Jupiter's core has a temprature of 4273k so being a gas giant why it has a surface temp -140 Cels.?

Answer 1

"Temperature at 1 bar: 165 K (-108 C)

Temperature at 0.1 bar: 112 K (-161 C)" (1)

"The temperature and pressure inside Jupiter increase steadily toward the core. At the phase transition region where liquid hydrogen (heated beyond its critical point) becomes metallic, it is believed the temperature is 10,000 K and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K and the interior pressure is roughly 3,000–4,500 GPa." (2)

All of these temperatures are necessarily calculated from what has been observed of Jupiter's upper atmosphere, and assumptions about the probable interior construction of the planet.