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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 (40 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 publicly 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.

Unit Map

Unit Map for Lesson 1

Talk and Writing

At this stage in the unit, the students will be Expressing Ideas. The table below shows specific talk and writing goals for this phase of the unit.

Talk and Writing Goals for Expressing Ideas Phase

Teacher Talk Strategies that Support this Goal

Curriculum Components that Support this Goal

Treat this as brainstorming and elicitation.

Remember, there are no “right” answers at this point. We want to hear all ideas.

Unit Pretest

My Students’ Answers

Listen for ideas about what is happening to matter and energy at different scales.

Where did the energy come from?

Where does the matter go next?

Are you talking about matter or energy?

What about the atomic-molecular scale?

What about the cellular scale?

Unit Pretest

Expressing Ideas Process Tool

Listen for a wide range of student ideas. Press for more complete ideas.

Who can add to that?

What do you mean by _____? Say more.

So I think you said _____. Is that right?


Have students compare, contrast, and document their ideas.

Who has a different idea?

How are those ideas similar/different?

Who can rephrase ________’s idea?

Let’s record our ideas so we can come back to them and see how our ideas change.

Sticky notes on the class poster

Activity 1.2 Presentation

Encourage students to provide evidence for their ideas.

How do you know that?

What have you seen in the world that makes you think that?

Sticky notes on the class poster.