(a) Read the following description of the element zinc and indicate which are physical properties and which are chemical properties. Zinc melts at 420 °C. When zinc granules are added to dilute sulfuric acid, hydrogen is given off and the metal dissolves. Zinc has a hardness on the Mohs scale of 2.5 and a density of 7.13 g/cm³ at 25 °C. It reacts slowly with oxygen gas at elevated temperatures to form zinc oxide, ZnO.

Video transcript

Hi everyone today. We have a question telling us that an unknown element was observed to have the following properties. One, it appears as a silvery liquid to it has a density of 13.53 g per centimeters cubed at room temperature three. It reacts with molecular iodine to produce a red solid Before it freezes at negative 38.83°C and boils at 356.73°C and five it forms a yellow solid when combined with dilute nitric acid, classify each property as physical or chemical. So, we need to remember some definitions here. Physical properties. We don't have to change the composition to observe chemical properties. We do have to change composition to observe. So now let's look at each of our options. It appears as a silver liquid. We don't have to change the composition to see that. So that is physical. two. It has a density of 13.53 g per cm cubed at room temperature. We don't have to change the composition to observe that. So it is physical. three. It reacts with molecular iodine to produce a red solid. We do have to change its composition to observe that because we are reacting it with another substance. So that is chemical before it freezes at negative 38.83 degrees Celsius. And boils at 356.73 degrees Celsius. We don't have to change its substance to have observed that. So that is physical. And lastly it forms a yellow solid one. Combined with dilute nitric acid. We are changing the composition there so that is chemical. And here are our answers. Thank you for watching. Bye.