They are a relatively recent invention.
I hope it was helpful for you.
Answer:

Explanation:
There are two main kinds of properties: chemical and physical.
Chemical properties, like the name suggests, have to be observed by changing the chemical composition.
That leaves <u>physical properties.</u> They can be measured without any chemical composition changes.
Some examples include: color, odor, mass, density, and volume. All can be measured with just the senses or measuring tools and no composition alterations are needed.
Answer:
MgBr2 < MgCl2 < NaBr < NaCl
Explanation:
In order to determinate ionic character, we have to subtract the electronegativity from the elements involved. This is known as Pauling rule.
MgBr2 > ΔΕΝ = 1.8
NaCl > ΔΕΝ = 2.3
MgCl2 > ΔΕΝ = 2
NaBr > ΔΕΝ = 2.1
You just need to multiply the total mass by the decimal value of the part that is tin. 133.8*0.103=13.8g (following the rules of significant figures).