Fossils provide a window in Earth's history by showing us how they existed in the past. They can be dated through several ways and can show us how animals and plants have evolved over millions of years. Also, fossils can help us better understand ancient disasters by the inclusion of elements (such as <span>volcanic ash or dust from major space object impacts) and how they affected the life on earth)</span>
Answer:- The formula 
tells us that one formula unit of this compound is composed of one calcium atom, two nitrogen atoms, and six oxygen atoms.
Explanations:- Subscripts tell us about the number of atoms of the element for which they are used. For example, here the subscript of Ca is one, it means there is one calcium atom in the given one formula unit.
When we have subscripts inside and outside the parenthesis then they are multiplied and the outside subscript is considered for all the atoms present inside the parenthesis.
Here, for the given chemical formula, the subscript of N is 1 and the subscript present outside is 2. So, 1 x 2 = 2 and for oxygen, 3 x 2 = 6
So, we have one calcium atom, two nitrogen atoms and six oxygen atoms for one formula unit of given compound.
200 calories.
Explanation:
The (latent) heat of fusion of a material, is either one of:
1) the heat required to melt the material without
temperature change or
2) the heat removed from the material to freeze it
without temperature change.
For water this latent heat is 80 cal/g. Multiply this by
2.5 g to get 200 cal.
I suggest watching Martin Shkerli YouTube channel. He has a ton of videos on chemistry and is very helpful.
