Heavy Metal Contamination

Hastelloy is a common alloy that used in sewage pipe due to it's high corrosive resistance and high tensile strength. The sewage from city will flow to suburb through pipe. In the sewage, it contain a lot of chemicals that produced by citizens. With the time goes by, the impurity in the sewage will come closer together and shape precipitate attach inside the pipe. Which will jam the normal circulation of sewage. To solve this problem, people usually add some acid in the sewage to dissolve the precipitates.

Specifically, the common precipitate is CaCO₃ and the common acid used is HCl.
Chemical Equation:
2HCl(aq)+CaCO₃(solid)àH₂O(liquid)+CO₂(gas)+CaCl₂(aq)

As we see, by reacting with acid, the precipitate will decompose to CO₂ gas and soluble salt.

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However, this solution caused another unperceived problem. That is heavy metal pollution. In each joint of 2 pipes, people will use high temperature fire to burn the metal and solder them together. Notice that in the solder process, the heavy metal in the pipe will be oxides and expose outside, and directly contact with sewage. When people add acid to dissolve the precipitates, at the same time, those heavy metals will be dissolved too. They will exist in sewage flow into river and sea in form of ion and enter the recycling of nature. Fortunately, people realized that and do some change in pipe to reduce the contamination of heavy metal right now.

Check out this website for more information:
https://www.nlm.nih.gov/medlineplus/ency/article/002822.htm

Prompt#4 Scholar VS Popular

Compare to the scholar articles, the articles from blog seems more easy to understand for public. Even for me, a person in chemical field, still feel the blog is more readable.

In blog, we find that we barely see a technical term. However, in a academic essay, it has a lot of professional vocabularies. It is makes sense that when people read blog, they do not have to pause due to the professional words. And it will make the reading process smooth and fluent. About details in explanation, the scholar article will never use like personal experiences or untested things in paper. Instead, it will give you a detailed research, how it works and the outcomes. Everything in scholar article is rigorous and punctilious. Which is kind of boring for normal readers. In blog, we can use anecdotes, hilarious stories or even jokes as examples.

I think, if a person is major or want to deep in a certain area, then he or she should choose scholar sources. If a audiences just curious and not want to dig into, then the blogs or journals are enough for their demand.

Solution

Solution is some solutes dissolve in solvent uniformly. Knowing solution better is extremely important for people in chemistry filed. After all, most of experiments are happened in solution and the properties of solution will influence researcher's outcome.

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For example, if we measure the enthalpy of a certain reaction. (Definition of Enthalpy ) We should exclude the heat change happened in dissolved process, because it is not account for the heat transfer of reaction. So, to eliminate it, we cannot use the solution that just dissolved. We should wait for a moment to make sure the solution is cool down. The reason why the solute dissolve will generate the heat is because of the intermolecular forces. The energy of intermolecular forces is much less than chemical bond, but it still store some energies. So, when the substances dissolve in solvent, the forces between solute and solute need absorbs energy to push each substances away and the new intermolecular bond between solute and solvent will need release energy to form. The total energy will depend on this 2 process. So for some dissolutions, absorbed energy may more than released energy and other then vice versa.

Another interesting phenomenon is that some certain solution have unique color. It is really easy for people to differentiate the different solutions when people do not know what the solution is.

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Prompt#3 Interview with My TA

During my EGR 100 class, I was ask my teaching assistance, Chelsea, several questions:

What is the biggest misconception of an engineer?
*Doing projects all day and always talks about professional topic.

Why people will consider engineers as this way?
*Engineer for most people is kind of untouchable. It is study based on mathematics, science subject which is not required for a normal people. So, when people think about a thing that they never touched before, they always will judge them with their own thought and also follow others' idea blindly. It makes them do not know what a engineer truly is.

According to your experience, what do you think of engineers?
*It is not rigid as public thought. Sometimes, it is really fun. Like the process of figuring out problems, brainstorm with plenty of novel ideas, teamwork between teammate and so on. Sometimes, when finish a project, our engineers will feel really achievable. Especially when it accept by public and apply to life, the joyfulness is incomparable with anything else.

Prompt#2 Ethics of Chemical Engineering

Here are ethics code of chemical engineering from AlChe(America Institution of Chemical Engineering)

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• Being honest and impartial and serving with fidelity their employers, their clients, and the public;
• Striving to increase the competence and prestige of the engineering profession;
• Using their knowledge and skill for the enhancement of human welfare.

About the first code, I actually have never thought about it before. I always thought engineers just need focus on how to operate all kinds of projects and consider this ethic code as a business field code. However, after pondering, our engineers are indeed service to our employers and clients. They pay money for us. As pay back, we need satisfy their demand. Just like a equal deal. We cannot receive their money or other form of support but do nothing.

The second code I think it is obvious one. Every engineer will agree with that. Once our engineers choose enter a certain field, it means we always need work on this field and dedicate ourselves in this field. It including doing a lot of calculations, researches and tests again and again to prove the our project. As a whole, if each engineer do some contribution on his or her project, then the entire engineer filed will be promoted.

Also, the goal of us is not just to make money, we also should take consider from the human welfare aspect. In fact, our engineers constantly to enhance our human welfare. Take the most common example, cell phone. In the past, the communicate way between each person is much hard than now. People cannot contact with a person in anytime or anywhere. But now, with the development of engineering filed, especially the computer engineering filed, the popularizing rate of cell phone almost approach 100%. Besides, cell phone right now is become a part of our life, people also can treat cell phone as a entertaining device and work tool. It truly makes people's life much convenience.

Intermolecular Forces

As we all know, solid, liquid and gas are 3 common phase of all the substances. But, what factor make all the substances appearance as these 3 different states? The answer is what I am talking about today--intermolecular forces.

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First, the intermolecular forces can divided into 5 categories. They are dispersion forces, dipole-dipole forces, hydrogen bonding, iron-dipole forces and ionic bounding. If the intermolecular forces is strong enough to pull all molecules close together and shape a stable limited space with each molecules, this is what we known as solid. Oppositely, if the intermolecular forces is so weak that cannot attract each molecules together, then the molecules will separate with each other due to the repulsion and collisions. And this is what we called gases. The intermolecular forces of liquid is intervenient.

Image from: url

There are some other properties of substances relate to the intermolecular forces such as viscosity and surface tension. The viscosity will increase with stronger intermolecular forces and will decrease with weaker intermolecular forces. About surface tension, the molecular inner water can balance all the force from it's opposite directions. However, the molecules in the surface, they do not have a upward force to offset the force downward. Hence, if the weight of a lightly staff is equal to the downward force, this staff literally can stand on the water.