Which describes the substances that form covalent bonds

In saturated organic compounds, all the bonds between carbon atoms are called?

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?

How does kepler second law of planetary motion overthrow one of the basic beliefs of classical astronomy