Questions

Blood is a heterogeneous mixture because the blood cells are physically separate from the blood plasma. The cells have different properties than the plasma. The cells can be separated from the plasma by centrifuging, which is a physical change.

Veins are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart. In contrast to veins, arteries carry blood away from the heart.

Veins are less muscular than arteries and are often closer to the skin. There are valves in most veins to prevent backflow.

The usual cause of sea breeze is the difference in specific heat capacity between land and water Land heats and cools more quickly than water.

What is the cause of a sea breeze?

The air over the land is warmed and rises, to a greater temperature than that over the sea. This produces a convection current, with cooler air flowing in from over the sea to replace that rising from the land. At night the land cools more than the sea, so the action reverses to produce a land-breeze, blowing off the land.