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23. Why Do Onions Make You Cry?

vapor

випар

aside from

крім, за винятком

to release

випускати

to eat

в’їдатися (про кислоту)

sulfuric acid

сірчана кислота

volatile

летючий

an irritant

подразник

to waft

доноситися (про запах)

to smell

відчувати запах

to wipe

витирати

to remove

усунути (щось)

to reduce

зменшувати

odor (smell)

запах

to burn

обпалювати

Unless you’ve avoided cooking, you’ve probably cut up an onion and experienced the burning and tearing you get from the vapors. When you cut an onion, you break cells, releasing their contents. Amino acid sulfoxides form sulfenic acids. Enzymes that were kept separate now are free to mix with the sulfenic acids to produce propanethiol S-oxide, a volatile sulfur compound that wafts upward toward your eyes. This gas reacts with the water in your tears to form sulfuric acid. The sulfuric acid burns, stimulating your eyes to release more tears to wash the irritant away.

Cooking the onion inactivates the enzyme, so while the smell of cooked onions may be strong, it doesn’t burn your eyes. Aside from wearing safety goggles or running a fan, you can keep from crying by refrigerating your onion before cutting it (which slows reactions and changes the chemistry inside the onion) or by cutting the onion under water.

The sulfur-containing compounds also leave a characteristic odor on your fingers. You may be able to remove or reduce some of the smell by wiping your fingers on a stainless steel odor eater. You just rub your fingers across the blade of a stainless steel knife to remove odors from onions, garlic, and fish.

Speech patterns

Unless

Якщо не …

Unless you’ve avoided cooking, you’ve probably cut up an onion.

Якщо ви не цуралися приготування їжі, ви вочевидь різали цибулю.

1. Use special questions to write a plan to the following text.

2. Translate the abstract given below.

В тексті розглядається вплив сірчаної кислоти на виникнення печії та сліз при приготуванні цибулі. Аналізуються хімічні процеси, що відбуваються під час різання цибулі. Показано, що сірчана суміш легко випаровується та взаємодіє з водою сліз людини, спричинюючи обпалення та збільшуючи кількість сліз. Представлені методи запобігання впливу ензимів на сльозову оболонку очей та усунення запаху на пальцях.

Grammar Practice

1. Write down the names of the acids metioned in the text into several lists according to their suffixes.

2. Find all -ing verb forms in the text and explain their functions.

3. Find all the sentences with subordinate clauses in the text. Define their functions.

24. Key Step Made Towards Turning Methane Gas Into Liquid Fuel

to be valued

цінитись за шось

readily

легко, просто

a bond

з’єднання

currently

в даний час

to bind

зв’язувати

a catalyst

каталізатор

to burn

горіти, спалювати

inefficient

неефективний

to break

розривати

selectively

вибірково

carbon

вуглець

advance

досягнення

hydrogen

водень

to transform

перетворювати

to convert

перетворювати

required

необхідний

Researchers at the University of Washington and the University of North Carolina at Chapel Hill have taken an important step in converting methane gas to a liquid, potentially making it more useful as a fuel and as a source for making other chemicals. Methane is valued for its high-energy carbon-hydrogen bonds, which consist of a carbon atom bound to four hydrogen atoms. The gas does not react easily with other materials and so it is most often simply burned as fuel. Burning breaks all four hydrogen-carbon bonds and produces carbon dioxide and water. Converting methane into useful chemicals, including readily transported liquids, currently requires high temperatures and a lot of energy. Catalysts that turn methane into other chemicals at lower temperatures have been discovered, but they have proven to be too slow, too inefficient or too expensive for industrial applications. Binding methane to a metal catalyst is the first step required to selectively break just one of the carbon-hydrogen bonds in the process of converting the gas to methanol or another liquid. The work should stimulate further advances in developing catalysts to transform methane into methanol or other liquids.

Speech patterns

They

prove

to be

good specialists.

Виявляється, що вони хороші спеціалісти.

appear

turn

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