Halloween Science – Decomposing Pumpkin Jack – o – Lantern

Decomposing Pumpkin Jack turns a carved jack-o’-lantern into a memorable Halloween science experiment for K–2! Students predict what will happen to Pumpkin Jack, observe the pumpkin as it decomposes over time, record changes, compare before and after, and draw conclusions using real science observations.

This Halloween science experiment and pumpkin science activity gives students an engaging way to observe decomposition firsthand while practicing prediction, observation, data recording, comparison, descriptive vocabulary, and beginning scientific reasoning. The included teacher guide, experiment sign, and student recording pages make the activity easy to set up and continue over several days or weeks.

---

🍂 WANT MORE PUMPKIN LEARNING? UPGRADE TO THE COMPLETE BUNDLE!

This resource is included in my All About Pumpkins Activities Bundle, packed with hands-on pumpkin science, STEM, life cycle activities, math, reading, writing, crafts, map skills, pumpkin patch activities, and more for K–2. Use the activities throughout the month of October for weeks of connected pumpkin learning — and save when you purchase the complete collection!

👉 CLICK HERE TO GET THE COMPLETE PUMPKIN ACTIVITIES BUNDLE + SAVE!

---

What’s Included

• Decomposing Pumpkin Jack classroom experiment
• “Decomposing Jack — Please Do Not Touch!” display sign
• Teacher experiment guide
• Materials and setup directions
• Experiment question
• Hypothesis section
• Student observation recording page
• Multiple observation-day spaces
• Before-and-after recording activity
• Changes-in-properties checklist
• Conclusion and share-your-results section
• Student drawing and writing response
• K–2 classroom science activity

Set Up the Decomposing Pumpkin Experiment

Start with a carved class jack-o’-lantern and place it inside a clear container for students to observe.

Students investigate the question:

How long will our Jack-o’-lantern last?

Students make predictions before the pumpkin begins changing and then return to the experiment over time to observe what happens.

The included display sign identifies the experiment as an ongoing classroom investigation and reminds students not to disturb Pumpkin Jack while they observe the decomposition process.

Predict + Observe

Before decomposition begins, students think about what they expect to happen to Pumpkin Jack.

As the experiment continues, students observe the real jack-o’-lantern and record visible changes.

Students can:

• Make a prediction
• Observe Pumpkin Jack over time
• Draw what they see
• Record changes
• Compare observations from different days
• Discuss what is happening
• Use evidence from the experiment to explain their thinking

Watch Pumpkin Jack Change Over Time

Students observe how Pumpkin Jack changes as decomposition progresses.

They can notice and discuss changes in:

• Color
• Shape
• Texture
• Smell
• Mold
• Overall appearance

This gives young learners an authentic reason to use descriptive science vocabulary and compare observations from different points in time.

Compare Before + After

Students draw what Pumpkin Jack looked like before the experiment and what it looks like after decomposition has occurred.

They then identify the changes they observed.

Students compare characteristics such as:

• Color: same, darker, spotted
• Shape: same, smaller, squishy
• Texture: smooth, soft, mushy
• Smell: no smell, a little smell, a strong smell
• Mold: none, a little, a lot

This structured format helps K–2 students make meaningful scientific comparisons without requiring lengthy writing.

Draw + Record

Students use the observation page to document Pumpkin Jack throughout the experiment.

They can:

• Draw Pumpkin Jack on different observation days
• Track visible changes
• Compare earlier and later observations
• Use pictures and words to record evidence
• Discuss how the pumpkin changes over time

Conclude + Share

At the end of the experiment, students draw and write about what happened to Pumpkin Jack.

Students experience a simple version of the scientific process:

• Ask a question
• Make a prediction
• Observe
• Record
• Compare
• Draw a conclusion
• Share results

Perfect For

• Halloween science
• Halloween science experiments
• Pumpkin science
• Pumpkin science experiments
• Pumpkin decomposition
• Jack-o’-lantern science
• Fall science experiments
• October science activities
• Science centers
• Whole-group science
• Observation lessons
• Seasonal STEM
• Scientific method practice
• Before-and-after comparisons

Skills Practiced

Science

• Observation
• Prediction
• Decomposition
• Changes over time
• Comparing physical characteristics
• Drawing conclusions

Scientific Inquiry

• Asking questions
• Making a hypothesis
• Observing
• Recording evidence
• Comparing results
• Communicating conclusions

Literacy

• Descriptive vocabulary
• Drawing to communicate information
• Short written responses
• Speaking and listening
• Explaining observations

Teacher-Friendly Setup

This resource includes both teacher support and student recording materials, making it easy to turn a classroom jack-o’-lantern into an ongoing science investigation.

Use the experiment as a short daily or weekly observation routine. Students can return to Pumpkin Jack throughout the experiment and watch how the same pumpkin changes over time.

Grades: K–2

Subjects: Science • STEM • Writing

Themes: Halloween • Pumpkins • Fall • Decomposition • October

Decomposing Pumpkin Jack gives students a hands-on Halloween science experiment they can actually watch change over time while practicing prediction, observation, recording, comparison, and scientific thinking.