What is ammonium hydroxide $(NH_4OH)$?

Which of the following properties is generally not shown by metals?

Give two examples each of metals that are good conductors and poor conductors of heat,respectively.

Which of the following metals is used for making jewelry?

$(a)$ Why does calcium start floating when added to water?
$(b)$ Most metals do not release hydrogen gas when reacting with nitric acid. Why?
$(c)$ Write the chemical equation for the reaction of iron with steam. Name the compound of iron obtained.

Name two metals which react with dilute $HNO_{3}$ to evolve $H_{2}$ gas.