it is mars it has water
I assume you mean "planet". That would be Venus.
No, the gravity of this planet will not be greater than that of earth. If the new planet has a mass equal to that of earth, its total gravity will be the same. There is a little ambiguity regarding 4 times earth density and half the earth's diameter if the idea is to keep the mass of this proposed planet the same as the earth. But setting that aside and assuming that the mass of the new planet is the same as earth's, the gravimetric field will be the same. Gravity is proportional to mass, and identical mass yields identical gravity. Now to the good part! The surface gravity of the new planet will be considerably higher than the surface gravity of earth. Both planets have the same mass and the same gravity, but a person standing on the surface of the new planet will be experiencing a whole lot more force pulling on him. All the mass of the new planet is beneath this person, but he's a lot closer to the center of gravityand will weigh a whole lot more.
Volume increases with the Cube of the radius, so an easy way to compute the volume of the giant planet is to simply take the ratio of the radius Giant Planet: Earth and raise it to the 3rd power.Since these planets are the same shape (Spherical) this ratio is accurate enough for our purposes. In the case of an object that is oblate (like Saturn or Jupiter), one can still calculate the volume accurately by taking the Equatorial Radius squared and multiplying it by the Polar Radius.In this given case the volume of Giant Planet = 14 x 14 x 14, or 2,744x that of Earth.Since Mass = 681x that of Earth, Density = 681/2744 = 0.248 of Earth's (just a little under one quarter).You could go one step further to calculate the density of this object by multiplying the density ratio by Earth's density (5.515x water) - so Giant Planet's density = 1.369 grams/cm3.
Mercury. Whilst it is not the most dense (Earth being the most dense planet of the Solar System), without gravitation compression on the Earth, Mercury would be the most dense. So if Earth was the same size as Mercury, Mercury would be the densest planet. It is also the smallest planet.
That's because Mars has an axial tilt which is almost the same as the Earth's. A planet's axial tilt is the most important factor in determining the seasons.
Venus has almost the same mass as Earth.
Earth.
Venus because it is almost the same size as Earth.
Mercury is only slightly less dense than Earth.
They both have an iron core, and they have the same density.
mars
If the planet is smaller, then it can't have the same size. If you assume that a smaller planet has the same density as Earth (and therefore less mass), its surface gravity will be smaller. If you assume that a smaller planet has the same mass as Earth (and therefore more density), its surface gravity will be greater. This is because we would be closer to the planet's center - or to the planet's matter in general.
Venus, it is slightly smaller, and much hotter
The moon's average density is about the same as the density of mantle of the Earth.
it's almost the same ... but earth's is a little bit more
I assume you mean "planet". That would be Venus.
We think it can. The earth's average density is more than 5.5 times the density of water, which we think qualifies as "lots of density". Also, the earth has a mass of 5,970,000,000,000,000,000,000,000 kilograms, which we really think is lots of mass.