Question

What are the chemical and physical properties of calcium that are described in the following paragraph?

Calcium is a shiny, silvery-white metal. When it is exposed to moist air, it readily tarnishes. At room temperature, calcium exists in the solid state and its melting point is 842 C. It reacts with acid and with water to yield hydrogen gas.

Answer 1

Shininess and silvery-white are physical properties.

Readiness to tarnish is a chemical property.

States and the melting point are physical properties.

Reactions are chemical properties.

Explanation:

I'll just start off with the definitions of physical and chemical properties, and what you can look for when identifying either one.

Physical Properties

Anything that can be observed without creating or destroying anything new.

The most common example would be a physical description (appearance). As a rule of thumb, any changes of states are physical reactions, and therefore any melting points, boiling points or freezing points are physical properties.

I'm not going to go any more in-depth as to why, but just remember that.

Chemical Properties

Anything that can be observed through a reaction, in which the identity or original matter is changed.

The most common example would be oxidation. Again, another rule of thumb here would be that cannot be reverted is a chemical reaction. For example, lighting a match would be a chemical reaction because you can't 'unburn' the match (in general, anything to do with fire is a chemical property).

Now onto the actual question:

"Calcium is a shiny, silvery-white metal."

This is a physical description. Probably the easiest one here, it is obviously a physical property, as it is simply a description that can be attained by just looking.

"When it is exposed to moist air, it readily tarnishes."

I'm assuming here that tarnishing means corrosion. Corrosion is a chemical reaction, therefore this is a chemical property of calcium. Think about it this way—you can't 'untarnish'/'unrust' a metal that has been corroded.

"At room temperature, calcium exists in the solid state and its melting point is 842 C."

The reason this is a physical property has to do with the arrangement of atoms, but I won't explain that here. Just know that anything to do with phase/state changes are physical reactions, and thus, this is a physical property.

"It reacts with acid and with water to yield hydrogen gas."

Another easy one. This reaction is producing something new, something that hadn't existed before. Because it is creating something new, it is a chemical reaction—a chemical property of calcium.