Search found 34 matches

by Jingyao Chen 4H
Sat Nov 16, 2019 5:06 pm
Forum: Student Social/Study Group
Topic: Chemistry News
Replies: 61
Views: 37104

Re: Chemistry News

This is an interesting article. Most solids expand when they are heated. However, scandium fluoride, shrink when it is heated. This is because even though the bonds are stable, the fluoride atoms are free to move a bit. This mix of rigidity causes the crystal to buckle. Here’s the link: https://www....
by Jingyao Chen 4H
Sat Nov 16, 2019 5:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Symmetry and Polarity
Replies: 13
Views: 46

Re: Symmetry and Polarity

Symmetry in the Lewis dot structure could indicate that it’s also symmetric when it is in 3D, but I would recommend just draw out the 3-dimensional figure and determine polarity based off of that.
by Jingyao Chen 4H
Sat Nov 16, 2019 4:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent or Angular
Replies: 13
Views: 51

Re: Bent or Angular

They should be the same thing. I recommend that one the test, the safest way is to use the name that Dr. Lavelle uses in lecture slides.
by Jingyao Chen 4H
Sat Nov 16, 2019 4:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs. Nonpolar
Replies: 12
Views: 46

Re: Polar vs. Nonpolar

A thing to remember is that there are polarity between bonds, and there’s also polarity of the overall molecule. Bonds could be polar, but in certain cases, because the molecule is symmetric, the overall molecule is not polar. Symmetry and the overall 3D shape is the thing that you should base off p...
by Jingyao Chen 4H
Sat Nov 16, 2019 4:53 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Ion Dipole v. Ion Induced Dipole
Replies: 1
Views: 13

Ion Dipole v. Ion Induced Dipole

I know we didn’t really go over ion dipole and ion induced dipole in class. However, I noticed that there’s also an intermolecular force called ion induced dipole. What is the difference between ion dipole forces and ion induced dipole forces? Is it similar to dipole induced dipole in the sense that...
by Jingyao Chen 4H
Sun Nov 10, 2019 1:50 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: H20 and H2S melting/boiling point
Replies: 4
Views: 16

Re: H20 and H2S melting/boiling point

Melting/boiling point depends on intermolecular forces. The stronger the forces, the higher the melting and boiling point. The reason that number of electrons and size matters is because larger molecules and more number of electrons contribute to higher LDF, which is still going back to LDF. Even th...
by Jingyao Chen 4H
Sun Nov 10, 2019 1:44 pm
Forum: Bond Lengths & Energies
Topic: how to determine the energy of a bond
Replies: 6
Views: 28

Re: how to determine the energy of a bond

The energy of a bond that you are referring is probably the energy it takes to break a bond. In the very beginning, these values are experimentally observed. To calculate it, there is a formula: delta G = delta H - T*delta S, which we haven’t learned yet.
by Jingyao Chen 4H
Sun Nov 10, 2019 1:38 pm
Forum: Bond Lengths & Energies
Topic: Strongest Bond
Replies: 15
Views: 54

Re: Strongest Bond

Intramolecular forces/bonds will always be stronger than intermolecular forces. For intramolecular forces, a good way to remember covalent bond is the strongest is to think that they are sharing electrons.
by Jingyao Chen 4H
Sun Nov 10, 2019 1:35 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: determining what force it is
Replies: 2
Views: 25

Re: determining what force it is

The answer above did a really good job answering the question. Just to add on, LDF is present in any molecules. This is the force that every molecule has, so don’t forget that when answering questions. Moreover, just a reminder that LDF is an very important force for molecules with large amounts of ...
by Jingyao Chen 4H
Sun Nov 10, 2019 1:32 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Is there a difference between Van der Waals and LDF?
Replies: 5
Views: 25

Re: Is there a difference between Van der Waals and LDF?

Van der Waal Forces include dipole-dipole forces and LDF. In the lecture notes, however, Van der Waal is written as another name for LDF. I would recommend just use the name LDF when you are referring to the induced dipole moments between molecules.
by Jingyao Chen 4H
Thu Oct 31, 2019 10:51 pm
Forum: Bond Lengths & Energies
Topic: Double bond vs single bonds
Replies: 4
Views: 22

Re: Double bond vs single bonds

For double bonds, two pairs of electrons are sharing, instead of one pair. Therefore, the bond is stronger, and therefore makes the two atoms closer to each other. Double bonds take more energy to break than single bonds.
by Jingyao Chen 4H
Thu Oct 31, 2019 10:49 pm
Forum: Electronegativity
Topic: Polarity
Replies: 5
Views: 27

Re: Polarity

It is correlated in someone. Polarity can be referred to in terms of bonds and in terms of a molecule as a whole. Within a bond, as long as the electronegativity of the two atoms are not the same, the result is a polar bond (unequal sharing of elections). In the context of a molecule, however, it’s ...
by Jingyao Chen 4H
Thu Oct 31, 2019 10:47 pm
Forum: Ionic & Covalent Bonds
Topic: Radicals
Replies: 9
Views: 42

Re: Radicals

Adding on, free radicals is one of the theory regarding human aging. Some people believes that because of these free radicals that go around and damage cellular contents, the resulting consequence is the process of human aging.
by Jingyao Chen 4H
Thu Oct 31, 2019 9:52 pm
Forum: Student Social/Study Group
Topic: Chemistry News
Replies: 61
Views: 37104

Re: Chemistry News

This is a very interesting and exciting news! A catalyst consisted of platinum nanoparticles is able to cleave plastic’s carbon to carbon bond to produce liquid hydrocarbon, which could be further used to do a lot of work.
https://www.sciencedaily.com/releases/2 ... 075131.htm
by Jingyao Chen 4H
Thu Oct 31, 2019 9:46 pm
Forum: Bond Lengths & Energies
Topic: Intermolecular forces
Replies: 3
Views: 277

Re: Intermolecular forces

Bond length refers to intramolecular forces, such as ionic bonding and covalent bonding. These intramolecular forces result in the formation of molecules and compound. The attractions between these molecules and compounds are intermolecular forces.
by Jingyao Chen 4H
Thu Oct 24, 2019 9:38 pm
Forum: Electronegativity
Topic: Trend of Electronegativity
Replies: 18
Views: 608

Re: Trend of Electronegativity

An easy way to remember the trend of electronegativity is to think about the concept of electronegativity. Electronegativity is the tendency to grab electrons. The atoms on the right side of the periodic table want to grab electrons to reach octet. Therefore, the electronegativity increases as you m...
by Jingyao Chen 4H
Thu Oct 24, 2019 9:15 pm
Forum: Ionic & Covalent Bonds
Topic: Resonance
Replies: 12
Views: 76

Re: Resonance

Because electrons occupy greater volume, which means less repulsions, and therefore more stability.
by Jingyao Chen 4H
Thu Oct 24, 2019 9:12 pm
Forum: Ionic & Covalent Bonds
Topic: Cation
Replies: 23
Views: 113

Re: Cation

Cations are ions that gets electrons stripped away. They lose electrons to reach octet to become more stable. On the contrary, anions likes to gain electrons to reach octet and become more stable. They are important because after ions are formed, ionic bonding can form.
by Jingyao Chen 4H
Thu Oct 24, 2019 9:00 pm
Forum: Ionic & Covalent Bonds
Topic: HW 2A#5 part a
Replies: 2
Views: 29

Re: HW 2A#5 part a

During the lecture, copper is one of the exceptions. The electron from 4s2 moves to the e energy level because it’s more stable. Therefore, when one electron is needed to be removed, it is moved from the 4s1 level. Cr is also the other exception.
by Jingyao Chen 4H
Thu Oct 24, 2019 8:49 pm
Forum: Ionic & Covalent Bonds
Topic: valence electrons
Replies: 6
Views: 49

Re: valence electrons

The electrons in 5s and 5p are in a high energy level than 4d. Therefore, valence electrons, and the electrons that gets stepped away first are in 5s and 5p.
by Jingyao Chen 4H
Thu Oct 17, 2019 10:29 am
Forum: General Science Questions
Topic: Periodic Table
Replies: 5
Views: 50

Re: Periodic Table

Yes, we will be given a periodic table and most of the formulas on tests.
by Jingyao Chen 4H
Thu Oct 17, 2019 10:28 am
Forum: General Science Questions
Topic: Periodic Table
Replies: 5
Views: 50

Re: Periodic Table

I believe it is just the next decimal place of the molar mass. It could be that we don’t need to go that far for using molar mass, but just for your information, the next decimal place is there.
by Jingyao Chen 4H
Thu Oct 17, 2019 10:20 am
Forum: Photoelectric Effect
Topic: Speed of Light
Replies: 29
Views: 115

Re: Speed of Light

Yes. It is a constant and is universally agreed/defined as the length traveled by light in a vacuum condition in ​1⁄299792458 seconds.
by Jingyao Chen 4H
Thu Oct 17, 2019 10:14 am
Forum: Photoelectric Effect
Topic: Particle vs. Wave Model
Replies: 5
Views: 27

Re: Particle vs. Wave Model

Yes. Photons and electrons have both particle and wave light properties. They behave like waves together in a group. Moreover, based on the wave-particle duality, large objects have wave properties as well. However, this can’t really be proved because it’s hard to observe=serve, based in their large...
by Jingyao Chen 4H
Thu Oct 17, 2019 9:56 am
Forum: Photoelectric Effect
Topic: Confusion on equations
Replies: 9
Views: 94

Re: Confusion on equations

For these equations, the E in the equations are all energy for the energy of a photon, so the equations are interchangeable because they apply to the same thing. Therefore, you can decide which equation to use based on the variables you are given and the variables that you want to solve.
by Jingyao Chen 4H
Thu Oct 10, 2019 8:58 pm
Forum: Student Social/Study Group
Topic: Chemistry News
Replies: 61
Views: 37104

Re: Chemistry News

https://www.scientificamerican.com/article/how-do-the-chemicals-in-sunscreen-protect-our-skin-from-damage/ This article talks about uv’s damage on the skin and the mechanism of sunscreen. When UV shines on skin, it excites photons. When the electron falls, it releases energy which promotes biologica...
by Jingyao Chen 4H
Thu Oct 10, 2019 8:45 pm
Forum: Student Social/Study Group
Topic: Chemistry News
Replies: 61
Views: 37104

Re: Chemistry News

A research has shown that students who had protein drinks actually done better than students on caffeine! So next time when you want to study, try grab protein drinks, not coffee! :)
by Jingyao Chen 4H
Thu Oct 10, 2019 8:43 pm
Forum: Student Social/Study Group
Topic: Chemistry News
Replies: 61
Views: 37104

Re: Chemistry News

I’ve learned from my cluster professor today that when you drink coffee, the milk in the coffee actually has opposite effects, because the milk protein is sticky and binds to a lot of different things. So next time, when you want to drink coffee, go without milk or with soy milk! :)
by Jingyao Chen 4H
Thu Oct 10, 2019 8:33 pm
Forum: General Science Questions
Topic: temperature
Replies: 4
Views: 54

Re: temperature

I’m not a hundred percent sure if they will be on the test, but I feel like you should just try to learnt he conversions as early as possible :)
A lot of the future chemistry problems involve conversions, especially in thermodynamics.
by Jingyao Chen 4H
Thu Oct 10, 2019 8:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 209
Views: 101126

Re: Saying Thank You to Dr. Lavelle

Thank you Dr. Lavelle for making the concepts super easy to understand. You are a wonderful teacher. With your lectures, I was able to grasp new concepts in a very short amount of time. Thank you!
by Jingyao Chen 4H
Thu Oct 03, 2019 11:09 pm
Forum: General Science Questions
Topic: Can We Take The Final In Pencil?
Replies: 14
Views: 465

Re: Can We Take The Final In Pencil?

Thank you all for this info! Maybe I should practice doing homework with pen.
by Jingyao Chen 4H
Thu Oct 03, 2019 11:06 pm
Forum: General Science Questions
Topic: Rusty on High School Chem [ENDORSED]
Replies: 166
Views: 100953

Re: Rusty on High School Chem [ENDORSED]

I’m currently in the same situation as you. One suggestion adding on to all the ones above would be trying to forget the fact that you’ve learned chemistry in high school. When I think that I’ve taken AP chem and have received a good score, I might not be as focused in lectures because I think that ...
by Jingyao Chen 4H
Thu Oct 03, 2019 8:57 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 139
Views: 84005

Re: Advice from a Medical Student [ENDORSED]

Thank you so much for sharing this! I have just began this course, and I will make sure to follow your advice. Thank you!
by Jingyao Chen 4H
Thu Oct 03, 2019 8:54 pm
Forum: Balancing Chemical Reactions
Topic: Question L.35 [ENDORSED]
Replies: 6
Views: 79

Re: Question L.35 [ENDORSED]

For the rest of the problem, you can see that from all of the balanced equations, for every 8NaBr to be produced, 3Fe is needed. You can then start with the dimensional analysis. First convert the ton of NaBr to grams, then use molar mass to get the number of moles in 2.5ton of NaBr. Then you can us...

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