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Worksheet Grade 6 Art & Music

Cold Water Below Delacourt Dam: A Diverging Palette for a River Map

Grade 6 students find the median and quartiles of fictional river temperatures below a dam, then use them to design a color-blind-safe diverging palette and legend.

Objectives

  1. Students will find the median, quartiles, and interquartile range of a set of river temperature readings.
  2. Students will use those measures to set the color classes of a diverging palette for a map.
  3. Students will justify palette decisions about warm and cool hues, value, a neutral midpoint, and color-blind readers.

Vocabulary

Key words: diverging palette, hue, value, neutral, legend, median, quartile, interquartile range

Teacher overview

Many dams release water from deep in their reservoirs, where the water stays cold even in summer, so the river just below such a dam can run much colder than the river farther downstream. Temperature matters to river life because cold water holds more oxygen than warm water. In this worksheet, a stream team has measured the temperature at eleven stations along the Marrin River below the fictional Delacourt Dam, and students design the colors for a map of those readings. Map designers use a diverging palette when the data has a meaningful middle: one family of hues shows values below the middle, a second family shows values above it, and a light neutral marks the middle itself. Students first find the median and quartiles, then use them as the palette's class breaks and make the hue, value, and legend decisions. A common misconception is that more colors, or a full rainbow, make a map more informative; a rainbow has no clear middle and no steady order from light to dark, so readers cannot tell at a glance which stations are far from typical.

Cold Water Below Delacourt Dam: A Diverging Palette for a River Map — Grade 6 Art & Music
Name: ____________________________ Date: ______________

Student Worksheet

In our scenario, the Marrin River flows out of the fictional Delacourt Dam. A stream team measured the water temperature at 11 stations on one summer afternoon. Station 1 is just below the dam. Station 11 is the farthest downstream. A cold, spring-fed creek joins the river just above Station 7. You will design the colors for a map of these readings.

Station 1 2 3 4 5 6 7 8 9 10 11
Temperature (°C) 9 10 12 13 15 16 13 17 18 19 21

The 11 readings are 9, 10, 12, 13, 15, 16, 13, 17, 18, 19, and 21 degrees Celsius.

  1. Put the 11 readings in order from least to greatest. What is the median temperature?
  2. The lower quartile is the median of the five readings below the median. What is the lower quartile?
  3. The upper quartile is the median of the five readings above the median. What is the upper quartile?
  4. What is the interquartile range, the upper quartile minus the lower quartile?

The map uses five color classes. The breaks come from the quartiles and the median.

Color class Temperatures in the class
Dark blue 12 °C or colder
Light blue 13 °C or 14 °C
Light gray 15 °C
Light orange 16 °C or 17 °C
Dark orange 18 °C or warmer
  1. How many of the 11 stations are colored dark blue, at 12 °C or colder?
  2. How many of the 11 stations are colored dark orange, at 18 °C or warmer?
  3. Station 7 reads 13 °C. Which color class does it get?
  4. Stations 6 and 8 are light orange, and Station 7 sits between them. What does that spot of blue help a map reader notice about the river?
  5. Why does the map use cool hues, the blues, for readings below the median and warm hues, the oranges, for readings above it?
  6. The darkest blue and the darkest orange sit at the two ends of the palette, and the lightest color sits in the middle. Why does the value get darker toward the ends?
  7. Why did the designer choose blue and orange instead of red and green for the two sides of the palette?
  8. Why is a light gray a better color for the middle class than a bright yellow?
  9. List the five color classes in the order they should appear in the map's legend.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 15 degrees Celsius.
    In order, the readings are 9, 10, 12, 13, 13, 15, 16, 17, 18, 19, 21. With 11 readings, the median is the 6th value, which is 15.
  2. Answer: 12 degrees Celsius.
    The five readings below the median are 9, 10, 12, 13, 13. Their middle value is 12.
  3. Answer: 18 degrees Celsius.
    The five readings above the median are 16, 17, 18, 19, 21. Their middle value is 18.
  4. Answer: 6 degrees Celsius.
    18 - 12 = 6. The middle half of the readings spans 6 degrees.
  5. Answer: 3 stations.
    Stations 1, 2, and 3 read 9, 10, and 12 degrees, so all three are 12 °C or colder.
  6. Answer: 3 stations.
    Stations 9, 10, and 11 read 18, 19, and 21 degrees, so all three are 18 °C or warmer.
  7. Answer: Light blue.
    13 °C falls in the class for 13 °C or 14 °C, which is below the median.
  8. Answer: The cold, spring-fed creek cools the river where it joins.
    A blue station between two orange stations stands out, so the reader sees that something cools the river at that point. Accept any answer that links the cool spot to the creek joining above Station 7.
  9. Answer: Most readers link blue with cold and orange with warm.
    Matching the hues to that meaning lets a reader understand the map before reading the legend. Accept answers that explain the link between the colors and temperature.
  10. Answer: Darker value shows a reading farther from the median.
    The eye is drawn to dark colors, so the stations farthest from typical, the cold water just below the dam and the warm water far downstream, stand out most. Readings near the median stay light and quiet.
  11. Answer: Some readers cannot tell red from green.
    Many people with color vision deficiency confuse red and green. Blue and orange stay easy to tell apart for most of these readers, so the two sides of the palette remain clear.
  12. Answer: Bright yellow looks warm and grabs attention, while gray looks neutral.
    The middle class should not seem to belong to the warm side or draw the eye. A light gray reads as "typical" and lets the blue and orange ends carry the message. Accept answers about yellow reading as warm or as too bright for the middle.
  13. Answer: Dark blue, light blue, light gray, light orange, dark orange.
    The boxes run from coldest to warmest in one steady order, with the gray box in the center. Accept the same order from warmest to coldest if the gray is still in the center.

Differentiation

Support

Give students the 11 readings already sorted on a number line, with the 6th value circled, so they can find the median and then count five values to each side for the quartiles. Provide a blank five-box legend strip with the class labels printed underneath so students only choose and justify the colors for items 9 through 13.

Extension

Ask students to color a simple strip map of the 11 stations with colored pencils using the palette, then make a second strip using a rainbow palette for the same readings. They show both to a classmate, ask which strip makes the cold water below the dam easier to spot, and write a short note to the stream team recommending one palette with reasons.

ELL supports

Pre-teach hue, value, warm, cool, and neutral with a printed color wheel and a gray value scale. Post the terms median and quartile beside a sorted list of numbers with the middle values circled. Allow students to answer items 8 through 13 with short phrases or a labeled sketch of the legend, and provide sentence starters such as "Blue shows ___ because..."