The density of liquid water is fairly constant across the range of temperatures. Liquid water is most dense at 4°C. At temperatures below that, water will expand slightly. When water freezes to form ice, it expands. Water vapor (steam) expands when heated.
Sink.
The formula to calculate the density of water for a change in temperature is: Density = Density at reference temperature / [1 - β (T - T_ref)], where β is the volumetric thermal expansion coefficient of water, T is the temperature, and T_ref is the reference temperature.
The most common thing that would be a gram is a mL of water. That is, it is waters maximum density, temperature and purity will change that.
Oil is heavier than water so it sinks to the bottom.
Salinity (how much salt) of the water and low temperatures
An object will sink if its density is greater than the fluid it is placed in, and it will float if its density is less than the fluid. Density is a measure of how much mass is contained in a given volume, so comparing the density of an object to the density of the fluid it is in helps predict its buoyancy.
Density
Changing the shape CAN change the density. If you change it into a smaller shape, then you increase the density. However the mass will not change.
Density is a physical property.
The temperature of the water and the salt content of the water.
To change density there are three ways. You can change the shape, mass or volume of the object
It won't change. Density is volume divided by mass, so if volume doesn't change, density doesn't change unless you change the mass of the object.