10 most difficult water riddlesWater quiz
What is exactly the pH value of distilled water?
It depends on the temperature
Pure water is about 7 at 25 °C; this value decreases with increasing temperatures. At 50 °C, it is 6.55. It is also worth to note, that water that has been exposed to air is mildly acidic, because it absorbs carbon dioxide from the air.
What does synthesis gas (water gas) consist of?
oxygen (O2) and hydrogen (H2)
methane (CH4) and water (H2O)
carbon dioxide (CO2) and hydrogen (H2)
carbon monoxide (CO) and hydrogen (H2)
Water gas is a mixture of carbon monoxide and hydrogen produced from synthesis gas. Synthesis gas is a useful product, but requires careful handling due to its flammability and the risk of carbon monoxide poisoning. The water-gas shift reaction can be used to reduce the carbon monoxide while producing additional hydrogen, resulting in water gas.
Which place in the world has the highest average annual precipitation?
Central Amazon Basin
Southern foothills of the Himalayas
Mawsynram village in northeast India has the highest average annual total precipitation in the world (11,872 mm = 467.4 in). There, hot and moist air from the south of India approaches Himalayas. It rises up, cools and loses water.
Where does water boil at the temperature 37 °C (98.6 °F)?
in a microwave oven
at the Armstrong's line
at the Kármán line
on Mount Everest
The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body. Humans absolutely cannot survive above this limit in an unpressurized environment. Above Earth, this begins at 18–19 km (11–12 mi; 59,000–62,000 ft) above sea level. The term is named after United States Air Force General Harry George Armstrong, who was the first to recognize this phenomenon
What sound can be heard when approaching an iceberg?
a cracking noise
When a piece of iceberg ice melts, it makes a fizzing sound called "Bergie Seltzer". This sound is made when the water-ice interface reaches compressed air bubbles trapped in the ice. As this happens, each bubble bursts, making a 'popping' sound. The bubbles contain air trapped in snow layers very early in the history of the ice, that eventually got buried to a given depth (up to several kilometers) and pressurized as it transformed into firn then to glacial ice.
What is represented by the the colour range in this map?
sea currents speed
Launched June 10, 2011, Aquarius is NASA’s first satellite instrument specifically designed to study the salt content of ocean surface waters. The complete first year dataset of NASA's Aquarius instrument reveals seasonal changes in the Amazon River's plume. Depending on the prevailing currents, the river's freshwater outflow heads east toward Africa or bends up north to the Caribbean.
At what temperature does the water have the highest density?
Increasing the temperature generally decreases the density, but water is a notable exception: the density of water increases between its melting point at 0 °C and 4 °C. Similar behavior is observed in silicon at low temperatures.
Where is the Gulf of Bothnia?
between Finland and Russia
between Sweden and Finland
between Sweden and Denmark
between Finland and Estonia
A number of rivers from both countries flow into the gulf. As a result, a salinity gradient exists from north to south. In the south the water is the normal brackish water of the Baltic Sea, but in the north, the salinity is so low, that one can no longer taste the salt in the water and many freshwater fish thrive in it.