Determine the initial temperature of the water. You should extend your line of best fit on the graph.
How to approach this question
1. The "initial temperature of the water" corresponds to the temperature before any ammonium nitrate was added.\n2. This means you need to find the temperature when the mass of ammonium nitrate is 0 g.\n3. On your graph, extend the line of best fit backwards with a ruler so that it crosses the y-axis (the vertical line where x=0).\n4. Read the value where your line intercepts the y-axis. This is the initial temperature.
Full Answer
20.0 °C (or a value consistent with the student's line of best fit). By extending the line of best fit back to the y-axis (where mass = 0 g), the line intercepts the axis at 20.0 °C.
The initial temperature of the water is the temperature at the very beginning of the experiment, before any ammonium nitrate has been added. On the graph, this corresponds to a mass of 0 g on the x-axis. By extending the drawn line of best fit backwards (extrapolating), we can see where it intersects the y-axis. The line should cross the y-axis at 20.0 °C. This represents the starting temperature of the water.
Common mistakes
✗ Not extending the line back to the y-axis.\n✗ Misreading the y-axis scale.\n✗ Giving the temperature for the first reading (4.0 g) instead of for 0 g.
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