Answer:
B
Explanation:
A chemical change occurred, and this caused the liquid’s physical properties to change.
when we read her experiment we can see that color changed to blue, it is because new products are formed. And the temperature cause this.
Answer:

Explanation:
Subscripts are numbers written after elements, subscripts indicate how many of each atom there are in a compound.
Answer: Option (4) is the correct answer.
Explanation:
It is known that density is mass divided by volume.
Mathematically, Density = 
Since, density is directly proportional to mass. So, more is the mass of an element more will be its density.
Mass of magnesium is 24.305 g/mol.
Mass of barium is 137.327 g/mol.
Mass of beryllium is 9.012 g/mol
Mass of radium is 226 g/mol.
Hence, radium has more mass therefore it will have the greatest density at STP.
The density in kg/m³ = 1.14 x 10⁴
<h3>Further explanation </h3>
Density is a quantity derived from the mass and volume
Density is the ratio of mass per unit volume
With the same mass, the volume of objects that have a high density will be smaller than objects with a smaller type of density
The unit of density can be expressed in g/cm³ or kg/m³
Density formula:

ρ = density , g/cm³ or kg/m³
m = mass , g or kg
v = volume , cm³ or m³
A density of Lead : ρ = 11.4 g/cm³
the density in kg/m³ :
