Class: 7th
3. Water is not an element.
4. An airship is filled with helium.
5. Copper is used to make wirers.
Answers
Answer:
3. Of the four elements of the ancients, water is the only one which is a pure chemical substance, albeit a compound and not an element. ... The discovery that water is a compound of hydrogen and oxygen (or, in the terminology of the day, of inflammable air and dephlogisticated air) was made in the early 1780s.
4. The airship is filled with a lifting gas (Helium). The atmospheric air has a higher specific weight than the lifting gas. The airship envelope filled with the light gas generates a lift that is equal to the weight of the displaced air and the airship floats in the heavier air.
5. Copper electrical wires are safer to use than wires made of most other conductive metals because they are resistant to heat. As you can see, copper is the preferred metal for electrical wires for several reasons. It has high electrical conductive; it's inexpensive; it's ductile; and it's thermal resistant.