Science and Experiment

The unit opens with two pictures. In the first, a schoolgirl in a laboratory looks through a microscope, with another microscope beside her and a model of the human body and a picture of leaves on the wall behind. The second shows four pieces of glassware holding colored liquids: a round-bottomed flask, a conical flask, a beaker with a lip for pouring, and a tall, thin measuring cylinder.

Before you read

The picture shows a glass pot of water boiling on a gas stove, its bubbles rising to the top.

What kind of text it is

The text is a popular science article by Rhett Allain, a physics professor in the United States, from his column in the magazine Wired. Popular science explains science to ordinary readers, so it is written in a chatty, friendly voice: Allain talks to you (Picture a glass of water), jokes (No one cooks rice at the top of Everest), uses comparisons from daily life, and keeps saying But wait! before a new idea. Its American measures are in °F and feet; the explanations below give them in °C and meters too.

The article, part by part

1. Why rice packets have high-altitude instructions

Some packets of rice in the United States give a second set of cooking instructions for high altitude: in a city like Denver, which is about 1,600 meters above sea level, the rice must cook a bit longer. Why should it matter where you cook? The answer, says Allain, has to do with boiling water.

2. Water doesn’t always boil at 100 °C

Ask people when water boils and they will say 212 °F, or 100 °C. That is true only at sea level. As you go higher, the boiling point falls, by about 1 °F for every 500 feet (roughly 1 °C for every 300 meters). In Denver, water boils at about 203 °F, about 95 °C, and food in water at 95 °C cooks more slowly.

3. Water vapor without boiling

Water is special: on the Earth’s surface it is found in all three phases, as solid (ice), liquid and gas. The gas is water vapor. You don’t have to boil water to make vapor: a glass of water on a table is enough.

Imagine zooming in on the water until you see its molecules (each is two hydrogen atoms and one oxygen atom, but think of them as tiny balls). The balls are always jiggling about and bumping their neighbors. This is thermal motion: the hotter the water, the faster they move. Not all of them move at the same speed. There is an average speed, but some are faster and some slower, just as a group of adults has an average height, with a few who are very tall.

The fastest balls near the surface have enough energy to break free of the liquid: they become vapor. And it works the other way too: some vapor balls hit the water and join the liquid again.

4. Vapor pressure

In a closed container, the water soon reaches equilibrium, a balance: as many balls leave the liquid each second as come back into it. The pressure of the vapor above the water at that balance is the vapor pressure. You can see the vapor in a closed bottle: it condenses into drops on the inside of the walls. The hotter the water, the higher its vapor pressure.

5. What the bubbles are made of

When water boils, what is inside the bubbles? Not air (where would it come from?), and not hydrogen and oxygen (the water isn’t being split up). The bubbles are pockets of water vapor.

To make a bubble, molecules must have enough energy to push the surrounding water aside. But a bubble also needs pressure inside it to stay open: the vapor pressure inside must be at least equal to the pressure of the water outside, or the bubble is crushed. So:

Water boils when its vapor pressure rises to equal the pressure outside, on its surface.

6. The pressure outside

The pressure on the water comes from two things:

• the water itself: deeper water is pressed by the water above it, so the pressure depends on the depth, the density of water and gravity. In a glass this is tiny: 2 cm below the surface the pressure is only about 0.2 percent more than at the top;
• the atmosphere: the air presses down on the surface of the water, and this is by far the bigger part.

7. Lower the pressure, and water boils without heat

So what if you lower the air pressure on the water? Bring it down to the water’s vapor pressure, and the water boils, without getting any hotter. With a vacuum pump and a strong flask, you can make water boil at room temperature, and hold the boiling flask in your hand, because it isn’t hot.

You can try it with a large plastic syringe: draw in some water with as little air as possible, seal the tip, and warm the water a little. Allain sealed his with hot glue, a rubber stopper and a Lego piece, and warmed the water to about 42 °C. Then he pulled the plunger back hard. That lowers the pressure inside and induces (causes) boiling. It is hard work, and you can’t pull a perfect vacuum, which is why the water was warmed a little first: at 42 °C the vapor pressure is higher, so less pulling is needed.

8. Back to the rice

This is what happens to rice at high altitude, Allain ends, except that there is no giant plunger: gravity holds the atmosphere down on the Earth, and higher up there is less air above you pressing down, so water boils at a lower temperature.

Words from the article

Word	Meaning here
altitude	height above sea level
molecule	the smallest particle of a substance, a group of atoms joined together (H₂O)
factoid	a small, interesting fact (in American use, as here); it can also mean something untrue that people repeat until it is believed
phase	a state of matter: solid, liquid or gas
thermal motion	the constant random movement of particles, faster when hotter
equilibrium	a state of balance between two opposite changes
vapor pressure	the pressure of a liquid’s vapor in balance with the liquid (British vapour)
condense	to change from gas to liquid
vacuum	a space with all, or almost all, the air taken out
plunger	the part of a syringe (or a pump) that slides in and out of the tube
induce	to cause something to happen
jiggle	to move quickly up and down or from side to side

A. Find the words

B. Complete the sentences

C. Answer the questions

Many English words sound the same but are spelled differently and mean different things (homophones: sale and sail). Others are spelled almost alike but sound different (sale and sell). Listening for the vowel sound is the key.

A. Conversations of cause and result

In the first conversation, three friends talk about a race: Deshika asks who will win, Saloni thinks Punam will, and Shristi agrees: if Punam runs faster, she will beat them all. In the second, Sirjana asks why she has to study hard; Kritika says that if she studies hard she will get better results, and Manoj adds that with good results she can get a scholarship.

Each reply builds on the last with an if-sentence about a real possibility in the future: If you study hard, you will get better results. If you get good results, you can get a scholarship. This is a chain of the first conditional, which Grammar I explains.

B. Make a chain

C. If you were…

The second set imagines things that are not true: If you were a food item, what would you be? If I were a food item, I would be an apple, because if people ate an apple a day, they would stay healthy. This is the second conditional: if + past, would + verb.

A conditional sentence has two parts: an if-clause (the condition) and a main clause (the result). Either can come first; when the if-clause comes first, put a comma after it. Which tenses you use depends on when it is about and how likely it is.

Type	Used for	if-clause	main clause	Example
Zero	facts, things that always happen	present	present	If you heat ice, it melts.
First	a real possibility in the future	present	will / can / may + base verb	If it rains, we will stay at home.
Second	something imagined, unlikely or untrue now	past (were for be)	would / could / might + base verb	If I were a bird, I would fly over the hills.
Third	something imagined in the past, which didn’t happen	had + past participle	would have + past participle	If I had known, I would have called you.

The third type is the subject of Grammar II, with sentences that leave out if.

Other words that work like if:

• unless = if … not: The horse won’t kick you unless you go behind it (= if you don’t go behind it). Its verb is positive: ✗ unless you don’t go.
• provided (that) and as long as = only if, on condition that: You can borrow my bike as long as you bring it back by six.
• in case = because it might happen: Take an umbrella in case it rains.

A. Match the halves

B. Put the verbs in the right form

The task shows a cartoon jellyfish drawn in six steps, and asks you to write the steps as instructions, using the words circle, lines, semi-straight, creaky (here: wavy, bent), on top of, above, below.

How to write instructions

Instructions tell someone how to do something, step by step: a recipe, a game’s rules, how to use a machine, how to draw.

• Give a title that says what the instructions are for, and list what is needed.
• Number the steps, in the order they are done, one action in each.
• Begin each step with an imperative verb: Draw…, Add…, Fold…, Pour…
• Use sequence words: first, next, then, after that, now, finally.
• Use position words to say exactly where: above, below, on top of, beside, in the middle of, at the end of.
• Keep sentences short; add a tip or a warning where it helps (Press lightly, so you can rub it out).

Before you read

The picture before the poem shows a man standing outside in the rain, face turned up and eyes closed, enjoying it.

The poet and the poem

Walt Whitman (1819–1892) was an American poet, famous for Leaves of Grass, a book he kept adding to all his life. He wrote in free verse, long lines without rhyme or a regular beat, which was new in his time. The Voice of the Rain is a short poem from his old age, first printed in 1885.

The poem, part by part

The poem is a conversation between the poet and the rain. Its old-fashioned words: art thou (are you), whence (from where), form’d (formed), lave (wash), reck’d or unreck’d (noticed or unnoticed, cared about or not).

Lines 1–2: The question

The poet asks the gently falling shower who it is. To his surprise, it answers, and he gives its answer in English, “as here translated”.

Lines 3–5: The rain rises

The rain says that it is the Poem of the Earth. It rises forever, impalpable (too fine to be touched or felt: invisible vapor), out of the land and the bottomless sea, up into the sky, where it takes shape vaguely as clouds, completely changed, and yet the same water.

Lines 6–8: The rain comes down

It comes down to wash the dry places, the tiny specks (atomies) and layers of dust on the globe. Without it, all the seeds in the soil would stay only seeds, latent (hidden, waiting) and unborn. By day and night it gives life back to the Earth it came from, and makes it pure and beautiful.

Lines 9–10: Rain is like a song

The last two lines, in brackets, compare the rain to a song: a song comes from the poet’s heart (its birthplace), goes out into the world, wanders, and does its work, whether anyone notices it or not; then it comes back with love, in the response of the listeners. The rain does the same: from the Earth to the sky and back to the Earth.

The poet’s devices:

• Personification: the rain speaks and calls itself a poem.
• Metaphor: I am the Poem of Earth. A poem gives beauty and meaning; so does the rain.
• A cycle: rise → change → descend → return, the water cycle, told as a story.
• Contrast (opposites): rise / descend, day / night, changed / the same, heaven / earth, reck’d / unreck’d.
• Comparison in the last two lines: the rain’s journey is set beside a song’s, which also goes out and returns.

Words from the poem

Word	Meaning here
eternal	lasting forever, without end
impalpable	that cannot be touched or felt
vaguely	not clearly
descend	to come down
lave	(old) to wash
atomies	(old) tiny particles, specks
reck	(old) to care about, take notice of
latent	present but hidden, not yet grown or shown
globe	the Earth
drought	a long time without rain
beautify	to make beautiful
origin	the place something comes from

A. Match the words with their meanings

B. Fill in the blanks

C. Complete the summary

D. Answer the questions

The textbook’s listening task describes a simple experiment with liquids in a glass. CDC’s own recording is below: read the questions in B and C first, then listen, as many times as you need. After the answers, practice with a talk of our own that your browser reads aloud.

A. Before you listen

The picture shows a glass with three layers of colored liquid, one on top of another, and small objects resting at different levels.

B and C. The textbook’s audio: answers

The third conditional

The third conditional imagines a different past: something that did not happen, and what its result would have been.

If + had + past participle, would / could / might + have + past participle
If we had harvested rainwater, the crisis would have been less serious. (We didn’t, and it was serious.)
If he hadn’t come to Nepal, he wouldn’t have seen Everest. (He came, and saw it.)

A mixed conditional joins a past condition to a present result: If I had studied harder, I would be at the university now.

Without if: inversion

In formal English, if can be left out and the verb put before the subject. The meaning stays the same:

With if	Without if	Type
If you should need help, call me.	Should you need help, call me.	first (a little more polite and less likely)
If Rijisa were in the USA, she would be working there.	Were Rijisa in the USA, she would be working there.	second
If he were to see me, he would know me.	Were he to see me, he would know me.	second (an unlikely future)
If I had known, I would have called you.	Had I known, I would have called you.	third

Only these three verbs, should, were and had, can be turned round like this. A negative keeps not after the subject: Had I not seen the sign… (not ✗ Hadn’t I seen…).

If … were to + verb puts an imagined, unlikely event in the future: If the Bagmati were to flood tomorrow, the low houses would be underwater.

A. Put the verbs in the right form

B. Complete the sentences

A. Rujuna’s letter about water

The textbook’s model is a letter to the editor of The Rising Nepal, a national daily, written on 19 May 2022 by Rujuna Manandhar of Koteshwor, Kathmandu, about the shortage of water in her area. Its parts:

Part	What Rujuna does
Opening	She draws the authorities’ attention to the problem: water has been scarce for a long time, and if nothing is done, neighbors may end up fighting over a few drops.
The causes	The local water tank is too small for everyone’s needs, and yet residents waste water while bathing, washing clothes and dishes, and gardening.
Suggestions	A meeting of all residents; messages on local cable TV and community radio; a door-to-door campaign; experts to show ways to save water; reusing water. Had they started harvesting rainwater, she adds, the crisis would already be smaller.
Closing	She hopes quick action will be taken, thanks the editor and signs off Yours truly.

It uses conditionals to argue: If this goes on unchecked, people are likely to fight…; If we organize a door-to-door campaign, it is sure to…; Had we gone for rainwater harvesting…, it would certainly have lessened the crisis.

How to write a letter to the editor or a letter of complaint

A letter to the editor is written to a newspaper, to be printed for the public: it raises a problem everyone should know about. A letter of complaint goes straight to the person or office that can fix the problem (a ward office, a municipality, a company). Both are formal letters.

1. Your address and the date.
2. The recipient: The Editor, The Rising Nepal, Dharmapath, Kathmandu, or The Mayor / The Ward Chairperson, …
3. Subject (in a complaint): Complaint about unmanaged garbage in Ward No. 7.
4. Salutation: Dear Sir/Madam, (or Dear Editor,)
5. Paragraph 1: the problem, and where; why you are writing.
6. Paragraph 2: details and effects, with an example; who is affected.
7. Paragraph 3: your suggestions, specific and possible.
8. Closing: a hope for action, thanks; Yours faithfully (or Yours truly), your name.

Keep it polite even when you are angry: facts persuade, insults don’t.

B. A letter of complaint about garbage

These pairs (and one group of three) look or sound alike, so they are easily mixed up in writing.

Word	Part of speech and meaning	Example
accept	verb: to receive, or to agree to	I accepted all my birthday gifts with thanks.
except	preposition: apart from, not including	Everyone came except Hari.
expect	verb: to think something will happen; to wait for	I expect that they will win the match.
affect	verb: to have an effect on, to change; to move someone’s feelings	The dog’s death affected its owners deeply.
effect	noun: a result, a change caused by something	The new principal’s rules had a good effect on the students. (effect as a verb, formal, means to bring about: to effect a change)
borrow	verb: to take something for a time, to give it back later	May I borrow a pencil, please?
lend	verb: to give something for a time, to get it back later	Would you please lend me a pencil?
breath /breθ/	noun: the air you take in and let out	Take a deep breath.
breathe /briːð/	verb: to take air in and let it out	Just calm down and breathe.
complement	noun: something that completes or goes well with something; verb: to complete, go well with	Achar is a nice complement to dal bhat.
compliment	noun: words of praise; verb: to praise	She paid me a compliment on my speech.
lose /luːz/	verb: to be unable to find; to fail to win	Did you lose your glasses again?
loose /luːs/	adjective: not tight; not fixed	These trousers are loose since I lost weight.
principal	noun: the head of a school; adjective: main, most important	The principal reason for the meeting is the budget.
principle	noun: a basic rule or belief; a scientific law	Her parents taught her strong moral principles.
stationary	adjective: not moving	The truck was stationary at the red light.
stationery	noun: paper, envelopes, pens	The school buys stationery every April.

SEE-style practice on this unit. Try each one as in the exam, then open the answer.