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Going Further, Grades 9–12

Topics past the school course for students in Grades 9 to 12: each starts from what you learned in class and goes further, with things to play with and questions to try. Not in any exam.

Start reading: Topic 1 · Why Does Salt Melt at 801 °C but Ice at 0 °C? →

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Physical science

Matter and chemistry NGSS HS-PS1

Already in your grade books
  1. Topic 1Forces between particles Why Does Salt Melt at 801 °C but Ice at 0 °C? Water and methane molecules are almost the same size, yet water boils at 100 °C and methane at −162 °C. Why?  
  2. Topic 2Bond energy Why Do Some Reactions Get Hot? The gas in the cylinder is cold, and so is the air. Mix them, add a spark, and out roars heat. Where was it hiding?  
  3. Topic 3Collision theory What Makes a Reaction Go Faster? A fridge takes barely a tenth of the milk’s energy away, yet milk that would sour by evening keeps for days. Why?  
  4. Topic 4Chemical equilibrium Why Do Some Reactions Stop Halfway? Nitrogen and hydrogen over hot iron stop changing when only a quarter is ammonia, however long you wait. Why stop halfway?  
  5. Topic 5The mole and conservation of mass How Do You Count Atoms by Weighing Them? Nobody counts the rice at the shop: they weigh it. Chemists count atoms the same way, though nobody can see one.  
  6. Topic 6Radioactive decay, fission and fusion What Happens Inside a Nucleus When It Decays? Every second, thousands of atoms in your body become a different element, the alchemists’ dream. What happens inside them?  
  7. Topic 48Atomic structure and the quantum atom Where Is the Electron? Grade 9 draws electrons on neat circles. Nobody has ever seen one go round: so where is it, really?  

Forces and motion NGSS HS-PS2

Already in your grade books
  1. Topic 7Momentum and collisions Why Do Airbags Save Lives? An egg dropped on stone breaks; on a blanket it may not, though it falls just as fast. Why does how it stops matter?  
  2. Topic 8Coulomb’s law and gravitation Why Is Gravity So Weak? The whole Earth pulls a scrap of paper down; a comb rubbed in your hair lifts it up, and wins. Why is gravity so weak?  
  3. Topic 9Molecular structure and materials Why Is Spider Silk So Strong? A thread thinner than a hair stops a flying fly, and weight for weight beats steel. Its secret isn’t what it’s made of.  

Energy NGSS HS-PS3

  1. Topic 10Conservation of energy Where Does the Energy Go When a Ball Bounces? Energy is never destroyed, yet a dropped ball bounces lower each time and then lies still. Where did its energy go?  
  2. Topic 11The second law of thermodynamics Why Does Heat Never Flow from Cold to Hot? Hot chiya cools on the table; cold chiya never heats itself up, though no law of energy forbids it. So what does?  
  3. Topic 12Fields and stored energy How Do Magnets Push Without Touching? Two magnets jump together with a click, though nothing was burnt or wound up. Where did the energy of the jump come from?  
  4. Topic 13Energy conversion devices How Much Electricity Can a Small Stream Make? A hill stream has turned the ghatta’s millstone for centuries; now it can light a village. How much power can it make?  

Waves and light NGSS HS-PS4

Already in your grade books
  1. Topic 14Spectra and photons What Are Stars Made Of? Nobody has been to a star, yet we know what they’re made of. Learn to read the barcode hidden in starlight.  
  2. Topic 15The wave and particle models of light Is Light a Wave or a Stream of Particles? Light spreads and interferes like a wave, yet knocks electrons out of metal like a hail of particles.  
  3. Topic 16Electromagnetic radiation and health Is Phone Radiation Dangerous? A WhatsApp message says the new phone tower will give children cancer. Is it right, and how can you judge for yourself?  

Life science

Cells and the body NGSS HS-LS1

Already in your grade books
  1. Topic 17Protein synthesis How Does a Gene Make a Protein? Chew plain rice and it turns sweet, thanks to a tool built from instructions in four letters. How does a cell read them?  
  2. Topic 18Homeostasis and feedback How Does Your Body Stay at 37 °C? Winter in Jumla or summer in the Terai, your inside stays almost the same. Feedback loops that keep it steady.  
  3. Topic 19Cell division and differentiation How Does One Cell Become a Whole Person? You began as one cell. How it became trillions, and how cells with the same DNA became skin, bone and brain.  
  4. Topic 20Cellular respiration and biosynthesis How Does Food Become Energy, and Become You? Some of your dal bhat becomes your muscle, and much of it you breathe out. How does rice become energy, and become you?  

Ecosystems NGSS HS-LS2

  1. Topic 21Anaerobic respiration Can Life Run Without Oxygen? Yeast making jaand, your muscles in a sprint, microbes in a flooded paddy: life that gets its energy without oxygen.  
  2. Topic 22Carrying capacity How Many Tigers Can Chitwan Hold? Nepal’s wild tigers rose from 121 in 2009 to 429 in 2026. Can they keep growing? Carrying capacity in numbers.  
  3. Topic 23Energy pyramids and the carbon cycle Where Does a Fallen Leaf Go? A sal forest drops tonnes of leaves every year, yet its floor is never buried. Where do they all go?  
  4. Topic 24Succession and ecosystem change Can a Forest Come Back? Hills left bare in the 1970s are green again under Nepal’s community forests. How ecosystems recover, and how to help.  
  5. Topic 25Group behavior Why Do Animals Live in Groups? Every pigeon in a flock competes with the others for grain, yet they stay together. Does the group really help each one?  

Heredity NGSS HS-LS3

Already in your grade books
  1. Topic 26Genetic variation Why Aren’t You Exactly Like Your Brother or Sister? Same mother, same father, yet one is tall and curly-haired and the other isn’t. How different can brothers and sisters be?  

Evolution NGSS HS-LS4

Already in your grade books
  1. Topic 28Natural selection in action Why Do Antibiotics Stop Working? The tablets that cured typhoid in Nepal for years stopped working. Nobody made a new disease, so what changed?  
  2. Topic 29Speciation and extinction How Do New Species Begin, and End? The spiny babbler lives in Nepal and nowhere else; the blackbuck here fell to nine animals. How do species begin, and end?  

Earth and space science

Earth in space NGSS HS-ESS1

  1. Topic 30The life of the Sun How Long Will the Sun Shine? A fire runs out of wood and a lamp runs out of oil. The Sun has shone for billions of years. How much longer can it go on?  
  2. Topic 31Evidence for the Big Bang How Do We Know the Universe Is Expanding? Nobody has ever seen a galaxy move, yet we know almost all of them are flying away from us. How can anyone know?  
  3. Topic 32How elements are made in stars Where Did the Atoms in Your Body Come From? Not one atom of a bride’s gold, or of the iron in your blood, was made on the Earth. So where were they made?  
  4. Topic 33Orbits Why Don’t Satellites Fall Down? They do: they fall all the time and keep missing. Using Newton’s law to work out how fast and how long each orbit takes.  
  5. Topic 34Sea-floor spreading Why Is the Sea Floor So Young? Almost no sea floor is over 200 million years old, yet some continental rock is 4 billion. Plate tectonics explains it.  
  6. Topic 35Radiometric dating and Earth’s early history How Old Is the Earth? Nobody saw the Earth form, yet tiny crystals in Trishuli sand carry clocks that have ticked ever since. How old is it?  

Earth’s systems NGSS HS-ESS2

  1. Topic 36Plate tectonics and the Earth’s interior Why Is Everest Still Rising? Something is pushing a whole country north and lifting Everest every year. Nobody has ever been down to see what.  
  2. Topic 37Water and weathering What Does Water Do to Rock? Rock seems the hardest thing there is, and water the softest. Yet water carved Pokhara’s caves and gorges. How?  
  3. Topic 38Natural climate change Why Has the Climate Changed Before? Nobody burned coal in an ice age, and nobody stopped burning it to end one. So what changed the climate before us?  
  4. Topic 39Feedback in Earth’s systems Can One Change Set Off Many More? Bare rock melts the snow around it, which bares more rock. When does one change set off more, and when does it die down?  
  5. Topic 40The carbon cycle Where Does the Carbon Go? A cylinder of cooking gas sends 43 kg of CO₂ into the air, but only about half of it stays there. Where does the rest go?  
  6. Topic 41How life and Earth changed together How Did Life Change the Air? The young Earth’s air had almost no oxygen. Bacteria made it, and changed rocks, seas and what could live.  

People and the planet NGSS HS-ESS3

  1. Topic 42Resources, hazards and settlement Why Do People Live Where They Do? Kathmandu stands on the bed of an old lake, and its rich soil is why people came. What decides where people live?  
  2. Topic 43Energy and resource choices Which Energy Should Nepal Use? In 2015 Nepal ran short of power and petrol at once. What should it build next, and which costs are worth paying?  
  3. Topic 44Reducing human impact Does the Fix Actually Work? Many valley brick kilns were rebuilt after 2015 to a zigzag design that burns less coal. Testing a fix with data.  
  4. Topic 45Sustainability How Many People Can the Earth Support? Over eight billion people, all fed from land and sea we share with millions of species. How many can the Earth hold?  
  5. Topic 46Climate data and models What Will the Climate Be Like When You Are Grown Up? How warm will the world be, and how much Himalayan ice will be left, when you are grown up? And how can anyone know?  

Engineering

Engineering NGSS HS-ETS1

  1. Topic 47Engineering design Can You Design an Earthquake-Safe House? Nepal’s 2015 earthquake destroyed about half a million homes. Can we build homes that the next one won’t knock down?  

How to use this book

These topics go past the school course, for anyone who wants to know more. Each one starts from things you learned in class, linked under its title, so you can look back. Each is a question, with the subject it belongs to beside its number. They are not in any exam. Inside you’ll find:

  • Worked examples: try them first; the answer stays hidden until you open it.
  • Try it questions and each topic’s questions at the end, with hints and answers to open when you’re ready.
  • Diagrams to play with: drag, slide and change things to see what happens.
  • Did you know? boxes with the stories and surprises behind the science.

Every fact here has been checked against reliable sources, but these topics have not yet been reviewed by subject experts. If you find a mistake, please tell us.