1. A 0.25kg piece of ice at -30°C is warmed by an electric heater and the following graph of the temperature is produced (I just redrew the graph). Assume that there has been no loss of energy to the surroundings.
a) use the information on the graph to determine the power output of the heater.
b) explain how long it will take to get the ice to the melting point 0°C.
c) explain how long it will take to melt completely once the ice reaches 0°C.
2. Q=m(c)(Δt). P=Q/t. Q=m(L). L is Latent heat of fusion, m is mass, Δt is change in temperature, t is time, Q is quantity of heat, P is power and c isspecific heat capacity.
3. So for a) I did, Q=m(c)(Δt). Q=0.25(2100)(-30-(-10)). Q=-10500. Now that I have Q, I can find the power. P=Q/t. P=-10500/150. P=-70W. Is this the correct power output of the heater? How can it be negative? Then for b) I assumed that if it took 150s for the ice to get 20 degrees warmer, it would only take 75s to get 10 degrees warmer, no? For c). To get the time it takes the ice to completely melt I did, Q=m(L). Q=0.25(330000). Q=82500. Actually for c) I have no idea what I'm doing. Scratch that, the entire question is super confusing. I would appreciate it if someone could really break this down for me as physics is definitely not my strongest subject. Thank you.
a) use the information on the graph to determine the power output of the heater.
b) explain how long it will take to get the ice to the melting point 0°C.
c) explain how long it will take to melt completely once the ice reaches 0°C.
2. Q=m(c)(Δt). P=Q/t. Q=m(L). L is Latent heat of fusion, m is mass, Δt is change in temperature, t is time, Q is quantity of heat, P is power and c isspecific heat capacity.
3. So for a) I did, Q=m(c)(Δt). Q=0.25(2100)(-30-(-10)). Q=-10500. Now that I have Q, I can find the power. P=Q/t. P=-10500/150. P=-70W. Is this the correct power output of the heater? How can it be negative? Then for b) I assumed that if it took 150s for the ice to get 20 degrees warmer, it would only take 75s to get 10 degrees warmer, no? For c). To get the time it takes the ice to completely melt I did, Q=m(L). Q=0.25(330000). Q=82500. Actually for c) I have no idea what I'm doing. Scratch that, the entire question is super confusing. I would appreciate it if someone could really break this down for me as physics is definitely not my strongest subject. Thank you.
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