7. Calculate the amount of energy required heat 100.g to the following: a. H2O(s) changes to H2O(l) at 0°C b. H2O(l) changes to H20 (s) at 0°C c. H2O(l) at 10°C changes to H2O(l) at 20°C

a=b=33400 J

c=4180 J

Further explanation

Heat can be calculated using the formula:  

Q = mc∆T  

Q = heat, J  

m = mass, g  

c = specific heat, joules / g ° C  

∆T = temperature difference, ° C / K  

The heat to change the phase can be formulated :

Q = mLf (melting/freezing)

Q = mLv (vaporization/condensation)

Lf=latent heat of fusion

Lv=latent heat of vaporization

The heat of fusion for water at 0 °C : 334 J/g and the heat of vaporization at 100 °C : 2,230J/g

a. melting

b. freezing

c.raise the temperature(c water = 4.18 J/g C)

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.

the number of protons in the nucleus of a given element. has slight luster and conducts electricity at high temperatures like metal.but like a nonmetal,boron is brittle and does not conduct electricity well at low temperatures. in graphite, carbon is a soft,brittle solid.it is reflective,ductile,or malleable.