📉  SCATTER PLOTS:

1) In your Science Notebook take notes on Scatter Plots.
2) After taking notes, complete Practice CAST Question below.
3) Then click Continue to complete the next section of notes.
4) Turn In: I will be stamping completed notes!

Scatter Plot Graphs

Scatter plots show relationships between two variables. On the CAST, you use them to decide if there is a positive, negative, or no correlation and to spot outliers.

Identify Variables & Correlation

Temperature vs. Reaction Rate

Question: "How does temperature affect the rate of this reaction?"

• Independent variable (x-axis): Temperature (°C)
• Dependent variable (y-axis): Reaction rate (units)
• Trend: The points go up from left to right (positive correlation).

Steps:

• Look for the overall pattern of the dots.
• Decide if it is positive, negative, or no correlation.
• Circle any outliers (points far from the pattern).

Scatter Plot: Temperature vs Reaction Rate

According to the data, as temperature increases, the reaction rate generally increases.

Show line of best fit

The purple point is an outlier because it does not follow the upward trend.

Notebook Task – Scatter Plot Notes

• Draw a mini version of the scatter plot. Use dots, not connected lines.
• Label the axes and write “positive correlation” next to the pattern.
• Circle the outlier and explain in one sentence why it is an outlier.
• Write a sentence that starts with “Based on the trend, if the temperature reached 55 °C, the reaction rate would probably...” (this is extrapolation).

Practice – CAST-Style Scatter Plot Questions

Use the scatter plot and the data table below.

Temperature (°C)	10	20	30	40	50	40 (trial 2)
Reaction Rate (units)	2	3	4	6	7	3

1. Does the data show a positive, negative, or no correlation between temperature and reaction rate?

Positive correlation, because the reaction rate tends to increase as temperature increases. Negative correlation, because the reaction rate tends to decrease as temperature increases. No correlation, because the points are randomly scattered. No correlation, because there is an outlier.

2. Which data point is an outlier, and what might explain it?

10 °C, 2 units, because low temperatures are always wrong. 30 °C, 4 units, because it is in the middle of the graph. 50 °C, 7 units, because it is the highest point. 40 °C, 3 units (trial 2), because it is much lower than the other rates near 40 °C and could be due to measurement error.

Check Answers

Continue to page 6

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