# Homework Help: Heat - What is the temperature of this object?

1. Oct 3, 2008

### MIA6

If 1 kilogram of solid X at -20C gains 40 kilojoules of energy, its temperature will be ____
1) -120 2) -80 3) -20 4) 80
Given: Specific heat of solid: 0.4, heat of fusion: 60, melting point:-20,
So I did: mL+40=0.4(T+20) --> 60+40=0.4(T+20), T=230. But no choice for that.

Then I have one question, is there any way to tell if a substance is solid or liquid or gas, in other words, what phase? because there is a diagram with temperature on y-axis, time on x-axis, so how can I tell what phase a certain point is.

Thank you.

2. Oct 3, 2008

### hage567

Re: heat

Can you specify the units that are attached to these quantities? I think you might need to convert to grams to do this properly but I can't tell without the units.
Well, you can pick out where the phase changes occur since the temperature will not change during that time interval.

3. Oct 4, 2008

### Andrew Mason

Re: heat

I am not sure what you are doing.

First of all, you have to determine where the phase change will occur and how much energy is needed to achieve it. At what temperature does the solid melt? What happens to temperature during that phase change? Is there enough heat to complete the phase change?

AM