The diameter of the He He atom is approximately 0.10 nm nm . Calculate the density of the He atom in g/cm 3 g/cm3 (assuming that it is a sphere).

Explanation:

Density is defined as the ratio of mass per unit volume of a substance.

Density = Mass/Volume

Since the shape of the Helium atom is a sphere, we will use the formula for calculating the volume of a sphere to get the volume of helium

Volume of a sphere = 4/3πr³ where r is the radius of the sphere.

Given the diameter of the sphere = 0.10nm

radius of the sphere = 0.10/2 = 0.05nm = 5*10⁻⁹cm

Volume of the sphere = 4/3 * 3.14 * (5*10⁻⁹)³

V =  4/3 * 3.14 * 125*10⁻²⁷

V = 1,570*10⁻²⁷/3

V = 523.33*10⁻²⁷

V =  5.233*10⁻²⁵cm³

Mass of the Helium atom = 6.6464731 × 10⁻²⁴ g

Density of the Helium atom in g/cm³ = 6.6464731 × 10⁻²⁴ g/5.233*10⁻²⁵cm³

Density of the Helium atom in g/cm³ = 1.27 * 10⁻²⁴⁻⁽⁻²⁵⁾g/cm³

Density of the Helium atom in g/cm³ = 1.27 * 10⁻²⁴⁺²⁵g/cm³

Density of the Helium atom in g/cm³ = 1.27 * 10¹g/cm³

Density of the Helium atom in g/cm³ = 12.7g/cm³

Hence the density of the He atom in g/cm³ is 12.7g/cm³

the molecules move in straight line until they collide with each other or with the walls of the container. collisions are perfectly elastic; when two molecules collide, they change their directions and kinetic energies, but the total kinetic energy is conserved.

explanation:

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.