Ammonia production by the Haber process
How can nitrogen from the air be converted into ammonia quickly, efficiently and economically?
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↗Physics
Forces, motion and electromagnetism
Chemistry
Reactions and the molecular world
Biology
A closer look at life
Geography
Read the Earth's changing patterns
START WITH A QUESTION
What would you like to understand today?
Formation of river landforms
Why does the shoreline of the Yangtze River at Zhenjiang keep shifting northwards?
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Factors affecting reaction rate
Why do some reactions finish in seconds while others take a long time? What determines how fast a reaction proceeds?
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Apparent motion of the Sun, seasons and climate zones
Why do the Sun's altitude and direction at noon change systematically throughout the year?
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Molecular models of organic compounds
Molecular formulae are drawn on flat paper, but what are the actual three-dimensional shapes? What can a ball-and-stick model reveal?
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Titration of a strong acid with a strong base
More than 20 mL has been added with almost no visible change. Why does the final half-drop cause a clear colour change?
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Preparation and properties of chlorine
What does each part of the apparatus for preparing dry, pure chlorine do, and what happens if one part is missing?
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Pig iron production in a blast furnace
How does ore charged at the top become molten pig iron within hours, while fuel consumption is kept low?
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Metal extraction: molten-salt electrolysis and aluminothermic reduction
Why is electricity used to extract aluminium industrially, while aluminium itself can reduce iron oxide to iron?
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Ocean currents: distribution and effects
Why did tens of thousands of toy ducks lost at sea drift to coastlines around the world?
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Ocean–atmosphere interaction: El Niño and La Niña
Why can unusually warm water in the eastern Pacific cause heavy rainfall along the Peruvian coast?
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Integrated coal utilization and gasification
Is coal only a fuel to burn? How can it become a gas used to manufacture fertilizers and methanol?
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Sulfuric acid production by the contact process
How can sulfur in ore be converted into sulfuric acid rapidly, with high yield, low cost and limited pollution?
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Salt hydrolysis and its applications
Ions released by a salt may seem neither acidic nor basic. Why can they make a solution acidic or basic?
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How the atmosphere gains heat
Sunlight reaches the ground all day. Why does the ground warm first during the day and cool quickly at night? How much heat does the atmosphere retain for it?
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Formation and identification of karst landforms
Xu Xiake described sharp, isolated peaks rising in rows. How did these develop from a layer of rock?
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Cement manufacturing
Why do limestone and clay become cement for dam construction after grinding, firing and grinding again?
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Climate change and its effects
Why did the Maldives hold a cabinet meeting 6 m below sea level?
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Formation of tectonic landforms
Why are broadleaf fossils found on the Tibetan Plateau? What forces raised and then fractured its surface?
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Photoelectric effect
Why can the same light beam eject electrons from one metal but none from another? Which properties of the light determine the photoelectrons' energy?
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Charging and discharging a capacitor
What does a capacitor actually store? Can a single quantity describe its ability to store charge?
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Geographical effects of the Earth's motions
Why can it be noon in Beijing and midnight in New York at the same moment, and why are summer days longer than winter days?
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The relationship between acceleration, force and mass
Without measuring force or acceleration directly, can a paper tape and a few masses reveal the relationship between a, F and m?
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Iron and its compounds: changes in oxidation state
The element is still iron, so why does it sometimes have oxidation state +2 and sometimes +3 in a test tube? How can you tell?
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Water uptake and loss in plant cells
Vegetable leaves become firmer and crisper in clean water, but release water when salted. How do plant cells gain and lose water?
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Electrolysis of CuCl₂ solution and brine
With the same direct-current supply, why does CuCl₂ solution yield copper and chlorine, while saturated brine yields hydrogen, chlorine and NaOH?
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Preparation and properties of ammonia
Why can a flask of ammonia draw water into itself from a beaker?
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Factors that shift chemical equilibrium
When a condition changes, how can you determine the direction in which equilibrium will shift?
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Flame tests and atomic spectra
Why does each metal produce a characteristic flame colour, and how can that colour reveal a sample's composition?
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Galvanic cells: from one solution to two
If one beaker of dilute acid already produces a current, why use two compartments and a salt bridge?
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Electrolytic dissociation, conductivity and ionic reactions
Why is the same hand more susceptible to electric shock when wet?
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Verifying conservation of mechanical energy
As a mass falls, is all the decrease in gravitational potential energy converted into an increase in kinetic energy? Can paper tape help measure and test this?
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Soil-forming factors and soil profiles
Why are soils in northeastern China dark and fertile, while soils in the south are relatively nutrient-poor?
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Investigating horizontal projectile motion
Using only an inclined track and a screen, can you resolve horizontal projectile motion into two components and measure its initial velocity?
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Transport across cell membranes
Across the same cell membrane, why can oxygen pass unaided, glucose needs a transport protein, and K⁺ can still move against its concentration gradient?
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Nitric acid and interconversion of nitrogen oxides
With copper and nitric acid in both cases, why does one flask release a reddish-brown gas and the other a colourless gas?
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Centripetal force, radius, angular speed and mass
A hand-turned apparatus only gives division counts on two scales. Can these reveal the quantitative relationships between F and m, r, ω?
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Self-induction and eddy currents
Why do two lamps behave differently after a few copper turns are added to the coil? Why can a lamp flash once more after the switch opens?
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Measuring electromotive force and internal resistance
How can a voltmeter, ammeter and sliding rheostat measure an old dry cell's electromotive force and internal resistance? Does changing the circuit give the same result?
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Generation and conduction of nerve impulses
Starting within 0.1 s of the gun is classified as a false start (original textbook, p.27). How is an excitation signal transmitted through the body?
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Extraction of bromine from seawater
Seawater contains only 65 mg/L of bromine. How can it yield a bottle of liquid bromine?
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Thermally driven atmospheric circulation
Why can wind direction on the two sides of the Taiwan Strait reverse within a day?
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Observing mitosis in root-tip meristematic tissue
Which cells in an onion root tip are dividing? Can counting cells estimate the duration of each phase?
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Properties of sodium and dealing with sodium fires
Why is sodium stored under kerosene, and why must water not be used on a sodium fire?
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Sulfur, SO₂ and sulfuric acid
The element is still sulfur. Why is it sometimes a yellow solid, sometimes associated with decolourizing fuchsin solution, and sometimes combined with iron powder?
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Horizontal air movement: wind
Why does wind not blow straight from high to low pressure?
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Metal corrosion and self-heating hand warmers
Iron rusts slowly, so how can it make a hand warmer hotter than 45 ℃? How can the same principles protect iron from rusting?
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Factors affecting enzyme activity
Why does boiling water destroy an enzyme's activity, while its activity can return after it is removed from ice water?
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The chlor-alkali industry
How can caustic soda output be increased while reducing electricity use and preventing faults?
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Soda ash production by the Hou process
How can common salt and ammonia produce soda ash while also yielding nitrogen fertilizer?
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The magnetic field of a current
If a magnetic field cannot be seen or touched, how can it be represented and its direction determined?
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Brownian motion and diffusion
If molecules cannot be seen, what evidence shows that they move randomly?
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The water cycle and its geographical significance
Rivers keep carrying water into the sea, so why does the amount of seawater not increase indefinitely?
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Pressure belts, wind belts and atmospheric circulation
Why did Magellan's fleet sometimes sail against the wind and sometimes with it, yet struggle to advance near 30°S?
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FROM SCREEN TO CLASSROOMLess memorising.
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More “now I see” moments.
Project a large view for everyone to observe, or let each learner investigate independently. Guided steps take you from a question to an experiment and a conclusion.
See how to use it →Simulations support scientific exploration; combine them with real experiments and teaching materials.