energy
Oxygen, Hydrogen, Helium, and many other gases.
Elements are commonly referred to as the basic building blocks of all matter. This is because you cannot break them down any further and still maintain a whole atom. Once an element is broken down, you have protons and neutrons.
Actually Every part of the computer is seen and can touch called the Hardware. Software is the Intangible.
1st state of matter- solid 2nd state of matter- liquid 3rd state of matter- gas 4th state of matter- plasma 5th state of matter- Bose Einstein condensate 6th state of matter - fermionic condensate 7th state of matter- thought to be Fermionic condensate
Physical models can be seen and touched
Yes, it is possible to connect a computer straight to a network cable which usually connects the modem. Look for the cable at Ebay.
emotions
energy
A vacuum is not visible, as it is an absence of matter. Matter must exist to be seen, and so a vacuum cannot be seen.
Ultraviolet rays cannot be seen or felt. Ever had a sun-burn? I say UV rays can be felt.
A mirage or hallucination, maybe?
Energy
Yes, matter can be something that you can not see. This is because one form of matter is gas, which can not be seen.
'Time'.
darkness or emptiness?
Yes, that is true. About half of the sun's energy comes to the Earth as infrared radiation.
heat
Yes this is true. We have recently discovered dark matter exists with the help of the Hadron particle collider, but can not see dark matter. (not yet any way)