Zinc is an element that can chemically react with other substances. When zinc reacts with hydrochloric acid, zinc chloride is produced. Which observation best supports the conclusion that a chemical reaction has occurred between zinc and the acid? *

In which situation can a mixture always be called a solution

Name the element in group 17, period 2. (periodic table)

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?