement What is the formation of an amide Label all reactants and products Homework Equations O ll The Attempt at a Solution R-C-NH2

For a gas and dust cloud to collapse under gravity to form a star and planets, is the concept of friction important at all? In other words: let's consider a large number of billiard balls, no internal degrees of freedom, participating in completely elastic collisions, with random initial...

I am reading some theoretical papers on the defects in semiconductors. Theorists can calculate the formation energy of a certain kind of defect. If the number is too big, this defect is very unlikely to be seen. So what does this “formation energy” mean? Is that the energy necessary to move...

Hello! Homework Statement If a chemical is used to inhibit spindle formation, what phases would you not see [under a microscope]? 2. Possible answers Prophase Prometaphase Metaphase Anaphase Telophase The Attempt at a Solution I figured prometaphase, metaphase and anaphase. I know...