The nanotubes measure only a nanometer in diameter. A single perfect nanotube is 10 to 100 times stronger than steel and has electrical properties. A) B) C VFV VVF) VVV D) FVV 29 E) FFV. Point to true propositions (V) or false (F) as appropriate: fuel cells are electrochemical devices that continuously transform energy chemical a fuel (hydrogen) and oxidant (oxygen) into electrical energy. Fuel cells differ from a pile because they do not store energy. Fuel cells produce a clean energy that does not harm the environment and is silent.

A) B) C VFV VVF) D) FVV E) FFV 30 VVV. Point to true propositions (V) or false (F) as appropriate: the The polyvinyl chloride and polystyrene are examples of homopolymers. Thermoplastic polymer softens when heated while a thermosetting polymer hardens (to high temperatures can decompose). There are a large amount of A polymer in nature) VVV B) VVF C) FVV D) VFF E) FFF 31. Point to true propositions (V) or false (F) as appropriate: plasma is the State in which there is electrical loads neutralized each other. They are natural examples of plasma; the rays, the solar winds. Examples of artificial plasmas are not known.

A) B) C VFV VVF) VVV D) FVV 32 E) FFV. Point to true propositions (V) or false (F) as appropriate: plasma It is a State of matter that can only be appreciated in laboratory experiments. Industrial application of plasma is called plasma cutting based on raise the temperature of the material to be cut in a highly localized manner and over 30 000 C, carried the material to the plasma state. Another commercial application of plasma are the so-called plasma screens. A) VVF B) VFV C) VVV D) FVV E) FFV original author and source of the article.