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Human Energy Systems | Lesson 1 - Pretest and Expressing Ideas

Lesson 1: Pretest and Expressing Ideas

Students take the unit pretest, practice how and why scientists construct graphs to represent data, and construct a graph of arctic sea ice extent from 1979-2015 and identify a trend in the data: arctic sea ice is declining.

Guiding Question

What is happening to arctic sea ice?

Activities in this Lesson

  • Activity 1.1: Human Energy Systems Unit Pretest (20 min)
  • Activity 1.2: Expressing Ideas about Arctic Sea Ice (20 min)
  • Activity 1.3: Graphing Arctic Sea Ice (45 min)
  • Activity 1.4: Drawing a Trend Line (20 min)
  • Activity 1.5: Finding a Trend in Arctic Sea Ice (40 min)


  • Distinguish between short-term variability and long-term trends in large-scale data sets.
  • Explain how data are sampled and represented in different representations of large-scale data sets (e.g., graphs, maps, videos).

NGSS Performance Expectations

Middle School

This lesson does not feature a mastery of any of the NGSS performance expectations, but provides students with foundational practices and knowledge needed to master all of the performance expectations in the rest of the unit.

Background Information

Activity 1 includes the pretest for this unit. The discussion in this activity (a) helps students to anticipate and begin thinking about the questions that they will answer in this lesson and (b) helps you as a teacher see how your students reason about matter, energy and the carbon-transforming processes of photosynthesis, cellular respiration, and global carbon cycling.

Activity 2 establishes an important question: why is arctic sea ice melting? Although students do not gather the evidence they need to answer that question in this lesson, in this activity they are given an opportunity to share their initial ideas about why this phenomenon might be happening.

Activity 3 gives students an opportunity to practice interpreting data in the arctic sea ice graph, which is one of many data sets they will use throughout the Human Energy Systems Unit. Students retrieve data from a publically available data set about arctic sea ice. They use the data to construct a graph. When they first construct the graph, it is difficult to see a trend due to the noisy nature of the data. They also discuss how different representations of data allow for different interpretation and knowledge.

In Activity 4, students use samples of messy data sets (similar to arctic sea ice) to find a “signal in the noise.” The students develop different strategies for finding a trend line in noisy data. Finding a trend is a key practice in analysis of scientific data sets. Finding global trends in merged data sets, for example, is how scientists have learned that climate change is taking place as a result of human activity. This activity helps students develop a critical eye when analyzing data that ideally will help them distinguish a pattern in what appears to be messy data.

In Activity 5, students then return to their graphs of arctic sea ice and use the same strategies from the previous activity to find a trend in their arctic sea ice data. They discover that arctic sea ice extent is decreasing over time. However, at the end of this lesson they only have evidence to show that the ice is decreasing, but not why. These questions will be answered later in the unit when the students discuss the greenhouse effect and CO2 emissions.