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Cold Air is Dense


We wish to set up a learning situation in which students will discover, through the examination and manipulation of real data from a natural environment, that:

These insights are absolutely fundamental to understanding virtually everything about weather and climate. Until a student has his or her mind firmly around these two concepts, he or she is not ready to understand how storms work, not ready to understand why the prevailing winds blow the way they do, not ready to understand why deserts occur where they do.

Although these two concepts are fundamental underpinnings of virtually every physical process in the atmosphere, they are not intuitively obvious--in fact, they are counter-intuitive. The student looks around at the air skeptically-- if there are so many molecules in that air, why can't we see them? If air has weight, why doesn't it register on a scale? On hot summer nights, the air feels oppressive, heavy--don't tell me that hot August air is low density "Air has mass", "air has density", and "cold air is dense" are the kinds of statements that students tend to memorize and parrot back, without actually altering their world-view, because these statements don't fit with their day-to-day experience of real-life air.

Because an understanding of the relationship between density and temperature of air is fundamental to so many natural processes, yet is counter-intuitive, it is a good investment of student and instructor time to construct this understanding upwards from a solid basis in the observation of real data.

Insights/Curriculum Highlights:

Thinking Skills / Pedagogical Highlights:


1. Introductory Hands-on Investigation: Make a Barometer

2. Video : Torricelli's discovery of air pressure

3: Reproduce Torricelli's experiment in a tall building

4. Data-based investigation: barometric pressure from BRF

5. Data-based investigation: qualitative relationship between density & temperature of air

6. Data-based investigation: quantitative relationship between density & temperature of air

Created by Kim Kastens, Lamont-Doherty Earth Observatory (
May be freely used for educational purposes provided appropriate credit is given.

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