How Sunlight Warms the Earth
Kindergarten students associate the sun with light and warmth. This lesson helps them expand this knowledge by getting their hands dirty! They will fill cups with soil, water and rocks and place them in the sun and shade for a while. By finding out how they can tell where a cup has been stored, they will learn how the sun affects Earth's surface.
In a follow-up lesson, Create Shade to Protect from the Sun, students figure out how to protect a territory from getting too hot in the sun.
- Explain how a material left in the sun for a while is warmer compared to the same material kept in the shade.
- Use the terms "in the sun" and "in the shade" correctly.
NGSS AlignmentThis lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
- K-PS3-1. Make observations to determine the effect of sunlight on Earth's surface.
Science & Engineering Practices
Planning and Carrying Out Investigations. Make observations (firsthand or from media) to collect data that can be used to make comparisons.
Disciplinary Core Ideas
PS3.B: Conservation of Energy and Energy Transfer Sunlight warms Earth's surface.
Cause and Effect. Events have causes that generate observable patterns.
- Plastic cups, 1 per student. Translucent or transparent cups are best, but others are fine too.
- Permanent marker
- Soil, enough to fill one third of the cups. Potting soil or sand work well. The soil should be as dry as possible.
- Pebbles, gravel, or small rocks, enough to fill one third of the cups. Dark colors work best, but lighter colors are fine too.
- Water, enough to fill one third of the cups.
- Towels (3) or paper towels
- A place in the sun to leave half of the cups, preferably indoors (e.g. a window sill). If you place the cups outside, try to find an area protected from wind. If this is not available, a place under an incandescent light source of 60 watt or higher is fine too.
- A place in the shade and away from any heat source (like a radiator) to leave half of the cups, preferably indoors (e.g. a table in your classroom that is not near a window). If you place the cups outside, try to find an area protected from the wind or with equal wind exposure as the area in the sun.
- Student demonstration thermometer (1), like this thermometer.
Background Information for TeachersThis section contains a quick review for teachers of the science and concepts covered in this lesson.
The Sun is the main source of heat and light on Earth. Without it, we could not survive on our planet. The Sun is about 93 million miles (150 million kilometers) away, but because the Sun's surface is so hot (about 10000°F) and bright, we on Earth can still see the light it radiates. The Sun acts like a gigantic bonfire, sending light in all directions, including to Earth.
Figure 1. The Sun illuminates Earth.
The light radiated by the Sun carries energy. When this light reaches a surface, part of it gets absorbed and transformed into heat. That is why places in the sun feel warmer than places in the shade. Your kindergarten students know this from experience. On a cold day, they might prefer to play in the sun; on a hot day, they search for a cool spot in the shade. This lesson helps your students to explore what being in the sun does to the surfaces that cover our Earth. A follow-up lesson, Create Shade to Protect from the Sun, explores creative solutions to protect a surface from the effects of the Sun.
Earth's surface is covered with water (about 70%!), soil, rocks, snow, and ice, and a wealth of man-made materials like concrete. Note that when viewed from space, you could also say that plants (like trees and shrubs) cover the surface of the Earth. For the purposes of this project, we are concerned with the Earth's surface at ground level—so we consider larger plants and shrubs to be things that provide shade to other materials on Earth's surface.
When Earth's surfaces are exposed to the sun, they absorb some of the light and become warmer. In this lesson, your students will feel how soil, rocks, and water feel warmer after being in the sun. If you allow students to feel at different moments, they might notice that this warming effect does not happen instantly, but gradually; this process takes time. They might also notice that some materials warm less or less quickly than others.
Two different materials at the same temperature can feel very different. A metal doorknob will feel colder than a wooden door, even if they are at the same temperature. This occurs because metal is a better conductor of heat, so it absorbs heat from your hand more quickly and thus, feels colder. For this reason, you cannot reliably compare the temperatures of two different materials (e.g. rocks and dirt) by feeling them with your hands. To make a comparison between two different materials, you need to measure their temperatures with a thermometer. Use an infrared thermometer if you want to add temperature measurements to this lesson.