Answer:
Incase you have H and F and another H and F
Answer:
This is because it is a physical change not a chemical change.
A sodium atom changes into a sodium ion by losing electrons. When an atom loses an electron, it's number of protons and electrons are not balanced. When an atom loses an electron (negative charge) it becomes more positive. Hopefully this helps!
<u>Answer:</u>
<em>The amount of energy needed when water at 72 degrees c freezes completely at 0 degrees c is
Joules</em>
<em></em>
<u>Explanation:</u>

where
= Final T - Initial T

=30125J
Q is the heat energy in Joules
c is the specific heat capacity (for water 1.0 cal/(g℃)) or 4.184 J/(g℃)
m is the mass of water
mass of water is assumed as 100 g (since not mentioned)
is the heat energy required for the phase change
=mass × heat of fusion

Total heat =
Total Heat = 30123J + 33600J
= 63725 J
=
Joules is the answer