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Chapter Text

“Gabriel: what chemical process in animals produces carbon dioxide?” Michael asked his not-so-little-anymore brother

“Respiration. Commonly referred to as breathing, but it is the diffusion of carbon dioxide and oxygen rather than the movement of air,” Gabriel turned to Sam, sitting next to him. “What is it called when you grow plants in water instead of soil?”

“Hydroponics. Dean, what is one advantage of hydroponic farming?”

“Hydro-whatnow? Oh, hydroponic, right, uh, yeah, um… you can control the nutrients the plant receives better. Lucifer, what part of a xylem vessel provides the strength to support the plant?”

“Why would xylem need…never mind. Plants, not angels. It’s the lignin,” Lucifer looked down at the exam paper in front of him. “Okay, Raph, you need to look at the table. Advantages and disadvantages of growing cucumbers on the moon using hydroponic farming.”

“The hydroponic yield is 12-13 times that of the soil yield and is the highest of the hydroponic yields, which is important because only about a fifth of the plant is edible, the least of all the options. Castiel: how can alcohol be made from biomass?”

“Yeast breaks down the sugar in sugar cane to produce alcohol. Why does biomass produce less pollution than fossil fuels, Balthazar?”

“Because biomass is carbon neutral. When it’s burned, the carbon dioxide released is the same carbon dioxide that went into it when it was created. Uriel, what is meant by ‘partially permeable’? And Raphael? Get that damn stick out of your arse. He prefers the name ‘Cas’, we all know it and you’re the only one who doesn’t call him it.”

Uriel cut in. “Partially permeable means that only some substances are able to get through. And I agree with Balthazar on this one, Raphael. Who else?” Uriel looked around the group. Everyone had immediately raised their hands, looking at Raphael. The former archangel folded his arms and scowled. Uriel smiled.

“Now we know everyone’s thoughts on that, we shall continue. Anna: which statement best describes why the level rises in the sea water tank?”

“I’ve already done this whole ‘growing up’ thing. It ended in a mental asylum when Dean here was saved. It’s the first one – osmosis causes water to move from the dilute to the concentrated salt solution. What is the name of the green chemical in the celery leaves that absorbs sunlight, Naomi? Actually, now I think about it, it’s a lot like you. Sucking the happiness out of everything.”

“Hey! I had Heaven’s best interests in mind-“

“Yeah, ‘cause that always turns out so well, doesn’t it?” Dean grumbled. He hated being 16 again, especially because Sam, like everyone else, was the same age and consequently still taller than he was.

“Shut up, Dean,” Naomi rolled her eyes at him. “Not everyone has the typical Winchester luck. The chemical is chlorophyll. Stop sulking, idiot. Michael: name the two cell layers the celery leaf miner has eaten from.”

“Uh, the spongy mesophyll and…the…uh…Stop laughing, Luci, you know I always hated biology. Mrs. Bliknam hasn’t improved that opinion much either. Uh, shit. I don’t know. Shut it, Gabriel.” Michael hated admitting defeat, but he had no choice on this one. “Let’s see how well you do. Explain why the celery plant does not grow as well when these particular cells are eaten.”

Gabriel laughed. “The plant doesn’t grow as well because the cells aid respiration and energy conversion in the plant. Without the cells for those processes the plants’ growth is stunted. Sammy, what is Bacteria A which converts compost into ammonium compounds?”

“Bacteria A are saprophytes, I think. Bacteria B are nitrifying bacteria. And Michael, the other layer is the palisade mesophyll. It contains a load of chloroplasts, so losing it reduces the amount of sunlight absorbed and therefore the amount of energy that can be made, so the plant can’t grow as well. Dean, why are the nitrates produced more slowly in cold weather?”

“Cause they want to stay in their nice warm beds.” Dean deadpanned, face completely straight, but Sam could see the corners of his mouth twitching. “Nah, it’s cause the bacteria work better in warm conditions. Too warm and they die though. Luci, which two statements best explain why nitrates can only be absorbed by the roots if there is enough oxygen in the soil?”

Lucifer looked at the list for a moment before speaking. “I’m guessing the fourth and fifth statements: diffusion of minerals occurs faster in high oxygen levels and plants take up minerals from a high concentration in the soil. The second statement is a possibility, but the others don’t follow.”

Chapter Text

Lucifer turned the page. “Raphael, you start us on chemistry. Lucky you. Word equation for neutralisation.”

Raphael’s eyes widened. Gabriel sniggered, before Michael elbowed his ribs. “Uh…acid plus base equals water plus…salt? Yeah, salt. Casti- Fine. ‘Cas’, what’s the ionic equation?”

“H plus add OH minus equal H2O. Balthazar, what is Mary’s percentage yield if she expects to make 4.8g of fertiliser but only gets 4.2g?”

Balthazar screwed his face up before admitting defeat and reaching for the calculator. Maths never had been his strong point. “Ah, four point eight divided by one, zero, zero equals…0.048. So four point two divided by zero point zero, four, eight equals…87.5 percentage yield! Uriel! Word equation for copper oxide and sulphuric acid!”

“Copper oxide plus sulphuric acid equals copper sulphide plus water. Anna, complete the word equation in question E.”

“Magnesium carbonate plus sulphuric acid equals magnesium sulphate plus water plus…carbon dioxide. Nao- Michael, you may want to grab something to eat. Your stomach’s rumbling, I can hear it from here. That’s your body’s way of telling you you’re hungry. Grab a bag of chips or something. Anyway, Naomi. Calculate the mass of urea that can be made from 17 tonnes of ammonia.”

Naomi closed her eyes in concentration. “Balthazar, I need the calculator. Thanks,” she said, opening her eyes. “Okay, so the total mass is…78. Ammonia has a mass of…34 which is…43.6%of the total mass.” She was punching sums into the calculator as she spoke. “So 17 divided by 43.6…times 100 equals 39 tonnes total. Urea has a mass of 60 which is…76.92% total mass. 39 divided by one hundred…times 76.92 equals…30 tonnes of urea can be made. That’s a confusing one. So, Michael, hope your chemistry skills are better than your biology skills. Tell me one way chemicals can be-” she stifled a giggle, “-can be extracted from plants.”

“Always with the plants.” Michael sighed. “Alright. You can get morphine from poppies by crushing the poppy to break it open. You then boil the poppy and dissolve the chemicals from it in a suitable solvent. The mixture is filtered to remove insoluble substances. Once that is done, the chemicals are separated using chromatography. The solution is washed through a tube using a gas or liquid, depending on what is most appropriate. Different substances move at different speeds and are collected as they emerge to ensure that they are pure. Gabriel,” the youngest archangel looked at the oldest. “Please explain why medicines may take several years to develop.”

Everyone cringed at Gabriel’s sly look. He snapped his fingers, then laughed at their expressions: they had all winced as one. “Come on, guys! You know I don’t have any mojo, same as the rest of you!”

“Knowing you, Gabe, anything’s possible. As far as we know, this is your fault and you’ve affected yourself to avoid suspicion. Just answer the damn question already.” Sam said, getting irritable.

“Fine, fine, Mooster. They may take a while to develop because they have to undergo numerous tests to make sure they will not harm the recipient in any way and are fit for human consumption. They then have to be tested to see if they actually work like they’re supposed to. Only then can they be marketed. Now, Samoose, suggest to me-” He waggled his eyebrows at Sam, receiving an eye-roll in response-“how nitrates could get into drinking water.”

“If fertiliser and pesticide are used near the waterway, the excess runoff could get into the water. Okay, Dean…uh, actually, we haven’t covered water purification yet. You get to start us on the physics section.”

Chapter Text

“Great. ‘Cause I just love physics.” The sarcasm was clear in Dean’s voice. “Go on, Sam. Hit me with it.”

“Okay…Lorna wears a nylon coat, which becomes charged. This is because charged particles move between the coat and Lorna. What is the name of the charged particle involved?” Sam shook his head in exasperation at Dean’s immediate reaction.

“Is Lorna hot?” His goofy grin received another eye-roll. “Alright, alright, fine. Killjoy. Its called an electron. Luci, how is static electricity used to restart a heart when it has stopped? I need both the method and the safety precautions.”

“The static electric charge is passed through the body via paddles with good electrical contact with the body in the correct places. The shock causes the heart to contract and resume a normal rhythm. The safety precautions are insulated handles so the operator does not receive a shock and a spoken order to ‘stand clear’ before the shock is delivered, to protect everyone with the sense to obey. Safety’s boring, no fun at all. Raphael, calculate the resistance of the resistor with 15V and 4A in the circuit.” He slid the calculator over to his little brother without thinking about it. Everyone froze and stared at him.

“What?” Lucifer looked around at them. “What did I do?”

“You slid the calculator over to Raphael, that’s what you did. The calculator that was over by Naomi, on the other side of the table!” Dean answered, the only one capable of coherent speech at that moment. The sudden sound of the snap! of fingers and following rustle of plastic wrapping made the table of teens jump.

“We’re getting our mojo back! Finally! I can eat sweets galore again!” Gabriel was grinning like a madman, mouth full of KitKat.

“3.75 ohms. We’re still 16, we still have human memory capabilities and we still need to take the exams.” Raphael effectively killed the celebrations. “Cas, how does ultrasound produce images of the body’s internal organs, including the properties that make it suitable to use and how the image is built up?”

“The ultrasound wave is sent into the patient’s body. At each boundary between different tissues or organs some waves are reflected. The depth of the boundary is calculated by how long it takes the wave to return. The echoes are processed to produce an image. The ultrasound wave has a small amplitude and low energy, so it does not harm the patient in any way unlike X-rays. Balthazar, why do doctors prefer to use ultrasound rather than X-rays for many diagnoses?”

It was a moment before Balthazar responded. “I can’t get my alcohol! I even tried to get a KitKat like Gabriel, but nothing! Absolutely nothing! Bloody archangels. What was the question? Oh, right, yes. X-rays are a form of radiation, which can kill healthy living cells. They can also only distinguish between soft and hard tissue, making them perfect for viewing bones but not for organ diagnosis. Ultrasound can scan the soft tissue and distinguish between different kinds without causing damage. Uriel, what is meant by half-life?”

“It is the time it takes for angels to absorb half the energy of a radioactive substance. An-” He was cut off by Sam.

“The time it takes for angels to absorb half the energy? Uh, Uriel? You do need to pass the exam, which means answering according to the mark scheme, which means answering in scientific terms. Scientists – human scientists, anyway – don’t tend to think angels actually exist. The accepted answer, if not the entirely true version, is that the half-life is the time it takes for half the atoms in a radioactive substance to deteriorate.”

“Fine. I will answer to your substandard, mud-monkey level of knowledge and ignorance. Anna, sodium-24 is used in a hospital 30 hours after leaving the manufacturer with a half-life of 15 hours. It has reached a count rate of 160cpm by the time it is used. What was it’s count rate upon leaving the manufacturer?”

“160 times two times two is 320…640cpm. That was fairly easy. Um, Naomi…Scientists measure the amounts of two elements in a sample of rock. The radioactive element…”

“Plutonium slowly changes into what, Michael?”

“Uranium. The age of the rock can be calculated by…Gabriel?”

“By carbon dating the rock.”

“What in the Hell is carbon dating?” No-one was expecting the new voice. Looking over to the door, Dean groaned. Sam wasn’t far behind. The ex-angels were automatically on the defensive, all except for Cas, who remained indifferent to the room’s demonic addition.

“It is using the count rate of the carbon within a sample and cross-referencing that with the known half-life and starting count rate to estimate the age of the sample. It is a fairly modern process, which would explain your lack of knowledge on the subject, Crowley. You would have still been in Hell at the time it was developed.” The demon gaped at the passive angel, finally recognising him.

“So you lot are…what, 16? And I’ve just been dropped here in the 14 year-old version of my meat-suit with a similarly afflicted Meg, Abaddon and random blond kid. Then I walk in on the Winchesters, their pet angel and a bunch of- Bollocks! Gabriel! I’ll just skedaddle this way then!” The young demon ducked back out of the room, leaving 11 perplexed teens in his wake.

“Guess we have another two years here then.” Gabriel smiled round the group, sucking on a red lollipop.

“What are we studying at sixth form?”