Questions tagged [teaching-lab]

For questions regarding teaching in a laboratory setting.

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0answers
44 views

Why do we begin an experiment involving solutions of different concentration from the least concentrated solution?

Is there a particular benefit to start any kind of measurement with the least concentrated solution and then work my way up to the more concentrated solution? In one of my experiment, we measure the ...
2
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1answer
147 views

Why does camphor sublimate?

I was doing a laboratory experiment the other day and they asked us to heat a beaker that contained camphor and to cover it with a watch glass with ice on it. I understand the crystallization ...
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1answer
52 views

Is it possible to make polyethylene in a high school laboratory?

We learned how to make small amounts of ethene from ethanol using sulfuric acid. Is there a way to make a visible amount of polyethylene from that using materials I could get for a school lab? We can'...
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1answer
140 views

How to effectively wash the precipitate or crystals on the filter and why?

My lab manual says that the precipitation on filter should be washed with a few small portions of the washing liquid. Why can't I just completely fill the filter funnel with the solvent instead of ...
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0answers
42 views

Limiting factor on Belousov-Zhabotinsky reaction

In the thin film Belousov-Zhabotinsky reactions (popular on Youtube/in chemistry demonstrations), concentric rings of different colors propagate across a petri dish for minutes to hours as the ...
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1answer
41 views

Are the words “apparatus” and “equipment” synonyms? [closed]

Are the terms "apparatus" and "equipment" synonyms, within a chemistry or physics laboratory? If not, what are distinguishing factors?
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3answers
1k views

Should data tables be made in pen or pencil? [closed]

For a chemistry lab, I have to make a data table. Should data tables be written in pen or pencil? What is done in the real world of Chemists and why is it done in such a way?
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1answer
2k views

Making nylon experiment - Questions

I made nylon in a lab with these procedures - 1) Collect 30mL of sebacoyl Chloride dissolved in hexane 2) collect 30mL of 1,6-hexanediamine dissolved in water . 3) Transfer the beaker containing ...
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0answers
106 views

Wondering how I should have graded this question (freshman lab, about buffer capacity)

I TA the intro freshman lab course. In a lab about buffers and buffer capacity, the students were instructed to make 50 mL of a 0.1 total molar pH 6.70 buffer by dissolving solid $ KH_2PO_4 $ and $ ...
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2answers
9k views

Why bother to standardize a solution?

I have been preparing lessons for some of my students about preparing acidic and basic solutions, and I keep finding pre-made labs in which the students "standardize a basic solution" by titrating it ...
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1answer
459 views

How to remove hydrate from Fe(NO3)3 . 9H2O?

I am currently in a dilemma where I need to have pure Iron (III) nitrate, but I have Iron (III) nitrate 9 hydrate in order to do a lab experiment where I investigate voltaic cell. I am pretty sure the ...
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1answer
412 views

What will Happen if p-nitrophenol is heated with HCl and then cooled?

When working in my Lab with p-nitrophenol ,I added some concentrated HCl and heated until it was fully dissolved. Then I cooled it in ice bath and found a white salt like compound which is not ...
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1answer
2k views

How to remove sulfuric acid from sample

I have problem with my experiment. My experiment is acid hydrolysis of ethyl benzoate. The acid that I used is sulfuric acid. My problem is when I get the precipitate (impure benzoic acid) I have to ...
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1answer
540 views

What is a laboratory set-up for the synthesis of ethanol from ethene?

I am doing a chemistry investigation and one component of that requires me to synthesize ethanol from ethene. Ethene itself is gaseous at room temperature and pressure so I was wondering if someone ...
7
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1answer
96 views

What is the standard way of reporting/interpreting measurement uncertainty in scientific publications?

As an undergraduate student I was often told in lab classes to report every single measured or calculated quantity with its associated uncertainty in lab classes, in the form $(10.1 \pm 0.1 )~\mathrm{...
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4answers
7k views

How are solvents chosen in organic reactions?

Just reading through organic chemistry book (Modern Projects in Organic Chemistry by Mohrig, et al.), and it seems like the choice of solvent is usually arbitrary. One of the experiments designed ...
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0answers
228 views

How does toluene favor ortho/para in terms of kinetic and thermodynamic control?

If nitration of toluene is carried out at a very low temperature, presumably the reaction would be carried out under kinetic control. During these conditions that favor kinetic products, is more ortho ...
4
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1answer
858 views

Are there any common and identifiable hazards to being a Chemistry Teacher? [closed]

I'm a High School Chemistry teacher. I have only been teaching for a few years and know very few other chemistry teachers. Of the ones I do, One has died of cancer, one is a cancer survivor and one is ...
6
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3answers
25k views

What's the difference between pipettes calibrated “TD”, “TC”, “Blow-out” and related terms?

I've never blown-out the last drop of any glass pipette I've ever used during my undergraduate studies. Recently I re-read some notes I had lying around in order to prepare a class I had to give to a ...
6
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1answer
3k views

Concentration of NaOH to dissolve glass

I am doing a physics experiment in which it is required to etch the outermost glass layer from a coverslip (regular lab apparatus). What concentration of NaOH should be dissolved in water, and how ...
6
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2answers
1k views

Is sulfide ion a stronger base than hydroxide ion?

I received these three responses. They are all, except the last response, incorrect to varying degrees. I am, however, unsure about how to grade these responses because the question itself, in my ...
7
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1answer
288 views

What's the reaction here?

I have found a gif photo on the internet and I am very curious what is happening there? What reaction is the reason for that?
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2answers
89 views

Calcium chloride hexahydrate has separated in jar - is it beyond saving?

I work in a lab where I'm in charge of ordering new supplies. A graduate student brought up a $500~\mathrm{g}$ amber jar of $\ce{CaCl2.6H2O}$ and pointed out that it had separated into a clear liquid (...
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3answers
716 views

Teaching: Two elements that make XY2 and XY4 molecules

I am not a chemist, but I will be explaining chemistry to some third-graders. I want to give the example of how different things can be made of the same parts, but arranged differently. My "real world"...
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0answers
52 views

Is there a generic graphical language to represent chemical reactions?

I want to show a schematic representation of chemical reactions from start to finish in a way that will include more detailed preparation instructions than a plain chemical formula: volumes, ...
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2answers
2k views

Why does zinc plate copper in silver penny lab

In class, we performed a lab that involved heating a solution of zinc sulfate with zinc strips at the bottom of the beaker. A penny was placed on top of the zinc strips and soon after the penny became ...
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3answers
2k views

Lab safety - Long vs. Short Sleeves on Lab Coats

I have three lab coats, two with long sleeves, and one with short sleeves. I saw that the concepts about lab safety vary from country to country; in some places it looks like the short-sleeve coat ...
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1answer
2k views

How can an inexperienced chemist determine the chemical structure of a molecule?

I'm a fairly inexperienced, but nonetheless interested chemist, currently planning a small project for the coming summer: I want to isolate an unknown chemical from a plant and determine it's chemical ...
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1answer
4k views

Why might the O—H stretch in the IR of MY triphenylmethanol product be less intense than expected?

Why might the O—H stretch in the IR of MY triphenylmethanol product be less intense than expected when compared to the expected IR for triphenylmethanol? I'm interpreting the IR I took of my product, ...
6
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1answer
1k views

Possible Synthesis of MVK from 2-Butanone?

My professor wanted me to set up a lab to synthesize Methyl Vinyl Ketone (AKA Butenone) from some MEK we have lying around (2-Butanone). Now, I know there are multiple ways to do this, but the tricky ...
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4answers
660 views

How much does the quality of glassware matter, really?

Discussing about the pros and cons of glassware from different manufacturers for chemistry experiments easily becomes a heated debate. Well, that's how it seems if you read the chemistry related blogs,...
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2answers
2k views

In which country is it allowed to practice non-clandestine amateur chemistry? [closed]

I travel a bit so am flexible where I live, and have taken a recent interest in chemistry to try to gain an understanding of physical reality. I find learning from textbooks to be good, but want to ...
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1answer
2k views

Creation and Combustion of Nitrocellulose

I am intending to demonstrate the formation and combustion of nitrocellulose with my high school students, however I am concerned about the potential products of the combustion equation. I have been ...
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1answer
1k views

How to make 0.3% ammonia water from 28-30% ammonia hydroxide

Can someone tell me how to make 0.3% ammonia water from 28-30% Ammonia hydroxide? I am trying to make a gallon or 3.78 Liters.
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1answer
245 views

Why isn't hybridization done in America? [closed]

Warning: This is a question from my teacher. In America hybridization isn't done, while in Europe it is done around the 10th grade. Is there any reason or advantage for doing(not doing) it as part of ...
4
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1answer
3k views

How to interpret the instruction of the dilution of hydrogen peroxide?

I am required to prepare $\pu{120cm3}$ of hydrogen peroxide to each of one of my students tomorrow. Some material is given to me on the method of preparing the solutions. Within the method of ...
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4answers
11k views

Safe explosion demonstrations

As an end of high school treat, my class is trying to convince our chemistry teacher to make an explosion as a demonstration. What sort of reactions are beautifully explosive but safe enough to do in ...
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1answer
7k views

Distillation: Simple vs Fractional

Here is the excerpt of my lab manual: "Simple distillation is more useful for purifying a liquid that contains either a non-volatile impurity or small amounts of higher or lower boiling impurities. ...
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1answer
770 views

TLC: Why is a more polar eluent more effective at displacing the points?

If the points are non-polar, I don't see how making the eluent more polar will make them travel faster. Anybody care to explain?
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1answer
4k views

Under what circumstances is working in the chemistry lab hazardous to health in the long term? [closed]

I would like to know when working in the Chemistry lab would be hazardous to health in the long term. Because as everyone who worked in the chemistry lab knows that they would be handling many ...
3
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3answers
552 views

Explaining redox reactions to a 6 year old?

In a similar vein and for pretty much the same reason as I post this question on the Physics.SE site, what would be a an effective means to promote understanding about redox reactions to a 6 year old? ...
0
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1answer
93 views

Acid-base reaction is screwing up my synthesis

I'm gonna get kicked all the way to the Moon, but whatever. I am doing some nitroglycerin. I know the process, since the reaction itself is pretty basic. I know that it is an electrophilic ...
8
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3answers
1k views

What is the correct name for this lab technique in crystallization?

Take a glass rod and rub vigorously the wall of the flask, the substance will crystallize out of the solution. Take a fire polished stirring rod and etch (scratch) the glass of your beaker. The small ...
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3answers
2k views

67 failures at extracting acetaminophen from Excedrin(R)

I have adapted the lab experiment described in this J. Chem. Ed. article for the organic chemistry lab course I teach. In the past year, the first year of implementation, I have had 67 failures (100% ...