Some examples of physical changes are:
Breaking a glass
Chopping wood
Tearing paper
Mixing sand and water
Melting an ice cube
These all are physical changes because the composition of the matter does not change.
20 mol of NH, can be produce from 30 mol o H2
To calculate the average mass of the element, we take the summation of the product of the isotope and the percent abundance. We calculate as follows:
Average atomic mass = .374 ( 184.953 amu ) + .626 ( <span>186.958 amu ) = 186.208 amu
Hope this answers the question. Have a nice day.</span>
Answer:

Explanation:

Data:
Mass of NaCl = 4.6 g
Mass of water = 250 g
Calculations:
Mass of solution = mass of NaCl + mass of water = 4.6 g + 250 g = 254.6 g.

Answer:
The correct answer is that it is made of atoms that are covalently bonded together.
Explanation:
Hope this helped Mark BRAINLEST!!!