Investigate how sunlight warms land and water

Learning goal (for the adult): Use observations to explain how exposure to sunlight can change the warming of land and water. The sun is Earth's principal energy source. Sunlight warms surfaces; warmed surfaces can also warm nearby air. Shade can reduce direct sunlight, but a shaded place is not automatically cold. Air temperature, wind, starting temperature and time also matter.

Begin with an everyday observation: a sunny part of a playground may feel warmer than a shaded part. That observation raises a question, but it does not yet explain every difference. The sunny area might be dark pavement while the shaded area is grass. To investigate sunlight exposure, compare similar materials under carefully described conditions rather than changing everything at once.

The illustration shows two identical shallow containers with equal amounts of water. Both start at the same measured temperature. One receives direct sunlight and one is shaded. The labels identify conditions, not results. A picture of sunshine does not prove how many degrees a sample warmed. Only readings collected during the investigation can supply that evidence.

An adult places the containers securely and uses an appropriate non-glass classroom thermometer. Children observe without looking directly at the sun or touching surfaces that might be hot. Read the water temperature before exposure and again after the same amount of time. The adult can read the numbers aloud. Draw two columns and keep the readings attached to the correct container. A larger ending number describes warmer water only when both readings use the same temperature scale.

Repeat with two matching trays of the same soil if suitable materials are available. Keep the amounts, containers, starting conditions and observation times as similar as practical. Water and soil need not warm at the same rate. Comparing sunlight and shade within each material answers a clearer question than comparing a tiny water sample with a large, different soil sample.

Sunlight does not act like a substance poured into a cup. It transfers energy that can warm material. We do not need to see energy itself to observe a temperature change. When sunlight exposure decreases, warming from sunlight can decrease; whether the material actually cools also depends on its surroundings. Use careful language such as “this sample warmed more during our trial” instead of “sunny water is always hotter.”

Sunlight warms air too, mostly by first warming the ground and water, which then warm the air just above them. That is one reason the air over a sunny patch of ground can feel warmer than the air in deep shade. Measuring air temperature fairly is harder than measuring water: a thermometer left in direct sunlight is warmed by the sunlight itself, so its reading is not just the air’s temperature. For this grade, let an adult read a thermometer that is kept shaded from direct sun in each place. Exposure can also change in the other direction. When a cloud covers the sun for a long time, or a building’s shadow moves across a sunny spot, the land, water and air there receive less sunlight and can cool. The amount of exposure to sunlight affects how much a place warms or cools.

Read aloud to the children: The sun gives us light. Sunlight can make things warmer. It warms the ground. It warms water. It warms the air too. A spot in the sun often gets warmer than a spot in the shade. When a cloud or a shadow covers a sunny spot, that spot gets less sunlight. Then it can cool down. We use a thermometer to find out. A grown-up reads it with us. Never look right at the sun.

Worked example 1: Read invented practice measurements. Both water samples begin at 20 degrees Celsius. After the same interval, the sunny sample reads 24 and the shaded sample reads 21. The sunny sample warmed by four degrees and the shaded sample by one. These invented numbers illustrate how to compare a record; they are not promised classroom results. First graders can compare the starting and ending numbers with adult help.

Worked example 2: Identify an unfair comparison. A dark metal tray of soil is placed in sunlight while a large white bowl of water is placed in shade. Their different temperatures cannot be attributed only to sunlight exposure. Material, container and amount also changed. Redesign with matching containers and the same material.

Worked example 3: Explain an unexpected result. Clouds arrive and both samples end at nearly the same temperature. Record that result and note the changed conditions. Do not replace the readings with the expected answer. Another trial with clearer exposure differences may help investigate the question.

Guided investigation: Ask partners to point to the sunlight and shade labels, name what should stay alike, and predict which sample might warm more. Collect actual readings with an adult. Compare the results with the prediction and name one condition that might have affected the comparison.

Independent tasks: Draw the two-container setup, label its exposure conditions, interpret the invented readings above, and explain why a result must come from observations rather than the illustration. Describe how sunlight can warm land or water and how warmed surfaces can affect nearby air.

Feedback: If a learner equates shade with freezing, compare actual shaded conditions on a warm day. If the learner counts drawn sunlight rays as units of temperature, explain that the rays identify sunlight exposure, not a measurement. Credit a conclusion that names the sample and the evidence, even if the real trial does not match a prediction.