Formation Definition and 480 Threads

Homework Statement A tank of water has been outdoors in cold weather, and a slab of ice 5 cm thick has formed on its surface. The air above the ice is -10C. Calculate the rate of ice formation ( in cm / h) on the ice slab. Take the thermal conductivity of ice to be 0.004 cal / (s.cm.C) and...

I am not very versed in physics but if it was possible to collide antimatter with antimatter would that create a black hole?

According to the History Channel documentary Comets -- Prophets of Doom (DVD), Earth today accumulates "30 to 40 thousand tons of space dust per year". CRUDE MODEL: We imagine that the accumulation rate of space debris declines exponentially: rate = T \times e^{-\frac{t}{\tau}} We then...

I have for a long time now wondered about how the planets and moons actually congealed into their current forms. How can loose mass and gas develop the gravity to pull themselves together? Could the cause of these actions been related from the "big bang" which threw out micro black holes of...

How does the temperature of a star relate to the radius of a star? How does the mass of a star affect the temperature of the star's core? How does the luminosity of a star relate to how long a star will live? How do the spectral lines of a star determine if the star is a first generation...

hi there.. is there anyone know how to synthesis an Acetylsalicylic Acid from Acetic Anhydride and Salicylic Acid . i just know how 1 step.. but then my proff told me there's suppose to be like 5 or six step to obtain it. i'll appreciate your response.

Hi everyone! My first post, so bear with me. I have a query that I didn't quite know who to ask about, and came across this site, so I hope this is the right place to put it. My cat's bowl was left (empty) on the verandah and got caught in the rain yesterday afternoon. Overnight...

Homework Statement The problem statement is to find the heat of formation of NH4CL using the calculated variables and two more reactions. If I calculated it correctly the HF for ammonia plus hydrochloric acid to be -247.7kj/mol. I am not sure what else it is that I need to do...

[9] arXiv:0809.2330 [pdf, other] Title: Hydrodynamics of structure formation in the early Universe Authors: C. H. Gibson (UCSD), T. M. Nieuwenhuizen (University of Amsterdam), R. E Schild (Harvard) Comments: 6 pages 4 figures. Additional information at this http URL Subjects...

This paper makes the case for an upper mass limit of about 10 billion solar, for black holes. Their central black holes may help galaxies to form and may be important to understanding structure formation---an outstanding problem in cosmology. The mass limit is proposed tentatively and requires...

Structure formation is arguably the central problem in cosmology. How did the dilute gas manage to coagulate. On what timetable did stars and galaxies form? What explains the distribution of galaxy sizes and composition--clustering--the wispy cobwebby structure with its various size voids...

http://blackholes.stardate.org/resources/articles/article.php?id=9 This presupposes that dark matter and dark energy interactions play no role?

When things are kept at the simplest, I've heard that galaxies were formed because gravity pulls stuff together, but there's some things that are not fully making sense. If two objects are far away, and they get attracted by gravity, what happens is that they merely pass each others with some...

http://space.newscientist.com/article/dn14435-universes-first-stars-bulk-up-in-new-simulation.html The new computer simulation study suggests that early stars tended to be quite large, order of 100 solar masses, implying short life. The possibility is mentioned that the James Webb telescope...

Hi folks, I've recently been studying point defects, but I can't seem to come across how the formation of f-centres actually affects the density of a crystal. Does it increase or decrease the density? Thanks for any help/ ponters

I think this question was addressed many times in the literature but I was not able to make a clear picture for an answer. It is known that peculiar velocities of galaxies are too small to explain the formation of voids. Voids must have existed already before galaxies were in place with their...

When our star the Sun finally accumulated enough matter for fusion to start what would that have done to the planets around it? Afterward what would have happened to the Earth for it to get from when the sun started fusion and blasted the Earth and now, with water and atmosphere?

Homework Statement I'm interested to know how cooper pairs are formed in low temperature superconductors. The Attempt at a Solution My basic understanding is that electrons will repel other electrons and attract the positive ions which make up the lattice of the metal. The attraction...

1. An object is placed in front of a converging lens in such a position that the lens (f = 11.0 cm) creates a real image located 27.0 cm from the lens. Then, with the object remaining in place, the lens is replaced with another converging lens (f = 19.0 cm). A new, real image is formed. What is...

Homework Statement The diagrams below illustrate the formation of a rainbow. Figure 1 shows the general arrangement and Figure 2 shows the path of a ray through a raindrop with the centre of the raindrop is labelled O. Figure 1: Figure 2: a.) Where the ray enters the raindrop in...

Homework Statement This is a question from a sample exam that I can't figure out. The answer is 1297 kJ/mol, but I don't know how to solve it. Any help is appreciated. ----- The following are average bond energies (kJ/mol): C−H 413 O−H 463 C=C 614 C−C 348 O−O 146 C=O 799...

[Sorry about the long post] I'm doing an essay where I am exploring whether or not elements were, for the most part, formed under conditions of thermodynamic equilibrium. We know that some element clearly aren't (such as Potassium 40 and uranium which decay radioactivly). I've scoured the web...

[SOLVED] free energy of formation Homework Statement Consider the reaction 2NH3(g) --> N2(g) + 3H2(g) If the standard molar free energy of formation of NH3(g) at 298 K is –16.45 kJ·mol–1, calculate the equilibrium constant for this reaction at 298 K. The correct answer is 1.71E-6...

Homework Statement This is not a problem, per se, because it is part of my Lab. We're calculating the standard enthalpy change of formation for solid Ammonium Chloride. To do this, we're using four separate rxns, and totaling their individual standard enthalpy change of formations. For two...

Acetanilide synthesis HCl, aniline, sodium acetate trihydrate=> Acetanilide I'm being told that there is an intermediate formed (anilinium hydrochloride) but I can't figure out how it is formed exactly. (Is the reaction, for the anilinium hydrochloride just the aniline attacking a H-Cl...

. They understand the classical Schwarzschild radius argument for black hole formation. They have bare rudiments of special and general rel. I sound like an idiot saying "there's this anti-gravity" force that kicks in when the collapsing system gets really big. Any help?

Can anyone solve me these questions, please 1. A convergent lens has one 8 cm focal length. One places a 2 cm height object at 4 cm of his optical center. Find the various characteristics of the image obtained. 2. A divergent lens has one 8 cm focal length. One places a 2 cm height object...

Hi, I'm not good enough to contribute answers yet, but I hope to entertain you with questions. Practically all the Earth formation stuff I've read talks about the Earth being molton. That always seems strange to me. If I think of a space body without an atmosphere, I generally think of it...

There is a bit of data and literature that shows the standard heats of formation for various uranium compounds including UO3, U3O8 UF6 etc. However there appears to be nothing on ammonium diuranate which is one of the most common intermediate forms produced by precipitation. The ADU as it is...

Homework Statement A 75 g bungee cord has an equilibrium length of 1.20 m. The cord is stretched to a length of 1.80 m, then vibrated at 20 Hz. This produces a standing wave with two antinodes. Homework Equations I really am not sure how to approach this using an equation, tried to use...

Currently I am enrolled in college level General Chemistry course, and at this time we are working on a project to figure out the delta heat for formation of a specific reaction. The equation is this H2 + CuSO4(aq) ---> Cu(s) + H2SO4. We have gone through and determined the half...

What is the estimated value of the local star formation rate (SFR) and how accurately do we know this number?

Calculate the energy change for the formation of CaF2 (s) from its elements in their standard states and the following information: Ca (s) + F2 (g) -> CaF2 ? Ca (s) -> Ca (g) = 179.3 kJ/mol Ca (g) -> Ca+ (ion) (g) + e- = 589.9 kJ/mol Ca+ (ion) (g) -> Ca2+ (ion) (g) +e- = 1145 kJ/mol 1/2...

I realize that this is a chem prob, but I'm stuck with what I thought was a straightforward problem while studying for my physical chemistry exam. Homework Statement The standard molar enthalpy of combustion of solid phenol (C6H5OH) is -3054 kJ/mol at 298k and it's standard molar entropy...

A friend and colleague found a fossil and brought it into show me. It is a small leaf in a rock. He asked me how the rock was formed, but I couldn't say as I know nothing of such things. The rock is layered. You can see the various layers by looking at the rock edgewise. In fact, the edge is so...

My question is about the formation of a neutron star once fussion stops and it collapses. I recently saw a show about the life of a star and it said when gravity overcomes the energy released by fussion, the electrons are compressed toward the nucleus of the atoms and create neutrons. I...

What causes objects (such as leaves) in the pool to group at the edges?

The question I'm about to asked has probably asked before many times b , but I keyed in a "supermassive black holes and galaxy formation" in the PF search engine , and this question has yet to be asked: How can supermassive black holes be aid the formation of galaxies when they are suppose to...

Homework Statement Find the average bond enthalpy, εN-F, for NF3(g)→ N(g) + 3F(g) Heats of formation NF3(g)→ 1/2N2(g) + 3/2F2(g) -∆ƒHºm = 124.3 kj/mol 1/2 F2(g) → F(g) ∆ƒHºm = 79 kj/mol 1/2N2(g) → N(g) ∆ƒHºm = 472.7 kj/mol...

Homework Statement Hi, I've worked this out (I think) but would appreciate someone xhecking over my method. U 235 and U 238 found in ratio of 7.3E-3 to 1, but thought to have been produced equally (ie equal quantities) half lives are 1.03E9 and 6.49E9 respectively. Estimate time since...

So far i have found two theorise of how they form, the SSPSF shock wave model ,and the Density wave model, or they may form by a combination of the two. As i am not sure how old these theories are, i wonder if there are any new insights on the subject?

I Need the explanation of "The image of formation of black hole" Please Explain Me This

Question Statement: Would you expect the enthalpy change of formation of calcium carbonate to be higher or lower than that of magnesium carbonate. What I think: Calcium has a bigger radius than magnesium, hence I expect the lattice energy of MgCO3 to be greater than the CaCO3. I suspect...

Homework Statement What are the physical and chemical changes that occur when NaOH and Zn react.?Also how do this reaction differ from the reaction of Zn and HCl? Homework Equations ------------------------------------------------------------------------- The Attempt at a Solution...

I was curious as to how planetary type spherical bodies form. Specifically, I was curious as to how the gravity affects the nebulous particles moving within themselves just prior to a solid planetary body forming. Is it not true that gravity is essentially zero in the center of a planetary...

If something hit the Earth billions of years ago and caused a molten blob to be released from it,and this blob settled into a spherical shape,after vibrating a lot,could the moon still be vibrating because of a formation process like this?

I am puzzled about the formation of blackbody emission (Planck's law). Specifically, we know that such things like incandescent lamps, an electric arc in a gas at high pressure etc. produce a nearly blackbody spectrum of corresponding temperature. Does this mean that in these cases a nearly...

Homework Statement i did a lab calorimeter lab with 50ml 1.51M nh3 and 50ml 1.59M hcl yeilding nh4cl (aq) the deltaT was 8.6 degC second part is 100ml of h2o and 4.082g nh4cl deltaT was -2.8 degC Homework Equations how do i find deltaH per mole for each reaction?The Attempt at a Solution

When hydroxide ion is added to Mn(II) in aqueous solution, an insoluble white precipitate of manganous hydroxide, Mn(OH)2, is formed. If there is oxygen present, this material reacts with it to form manganic hydroxide, Mn(OH)3 Part one was easy because it wasnt a redox it just needed to be...

In an edition of the New Scientist it says: "The streams of water vapour and ice particles that form behind an aircraft, called contrails, are known to create cirrus clouds. These clouds can trap heat radiating from the Earth's surface and thus add to global warming" How big an addition to...