Answer:
C. Its physical structures
Explanation:
A dichotomous key is defined as a tool used to differentiate between objects and organisms. A dichotomous key consist of series of question related to the species and at the end gives the scientific name of the species.
The characteristic that is most helpful when identifying organism using a dichotomous key is "Its physical structures". for example: if a person want to identify a tree, a dichotomous key ask about the physical structures such as if the tree has needles or leaves.
So, physical structures are most helpful while using a dichotomous key.
Answer:
1.24 × 10²⁵ molecules of oxygen gas
Explanation:
Step 1: Given data
Moles of oxygen gas: 20.6 moles
Step 2: Calculate the number of molecules present in 20.6 moles of oxygen gas
In order to convert moles to molecules, we need a conversion factor. In this case, we will use Avogadro's number: there are 6.02 × 10²³ molecules in 1 mole of molecules.
20.6 mol × 6.02 × 10²³ molecules/1 mol = 1.24 × 10²⁵ molecules
The correct answer is:
D) a chemical change produces a new substance by breaking and forming new bonds
Density = mass / volume
0.601 = m / 7.25
m = 0.601 x 7.25
m =4.35725 g
hope this helps!