grade 8 casual revision

All of these are causes of mass extinction except.................................

• Poisonous gases from volcanic eruptions

• Violent Earth movement

• Overhunting

• Meteorites impacts in Earth

The layer that is inserted in the outer apace is called...............................and its importance is...........................

• exosphere, protect the earth from celestial rocky masses

• ionosphere, in wireless communication

• exosphere, satellites fly in it for weather broadcasting

• thermosphere, satellites fly in it

The atomic number of element exists in period 4 group 1A is......................................

• 19
• 8
• 25
• 12

The type of fossil in this picture is............................

• petrified fossil

• cast

• mold

• fossil of complete body

Erosion of ozone layer occurs due to all of the following expect..................

• CFCs

• methyl bromide

• halogens

• halons

The angle between hydrogen and oxygen in water molecule is........................

• 104 degrees

• 104.5 degrees

• 120 degrees
• 90 degrees

What is the difference between base and alkali?

• Base is a type of acid, while alkali is a type of salt.
• Base and alkali are the same thing, just different names.
• Base is a substance that can donate protons, while alkali is a specific type of acid that is soluble in water.
• Alkali is a specific type of base that is soluble in water.

Who is the scientist that postulated that the thickness of ozone at STP is 3mm?

• Rutherford

• Dobson

• Bohr

• Mendeleev

From the endangered animals is.................................

• papyrus plant

• dodo bird

• barbary sheep

• dinasour

MgO is.............................oxide that dissolve in water forming...........................

• basic, H₂CO₃

• alkaline, MgOH

• basic, HCl

• basic, MgOH