Answer: Hot air is less dense than cool air; the heated air causes the balloon to rise simply because it is lighter than an equal volume of cold air. Buoyancy is an upward force that the air exerts, and it helps hot-air balloons and blimps stay in the air. A hot air balloon uses a burner to heat up the air inside the balloon.
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Answer:
Friction produces heat because it causes the molecules on rubbing surfaces to move faster and have more energy.
Explanation:
Science
Freshwater does not contain any salt, salt water does however contain salt.
You didn't put any answer choices, but air and water are generally the greatest.
Explanation:
With continual improvements made to microscopes over time, magnification technology advanced enough to discover cells in the 17th century. This discovery is largely attributed to Robert Hooke, and began the scientific study of cells, known as cell biology.
