Heat and Evaporation

In the last unit, students learned about matter as they explored Earth’s position in the solar system. In this unit, students discuss how the sun provides light and heat to Earth, powering the water cycle, which in turn influences weather and climate. Students analyze the science phenomena of weather patterns in specific regions during a particular season. This page showcases essential components of this lesson.

Science Background for Teachers:

This science background provides teachers with more in-depth information about the phenomena students explore in this unit.

Temperature is a part of a location’s climate, which is the average weather of a location over 30 years or more. Weather is the condition of the atmosphere (temperature, humidity, wind speed, air pressure, and precipitation) at a particular place and time. Weather changes hour-to-hour, while climate changes over very long periods of time.

All weather and climate conditions around the planet begin with the sun. The position of Earth relative to the sun is one of the most important factors influencing weather and climate because it causes uneven heating of the planet. It is widely believed that the equator is warmer than other parts of the planet because it is closest to the sun. This is not true. It is actually Earth’s spherical shape and its 23.5-degree tilt on its axis that causes climate differences.

At sea level, temperatures are highest near the equator and decrease as latitude increases toward the North and South poles. This is because at the equator, the sun’s rays are most direct and concentrated. Moving north or south of the equator, the sun’s rays are spread over a larger area, so each square meter of Earth’s surface is receiving less solar energy.

As a result of how the sun’s rays hit Earth, the planet is divided into three main climate zones: a tropical zone, temperate zones, and polar zones. These zones are determined by average temperature and average rainfall. When monarch butterflies head south, they travel from a temperate climate to a tropical one.

The tropical zone is around the equator. It has the warmest temperatures and gets the most rain. In the tropical zone, the average temperature in the coldest month is 18 degrees Celsius (64 degrees Fahrenheit). This is warmer than the average temperature of the warmest month in the polar zone.

The temperate zones are located between the equator and the North and South poles. Temperatures in this zone are moderate, and rain falls year-round.

The North and South poles have polar climates, where the warmest months average less than 10 degrees Celsius (50 degrees Fahrenheit). This is lower than the average temperature of the coldest months in the tropical zones.

Supports Grade 3

Science Lesson: Exploring 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.

Science Big Ideas

  • 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.

Sample Unit CTA-2
Discover Complete Hands-on Screens-off Core Science Curriculum for K-8 Classrooms

Prepared hands-on materials, full year grade-specific curriculum, and personalized live professional development designed to support mastery of current state science standards.

Science Essential Questions

  • 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?

Common Science Misconceptions

Misconception: Water that evaporates has disappeared.

Fact: Matter never disappears. Evaporation refers to the process of liquid water turning into a gas. It is still present even though we cannot see it.

Misconception: Earth is closer to the sun in the summer, and that is why it is hotter.

Fact: Seasons occur because Earth is tilted on its axis. Locations experiencing summer are tilted toward the sun.

Science Vocabulary

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

Lexile(R) Certified Non-Fiction Science Reading (Excerpt)

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.


Hands-on Science Activity

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.

Science Assessments

KnowAtom incorporates formative and summative assessments designed to make students thinking visible for deeper student-centered learning.

  • Vocabulary Check
  • Lab Checkpoints
  • Concept Check Assessment 
  • Concept Map Assessment 
  • And More...

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Science Standards

See How KnowAtom Aligns to NGSS Science Standards

Discover hands-on screens-off core science curriculum for student centered K-8 classrooms. KnowAtom supports classrooms with all hands-on materials, curriculum, and professional development to support mastery of the standards.

Download the Alignment to NGSS

Standards citation: NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.