a.) what is the name of the phase change that occured?

b.) at what temperature did the phase change occur?

c.) how long did the phase change occur?

d.) during the phase change is heat leaving the object, entering the object, or neither?

e.) how long was the object completely liquid?

Question

a.) what is the name of the phase change that occured?

b.) at what temperature did the phase change occur?

c.) how long did the phase change occur?

d.) during the phase change is heat leaving the object, entering the object, or neither?

e.) how long was the object completely liquid?

Accepted Answer

### Part a)
# Brief Explanations:
The graph shows a temperature - time curve where temperature remains constant for a period (latent heat phase) and overall temperature is decreasing. When a substance changes from liquid to solid (freezing) or gas to liquid (condensation), but here since temperature is decreasing and there's a flat line (constant temperature during phase change), and if we consider the cooling process, the phase change here is freezing (if it was a liquid cooling to solid) or condensation (gas to liquid), but more likely freezing (as the temperature is going from higher to lower and the flat part is the freezing point). The phase change where a liquid turns to solid is freezing.
# Answer:
Freezing (assuming the substance was liquid before, and the flat line is the freezing point during cooling)

### Part b)
# Explanation:
## Step1: Identify the flat part of the graph.
The flat part of the temperature - time graph (where temperature doesn't change) is between time 20 min and 60 min (or so). The temperature at this flat part is the temperature of the phase change. From the graph, the y - axis (temperature) at the flat line is 175 (looking at the grid, between 150 and 200, the flat line is at 175? Wait, no, looking at the graph, the flat line is at 175? Wait, the graph has 200, 150, 100. Wait, the flat line is between 20 min and 60 min, and the temperature there is 175? Wait, no, the vertical grid lines: at time 20, the temperature is 175? Wait, the graph shows that at time 20, the temperature drops to a flat line. Let's check the y - axis: 250, 200, 150, 100. The flat line is at 175? Wait, no, maybe it's 175? Wait, no, looking at the graph, the flat part is at 175? Wait, no, the user's graph: the first segment goes from (0, >250) to (20, 175), then flat until (60, 175), then down to (100, 100). So the temperature during phase change is 175 $^\circ$C? Wait, no, maybe I misread. Wait, the y - axis is Temperature (Cels), with 250, 200, 150, 100. The flat line is at 175? Wait, no, the point at time 20 is at 175? Wait, the vertical line at time 20, the temperature is 175 (between 150 and 200). So the temperature of the phase change is 175 $^\circ$C. Wait, maybe it's 175, but let's check again. The graph: from time 0 to 20, temperature decreases from above 250 to 175, then stays at 175 until time 60, then decreases to 100 at time 100. So the temperature of the phase change is 175 $^\circ$C.
## Step2: Confirm the temperature from the graph.
The flat region (where phase change occurs) has a constant temperature. From the graph, the y - value of the flat line is 175 $^\circ$C (assuming the grid is such that between 200 and 150, the flat line is at 175).
# Answer:
175

### Part c)
# Explanation:
## Step1: Find the start and end time of the flat part.
The phase change occurs during the flat part of the temperature - time graph. The start time of the flat part is 20 min, and the end time is 60 min.
## Step2: Calculate the duration.
Duration = end time - start time = 60 - 20 = 40 min.
# Answer:
40

### Part d)
# Brief Explanations:
During a phase change like freezing (liquid to solid) or condensation (gas to liquid), heat is leaving the object. Because for freezing, the liquid loses heat to become a solid (exothermic process). So heat is leaving the object.
# Answer:
Heat is leaving the object

### Part e)
# Explanation:
## Step1: Determine when the object is completely liquid.
Before the phase change (freezing) starts, the object is liquid. After the phase change ends, the object is solid. Wait, no: if the phase change is freezing (liquid to solid), then before the phase change (time 0 to 20 min), the object is liquid (cooling down). During the phase change (20 - 60 min), it's changing from liquid to solid. After 60 min, it's solid (cooling down). Wait, no, maybe the phase change is freezing, so the time when it's completely liquid is before the phase change starts? No, that doesn't make sense. Wait, maybe the object was liquid, then starts to freeze at 20 min, and is completely liquid before 20 min? No, the first segment is cooling of liquid. Then at 20 min, it starts to freeze (phase change). So the time when it's completely liquid is from time 0 to 20 min? No, that can't be. Wait, maybe I got the phase change wrong. If the phase change is freezing (liquid to solid), then the time when it's completely liquid is before the phase change (0 - 20 min) and during the phase change, it's a mixture of liquid and solid. Wait, no, the question is "how long was the object completely liquid". So before the phase change (freezing) starts, the object is liquid. The phase change starts at 20 min, so the time from 0 to 20 min is when it's liquid (cooling), and then during 20 - 60 min, it's freezing (liquid and solid), and after 60 min, it's solid. Wait, but that would be 20 min, but that seems short. Wait, no, maybe the phase change is melting? No, because the temperature is decreasing. If the temperature is decreasing, it's cooling, so phase change is freezing (liquid to solid) or condensation (gas to liquid). If it's freezing, then the time when it's completely liquid is before the phase change (0 - 20 min) and during the phase change, it's a mixture. But the question is "completely liquid". So maybe the time from 0 to 20 min is when it's completely liquid (cooling liquid), then from 20 - 60 min, it's freezing (liquid and solid), then from 60 - 100 min, it's solid (cooling solid). So the time when it's completely liquid is 20 min? But that seems wrong. Wait, maybe I misread the graph. Wait, the first segment: from (0, T1) to (20, T2), where T2 is the freezing point. So the time when it's completely liquid is 20 min (from 0 to 20 min). But that seems too short. Wait, no, maybe the phase change is from gas to liquid (condensation), but the temperature is decreasing, so gas cooling to liquid. Then the time when it's completely liquid would be after condensation? No, this is confusing. Wait, let's re - examine the graph. The temperature starts high, decreases to a flat line (phase change temperature), then decreases again. The flat line is the condensation or freezing temperature. If we assume it's freezing (liquid to solid), then the time when the object is completely liquid is the time before the phase change starts, which is from 0 to 20 min (20 min), and then during the phase change (20 - 60 min), it's a mixture, and after 60 min, it's solid. But the question is "how long was the object completely liquid". So the answer is 20 min? Wait, no, maybe the time from 0 to 20 min is 20 min, but that seems short. Wait, maybe the graph's first segment is from 0 to 20 min (20 min), then phase change from 20 to 60 min (40 min), then cooling from 60 to 100 min (40 min). So the time when it's completely liquid is 20 min? But that doesn't seem right. Alternatively, maybe the object was liquid, and the time when it's completely liquid is the time before the phase change, which is 20 min. But I think there's a mistake in my reasoning. Wait, maybe the phase change is melting? No, because the temperature is decreasing. Melting is when temperature increases. So it's freezing. So the time when it's completely liquid is 20 min (from 0 to 20 min).
# Answer:
20 (assuming the time from 0 to 20 min is when it's completely liquid, before the phase change starts)

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QUESTION IMAGE

Question

Explanation:

Part a)

Step1: Identify the flat part of the graph.

Step2: Confirm the temperature from the graph.

Step1: Find the start and end time of the flat part.

Step2: Calculate the duration.

Answer:

Part b)