Chemistry quiz

More questions about Chemistry

These visible examples show the question style. LearnClash turns the full topic into ranked duels and spaced repetition.

1. 1 Easy

   What gas makes soda fizzy?

   Answer: Carbon dioxide

   Why: Carbon dioxide is pressed into soda under pressure, and part of it turns into carbonic acid, the source of that sour bite.

2. 2 Medium

   What element replaces iron in the blood of an octopus?

   Answer: Copper

   Why: The substitute carries oxygen better in cold, low-oxygen water, and it is what turns the blood blue rather than red.

3. 3 Hard

   Which substance is theoretically harder than a standard cubic diamond?

   Answer: Wurtzite boron nitride

   Why: A 2009 simulation ranked wurtzite boron nitride 18 percent above diamond, yet samples measured in 2019 came out softer than cubic boron nitride.

4. 4 Easy

   What chart arranges all the chemical elements?

   Answer: Periodic table

   Why: Mendeleev's 1869 table listed the 63 elements then known and left gaps; gallium, scandium and germanium later filled them. Today it holds 118.

5. 5 Medium

   At what temperature Celsius does water reach its maximum density?

   Answer: 4°C

   Why: Water is densest near 3.98 °C, and the platinum kilogram of 1799 was made to match one cubic decimetre of water at that maximum density.

6. 6 Hard

   What gives gold its distinctive yellow colour?

   Answer: Relativistic effects

   Why: Its electrons move fast enough for Einstein’s corrections to matter, which shifts the light it absorbs out of the ultraviolet and into the blue.