Science experiments usually include an independent variable, dependent variable, and control. ... Science experiments also include something called constants. A constant is the part that doesn't change during the experiment.
Answer: C
Explanation:
Velocity is displacement over change in time. It’s a vector quantity, so velocity must include direction. You’re changing the direction, but the speed stays the same, because you are still going 20 km per hr
Answer:
Density = 7.87 grams per mL
Explanation:
Density is given by the formula:

where
Z = effective number of atoms in one unit cell.
M = Molecular mass of the substance
a = edge length of unit cell
Na = Avogadro number = 6.022×10²³
In this case:
Z=2 as it is body-centered type unit cell
M = 56 g per mole for iron
a = 287 pm = 
Substituting the above values in the density formula we get:

Density of iron is 7.87 grams per mL.
The first one is color change
Second is the precipitate present