Water is one of the few substances which expand in volume when frozen, compared to liquid. Usually substances condense when cooled, but at the point of freezing, when liquid water becomes solid ice, the molecules lock into a matrix in which there is more space between molecules - ice expands! This is why ice floats on liquid water.
It is this miracle which has shaped the planet and allowed life to thrive. Expansion of ice is responsible for much land-shaping erosion on land, the heaving off of boulders from mountain tops. And the floating of ice on lakes, rivers and oceans - if the frozen water was indeed more dense than liquid water, it would sink and pile up in the cold depths. There would be no life thriving under the ice, overwintering. It would all eventually freeze solid, and all the life forms with it.
As temperature increases, the average kinetic energy of a sample of gas molecules decreases.
Answer:
Because: The mixtures contain unwanted substances which may be harmful and may degrade the properties of mixtures. So we, need to separated them and extract useful substances.
Answer:
2.79 °C/m
Explanation:
When a nonvolatile solute is dissolved in a pure solvent, the boiling point of the solvent increases. This property is called ebullioscopy. The temperature change (ΔT) can be calculated by:
ΔT = Kb*W*i
Where Kb is the ebullioscopy constant for the solvent, W is the molality and i is the van't Hoff factor.
W = m1/(M1*m2)
Where m1 is the mass of the solute (in g), M1 is the molar mass of the solute, and m2 is the mass of the solvent (in kg).
The van't Hoff factor represents the dissociation of the elements. For an organic molecule, we can approximate i = 1. Thus:
m1 = 2.00 g
M1 = 147 g/mol
m2 = 0.0225 kg
W = 2/(147*0.0225)
W = 0.6047 mol/kg
(82.39 - 80.70) = Kb*0.6047*1
0.6047Kb = 1.69
Kb = 2.79 °C/m
Answer:
Single-celled organisms use cell division as their method of reproduction. Cell Division and Growth: A sea urchin begins life as a single cell that (a) divides to form two cells, visible by scanning electron microscopy.
Explanation:
Los organismos unicelulares utilizan la división celular como método de reproducción. División y crecimiento celular: un erizo de mar comienza su vida como una sola célula que (a) se divide para formar dos células, visibles mediante microscopía electrónica de barrido.
