26

Yes, there is a scientific basis, but I think you can't do anything with the apparatus shown in the figure. Here you can find much information about it. I will try to summarize. It seems that extracting coffee at a lower temperature makes it tastes better. Gale thinks that the amount of quinic acid is the key variable that makes good coffee. In fact, some ...


24

Measure the change in mass over time of the remaining liquid. Though some water will also evaporate, you can control for that by keeping the humidity near 100%. If you have to be precise, collect the outgassed $\ce{CO2}$ in a liquid-nitrogen cold trap. Check the mass of the condensate, which should equal that lost from the soda. Check purity, to be really ...


24

Inflate balloons, and tie them «at their stem» like a bouquet of flowers. If you take four of them, not too much inflated, you well demonstrate a situation close to $sp^3$ hybridization. These models equally work well in larger lecture halls by the way, and intentionally using different colors allows many options. (source) (screen photo You need some ...


23

Actually it is saponification. Bleach has alkali added to it, to stabilize it against decomposion to chlorine gas. To wash your hands after contact with bleach was a wise move.


22

Chemistry needs a devoting reader. You should try to love chemistry as much as you want! That'll be the ignition for lots of reading and stuff. My pointers: Love chemistry. Learn in an organized matter. (For example, do not jump from studying about covalent bonds' basics to reaction mechanism. Take notes of the most important points of what you learn. Look ...


22

This is actually related to the thermite reaction, where the rust on the balls reacts with the pure aluminum in the foil. Here is a pdf detailing the experiment. The activation energy for the reaction is reached through the friction and pressure, and the rust on the balls is actually very important, since it is the exchange of oxygen between the iron oxide ...


22

Yes, based on what we can see in the video, your guess appears to be correct: as the propane-filled bottle warmed up, just enough propane evaporated to keep the pressure inside the bottle equal to the equilibrium vapor pressure of the liquid propane. According to the video, the ambient temperature outside at the time it was recorded was "about 45 °...


21

There's a very simple test for $\ce{D_{2}O}$ that springs to mind - ice cubes made with heavy water sink in light water. I assume you're talking about differentiating a glass of essentially pure heavy water from, say, tap water, in which case this test should work rather well and requires equipment no more sophisticated than a freezer, ice cube tray and some ...


21

The raisin has nucleation sites on it that allow bubbles of $\ce{CO2}$ to form. The raisin is light enough to be lifted by the bubbles as they push their way to the surface. As the bubbles are released into the atmosphere, the raisin once again sinks until more bubbles form on it. This will continue until the soda water has lost the majority of its dissolved ...


20

I sympathize with your desire to launch an action figure. However, the chemistry you propose is really dangerous. You would be better off with black-powder based rockets. Is there any way to synthesize hydrazine with bleach and ammonia? Do not do this. My answer is not "yes" or "no". My answer is Don't. Do not try this without proper safety equipment ...


20

Maybe it needs to be clarified that the salt of a strong base and a weak acid can conduct saponification. Therefore the fact that bleach reacts with fatty acids creating soap, does not necessarily mean that bleach should be all just base (nor that something else other than saponification should be happening). Household bleach is mainly sodium hypochlorite (...


18

Quoting a reddit post from chemist nallen: The short answer is that the dirt and oils from your hair compete for the surfactants making them less available to form lather, which is small bubbles. To better understand the mode of action, you have to know a bit about the formulation of shampoos and the nature of dirt and oils. Dirts and oils deposit on hair ...


17

First, let me say that I've enjoyed many times exploding soap bubbles of about one milliliter filled with hydrolysis gas. That is 1 cubic centimeter. That will give you a sound that rings in your ears in a decent sized living room. You may wish to use ear protection for the experiment. 50 ml will have an effect in a lecture hall that not only wakes up ...


16

In a lemon battery, the zinc from the galvanized nail is giving up electrons and transitioning into an aqueous state: $$\ce{Zn → Zn^2+ + 2e−}$$ While zinc is entering the electrolyte, two positively charged hydrogen ions ($\ce{H+}$) from the citric acid with two electrons at the copper electrode's surface and form an uncharged hydrogen molecule $\ce{H2}$: ...


15

Of course, you’ll want to prevent a spillage as well as possible (making sure the bottle doesn’t fall over etc.) but sometimes you just run into bad luck. Let’s hope that your work bench is at least capable of withstanding the acid for a minute or two — if you have a tiled working surface that would be preferred since they will almost certainly withstand. ...


14

The froth has little or no effect on the detergent action. In fact detergent manufacturers have to add anti-foaming agents to stop excessive foam generation in automatic washing machines. Froth/foam is generated because surfactants in the detergent adsorb at the air water interface and stop the water film that makes up the walls of the bubbles from ...


14

To answer the question, let us understand sparkler chemistry. A sparkler consists of: An oxidizer: potassium nitrate or potassium chlorate. They burn off a mixture and are part of oxidation-reduction reaction: $$ \begin{align} \ce{\underset{potassium nitrate}{2 KNO3 (s)} &-> \underset{potassium nitrite}{2 KNO2 (s)} + O2 (g)}\\ \ce{\underset{potassium ...


14

What would happen if we threw the sparkler into the water? Would it keep burning under water. Most likely, not. Water is an effective coolant, so a wet sparkler wouldn't be able to propagate a burn front. Pyrotechnic compositions often severely degrade in a wet air (some might self-ignite and some might loose the ability to burn). Are children's ...


13

Wikipedia already offers a decent summary of two theories of shear thickening behavior - namely the generation of transient 'defects' in a high-density suspension that either resist further growth or are incompressible in the direction of shear. A potential macroscale analogue of shear thickening is the dramatic increase in viscosity of large particle-air ...


13

The wax doesn't need to become gaseous to cause the column of flame (if that's what you were thinking). Water, when in contact with the liquid wax at a couple of hundred degrees above its boiling point, will flash-boil in a very chaotic manner as if it were "exploding" ("transition boiling" in this graph). The water closest to the wax very quickly vaporises ...


13

In pyrotechnics, $\ce{NaNO3}$ is normally avoided because it is very hygroscopic. With dried $\ce{NaNO3}$, the effect should be identical. In any case, the usual safety rules apply!


13

Obsidian This is a volcanic glass, formed when rhyolitic lavas cool too quickly for crystals to form. From a chemistry point of view, it's a mixture of silicon dioxide, aluminium oxide, with sodium ,potassium, calcium and iron oxides in various quantities. These lavas will also contain significant volatiles (water and $\ce{CO2}$) held in solution by ...


13

You might try horseradish as a catalyst, rather than yeast. Use the fresh root, not the prepared sauce, and test a few different plants - some are more effective than others. Cosmetic supply stores stock 6% (20 volume) $\ce{H2O2}$, but that concentration is more likely to cause skin irritation or bleach fabrics. The most effective catalyst for decomposing $\...


13

Measure concentration in a fixed volume of air Easiest way might be to put it in a sealed impermeable bag or box and measure the CO2 concentration over time. Home hobbyists use something like the MG-811 CO2 sensor or a simple non-dispersive optical sensor and connect it to a Raspberry Pi or Arduino using an analog to digital converter chip (ADC). For (a ...


12

I conjecture that there are several things happening. Step 3: Addition of salt will melt the ice at its immediate point of contact. The string will naturally be surrounded by the highly concentrated brine (salt water). Step 4: This is enough time for the brine to get diluted, noting that there is an infinite reservoir of potential water by way of the ice ...


12

Gases are less soluble in warm water than cold water. The bubbles are likely from dissolved gas coming out of solution as the water warmed. The bubbles are unrelated to self-ionization of water. The self-ionization does vary somewhat with pressure, so at an extreme depth in the ocean you might need to consider what Kw is, but not in a glass of water. ...


12

During pyrolysis, organic compounds are thermally decomposed in the absence of oxygen. The pyrolysis products are classified into categories based on their physical state of existence: char (solid), bio-oil (liquid) and non-condensable gases (gas). The relative proportions of these three product fractions significantly vary depending upon the process ...


12

The person in the video said it was about $\pu{45^oF}$. At this temperature propane has a vapor pressure of about 8 atm, so that is the pressure that built up inside the Coke bottle. Once this pressure had built up, it quit boiling. The fact that he could still fairly easily squeeze the bottle suggests that it was probably not very close to bursting from ...


12

Some matchstick heads contain iron(III) oxide as a colorant. The yellowish color of the burning match indicates that it has low oxygen, i.e. a reducing flame. It reduces the iron oxide to iron which is attracted by the magnet. The reduction reactions that occur are probably quite complex. Below are two simplified possible reaction equations. $\ce{(CH2)_n}$ ...


12

This one is inspired by ideas from Ed V and Todd Minehardt. The cool thing is that the angles are pretty accurate if the chop sticks reach into the opposite corners of the cube: As a bonus, you can make an octahedral model if you make holes in the center of each square (or slightly offset so that the chop sticks can pass in the center of the cube). The ...


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