Can something be invisible and still be made of matter ? explain...

When combined with Hubble's visible-light data, astronomers can ... Dark things absorb light, but this invisible stuff neither absorbs, nor ... Is dark matter made of still undiscovered tiny particles, as most physicists suppose?

Explanation:

Yes, air is a great example, air is made of matter and yet we do not see it.

level 4 to level 2 : ))

weight of any object is given by

w = m*g

where m is mass of the object and g is the acceleration due to gravity.

for earth the value of g is 9.8 m/s^2 so

w=117.6 n m=12 g=?

117.6=12g => g=9.8 m/s^2

which is the force of gravity on earth.