Answer to Question 1
The relationship between seawater density and water temperature is that warm water has lower density and cold water has higher density.
Answer to Question 2
Newton's law of universal gravitation, which states that every object in the universe is attracted to every other object, states that the gravitational force is directly proportional to the produce of the masses of two bodies, but inversely proportional to the square of the distance between the two masses. Thus, although the Moon is very small (27 million times smaller in mass) compared to the Sun, it is much closer (390 times closer) and therefore exerts a stronger influence on Earth's tides. The solar bulges are only 46 the size of the lunar bulges, thus the Moon exerts just over two times the gravitational pull of the Sun on Earth's tides.