IB DP Chemistry: SL复习笔记11.2.5 Drawing Graphs

Drawing Graphs

General guidance on drawing graphs

  • Graphs need to have:
    • Clear title
    • Labelled axes
    • Units on the axes
    • Appropriate linear scales without any jumps
      • This means the plotted graph must occupy at least half or more of the sheet or grid
      • A rough rule of thumb is that if you can double the scale and still fit all the points on, then your scale is not appropriate
    • Clearly shown data points
      • The most common convention is to use small crosses to show the data points

Graph of concentration versus time

5.6-Reaction-Kinetics-Step-1-graph

Graphs must shows appropriate scales, labelling and units. The independent variable usually goes on the x-axis and the dependent variable on the y-axis

  • Remember the independent variable is the one you control or manipulate and the dependent variable is the one that changes as a result of your manipulation
  • Always draw data points in pencil as it  makes it easier to make corrections and adjustments

Best Fit Lines

  • Students often confuse the term lines of best fit with straight lines
  • Lines of best fit can be straight lines or curves (just like the example above) and:
    • They show the trend of the data
      • It does not have to go through all the points, but shows the general trend
    • They must go through the majority of the points
    • Where the data is scattered the points should be evenly distributed on either side of the best fit line
  • Sometimes the best fit line has to be extended to find a value from a graph
    • This is called extrapolation as this example shows from a temperature correction graph in a calorimetry investigation where the cooling section is extrapolated to find the maximum temperature rise:

5.1.4-Temperature-correction-graphs

Extrapolation on a temperature correction graph

  • Interpolation is the term used to describe the process of assuming a trend line applies between two points as this example below shows:

Substrate-concentration-and-rate-of-reaction-1

The difference between extrapolation and interpolation on a graph

Exam Tip

You will have to decide if the origin, point (0,0) should be included as a data pointIf it does, it will be a good place to anchor the graph as it will be the most accurate data point

 

 

 

 

 

转载自savemyexams

更多IB课程
翰林国际教育资讯二维码