Heat and Evaporation

In this first lesson of the unit, students observe how heat influences evaporation, analyzing how heat from the sun powers the water cycle and causes water to move around Earth. They discuss how the sun’s rays are more concentrated near Earth’s equator and less concentrated the farther north and south you go, which causes different regions to receive varying amounts of heat. As water moves around the planet, it transfers heat.

• The sun provides light and heat to Earth.
• Different parts of Earth have different climates because of the amount of direct sunlight they receive. Climate is the average weather over a span of 30 years.
• The sun’s rays don’t hit Earth evenly. Some places on Earth receive more direct sunlight, which makes them warmer.
• Almost 75 percent of the planet is covered in water, and as the sun heats Earth, it causes water to move around the planet.
• Because of Earth’s place in the solar system and resulting temperature, it is the only known planet to have water in all three states: solid, liquid, and gas.
• Water moves throughout Earth because of the different amounts of heat on the planet.

• How does the sun affect Earth?
• Why are regions close to the equator warmer than other places on Earth?
• How does the amount of sunlight an area receives relate to its average climate?
• Where are some places on Earth where water is found?
• How does heat cause water molecules to change their motion?
• What is the primary factor that causes water to cycle throughout Earth?
• How do we know that evaporated water hasn’t just disappeared?
• How does the state of water change when it evaporates?

Air Pressure : a measure of the force of air’s weight on Earth’s surface; measured with a barometer

Climate : the average weather over a span of 30 years

Evaporation : the process of liquid water changing into water vapor, its gas state

Precipitation : the process of water falling back to Earth in the form of rain, snow, sleet, or hail

Proportion : the relationship between things, as to size, quantity, or number

Season : a time of year that has specific weather patterns and amounts of daylight

Temperature : a measure of heat; measured with a thermometer

Water Cycle : the circulation of water from a collection to the atmosphere and back to Earth in

Four Steps: evaporation, condensation, precipitation, collection

Weather : the conditions of the atmosphere (temperature, humidity, wind speed, air pressure, and precipitation) in a particular place at a particular time

Wind Speed : a measure of how fast wind is moving; measured with an anemometer

Traveling Butterflies

Every fall, millions of butterflies begin a long journey. They start in Canada and the northern United States. They end in Mexico or southern California. This journey can take up to 2 months.

These butterflies have wings with bright orange and black patterns. They are called monarch butterflies. They fly south every year because they cannot survive cold winters. Their ideal temperature is between 0 and 15 degrees Celsius (32 and 59 degrees Fahrenheit). Temperature is a measure of heat.

All of Earth is warmed by heat from the sun. Earth’s land, oceans, and atmosphere absorb the sun’s energy. This makes them warmer. Different parts of the world have different temperatures because of how they are heated by the sun.

Weather and Climate

Monarch butterflies spend the winter in a warm climate. Climate is the average weather over a span of 30 years. Weather refers to the conditions of the atmosphere in a particular place at a particular time. For example, rain is a kind of weather. Wind is another kind of weather. Weather changes hour-to- hour. Climate changes over very long periods of time.

Earth is divided into three main climate zones. These zones are tropical, temperate, and polar. They are determined by temperature and rainfall.

Temperatures in the temperate zone are not too high and not too low. Rain falls year-round in this zone. The tropical zone has the warmest temperatures. It gets the most rain. The polar zones are near the North and South poles. They have the coldest temperatures. Temperatures are almost always below freezing.

When monarch butterflies fly south, they travel from a temperate zone to a tropical zone.

 

In this lesson, students carry out an experiment to see if water evaporates faster in warm locations compared to cool locations. Students create a scientific diagram of their experiment- in-progress and record observational data on the initial and final appearance of the paper towel (wet or dry) for each trial. Then, students use the data to construct an explanation about whether their hypothesis about the rate of evaporation in cool versus warm locations was true, false, or inconclusive.