Answer: <u>Mixtures can be physically separated but pure substances cannot be physically separated.</u>
Explanation: Mixtures can be physically separated by using methods that use differences in physical properties to separate the components of the mixture, such as evaporation, distillation, filtration and chromatography. A pure substance, any compound or element, can't be separated into different atoms by physical methods. Pure substances are compounds and elements (made up of the same atom or same molecule respectively), while mixtures are an assortment of different substances put together. Hope this helps ^-^.
Density of unit cell is mathematically expressed as
D =
where, Z = number of atoms/unit cell = 4 (For FCC structure)
Atomic weight of Cu = 63.5 g
a = edge length = 351 pm = 351 X 10^-10 cm
Avagadro's number = 6.023 X 10^23
∴ Density of unit cell =
= 9.752 g/cm3
Now, for FCC structure a = √8 r
where r = radius of Cu
∴ r = a/√8 = (351 X 10^-10)/√8 = 1.24 X 10^-8 cm = 124 pm
It would be "Protons have positive charges"