Grade: Grade 6 Subject: Science Unit: Earth & Space Lesson: 3 of 6 ACT: Science

Investigation Lab: Earth and Space Models

Learn

In this investigation lab, you will apply the scientific method to explore Earth's structure and space phenomena through hands-on modeling activities.

Why Scientists Use Models

Scientists cannot directly observe many Earth and space phenomena. The Earth's core is over 2,900 km below the surface, and distant planets are millions of kilometers away. Scientific models help us understand things we cannot directly see or measure.

Types of Scientific Models

  • Physical models: 3D representations like globes, model volcanoes, or cross-sections of Earth
  • Conceptual models: Diagrams and illustrations that explain processes
  • Mathematical models: Equations and formulas that describe phenomena
  • Computer models: Simulations that show changes over time

The Scientific Method in Earth Science

  1. Ask a question: What do you want to know about Earth or space?
  2. Research: Gather existing information about your topic
  3. Form a hypothesis: Make a testable prediction
  4. Design an experiment: Plan how to test your hypothesis
  5. Collect data: Record observations and measurements
  6. Analyze results: Look for patterns in your data
  7. Draw conclusions: Determine if your hypothesis was supported

Investigation Focus: Modeling Earth's Layers

Today's investigation focuses on creating and analyzing a model of Earth's internal structure. You will explore how density affects the arrangement of Earth's layers.

Key Concept: Density Stratification

Earth's layers are arranged by density. The densest materials (iron and nickel) sink to the core, while less dense materials (silicate rocks) form the mantle and crust. This process occurred early in Earth's history when the planet was still molten.

Examples

Example 1: Density Column Model

Question: How do different densities create layers?

Materials: Clear container, honey, corn syrup, dish soap, water, vegetable oil, rubbing alcohol

Procedure:

  1. Slowly pour each liquid into the container, starting with honey
  2. Add each subsequent liquid by pouring along the side of the container
  3. Observe how the liquids form distinct layers

Connection to Earth: Just like these liquids, Earth's layers separated by density. The inner core (densest) is at the bottom, followed by the outer core, mantle, and crust (least dense).

Example 2: Hard-Boiled Egg Earth Model

Observation: A hard-boiled egg can represent Earth's layers.

  • Shell = Crust (thin, brittle outer layer)
  • Egg white = Mantle (thick, semi-solid layer)
  • Yolk = Core (dense center)

Limitation: This model doesn't show that the outer core is liquid or that the mantle can flow slowly over time.

Example 3: Analyzing Seismic Wave Data

Scientists learn about Earth's interior by studying how seismic waves travel through the planet.

Wave Type Travels Through What It Reveals
P-waves (Primary) Solids and liquids Speed changes indicate layer boundaries
S-waves (Secondary) Solids only Blocked by liquid outer core

Practice

Complete the following practice problems to reinforce your understanding of scientific investigation and Earth modeling.

1. A scientist wants to study how convection currents in Earth's mantle cause tectonic plate movement. Which type of model would be MOST useful?

  1. A physical clay model of Earth's layers
  2. A mathematical equation for plate speed
  3. A computer simulation showing heat flow over time
  4. A conceptual diagram of plate boundaries

2. In a density column experiment, a student adds water (density 1.0 g/mL), vegetable oil (0.92 g/mL), and honey (1.4 g/mL). From bottom to top, the correct order of layers should be:

  1. Oil, water, honey
  2. Honey, water, oil
  3. Water, honey, oil
  4. Honey, oil, water

3. Why do S-waves NOT travel through Earth's outer core?

  1. The outer core is too hot
  2. S-waves can only travel through liquids
  3. S-waves cannot travel through liquids
  4. The outer core reflects all seismic waves

4. A model of Earth shows the crust as 5 cm thick and the mantle as 10 cm thick. In reality, the crust averages 35 km and the mantle is about 2,900 km. What is a limitation of this model?

  1. The model is too small
  2. The model shows incorrect relative thicknesses
  3. The model doesn't show temperature
  4. The model uses the wrong materials

5. Which step of the scientific method involves making a prediction that can be tested?

  1. Asking a question
  2. Forming a hypothesis
  3. Collecting data
  4. Drawing conclusions

6. Scientists discovered that P-waves slow down when they enter the mantle from the crust. What can they conclude?

  1. The mantle is made of the same material as the crust
  2. The mantle has different properties than the crust
  3. P-waves cannot travel through the mantle
  4. The crust is denser than the mantle

7. A student hypothesizes: "If I drop objects of different densities into water, then denser objects will sink faster." What is the independent variable in this experiment?

  1. The speed of sinking
  2. The density of the objects
  3. The depth of the water
  4. The time to reach the bottom

8. Which of the following is NOT a valid reason for using models in Earth science?

  1. The actual phenomena are too large to observe directly
  2. Models can predict future events
  3. Models are always 100% accurate representations
  4. Direct observation would be dangerous or impossible

9. During an investigation, a student's results do not support their hypothesis. What should they do next?

  1. Change the data to match the hypothesis
  2. Conclude that the experiment failed
  3. Analyze why the results differed and possibly revise the hypothesis
  4. Repeat the experiment until the hypothesis is supported

10. A physical model of Earth's layers uses different colored clay. Which feature of Earth's interior is MOST difficult to represent in this type of model?

  1. The different layer thicknesses
  2. The spherical shape of Earth
  3. The extreme temperatures and pressures
  4. The different compositions of each layer

Check Your Understanding

Reflection Question 1: You are designing a model to show how seismic waves travel through Earth. What materials and methods would you use? What limitations would your model have?

Reflection Question 2: Explain why scientists cannot directly observe Earth's core but are still confident about its composition and structure.

Practice Problem Answers

1. C | 2. B | 3. C | 4. B | 5. B | 6. B | 7. B | 8. C | 9. C | 10. C

Next Steps

  • Review the scientific method and practice identifying variables in experiments
  • Think about what other Earth and space phenomena could be modeled
  • Continue to the next lesson on Data and Graphs to learn how to analyze your investigation results