Answer:
41.8g
Explanation:The equation for working out the amount of thermal energy required is q=mcΔT, where q is the amount of energy, m is the mass being heated up in grams, c is the specific heat capacity of what you're heating up in joules per gram per kelvin, and ΔT is the change in temperature in degrees Celsius or Kelvin (technically it should be in Kelvin but for a change in temperature, Celsius is the same as Kelvin).In this case, the mass is 2.0g, the specific heat capacity of water is 4.18J/g/K, and the change in temperature is 5.0°C=5K, therefore the energy needed to raise it is: 5×2×4.18=41.8J.This is only theoretical though, in the real world a lot of heat would be lost to the surroundings, so it would require more energy than this.