Students will investigate density, polarity, and gas production through a Valentine’s Day–themed lava lamp investigation. Using oil, water, food coloring in Valentine colors, and heart-themed effervescent tablets, students explore how chemical reactions can make liquids move in surprising ways—perfect for connecting science to a holiday they recognize.

As students add different amounts of the tablet, they observe how carbon dioxide gas bubbles temporarily change the density of the colored water, causing it to rise and fall through the oil layer like floating Valentine “hearts.” Students record observations, compare trials, and identify patterns between tablet amount, gas production, and fluid motion.

Note: This Investigation is similar to my 'Homemade Lava Lamp STEM Investigation - Density & Gas Production' but with a Valentine's Day twist.

Learning Targets

• Plan and carry out a controlled investigation with repeated trials
• Observe how liquids of different densities interact
• Investigate how gas production affects motion in fluids
• Identify cause-and-effect relationships in physical systems
• Construct a CER explaining fluid motion using density and gas production concepts

What’s Included

Teacher Guide

Setup tips, safety notes, and background explanations of density, polarity, and gas-producing reactions. Includes guidance for standardizing oil-to-water ratios, tablet amounts, timing, and observation procedures to ensure fair comparisons.

Student Packet

Hypothesis prompt, variables chart, step-by-step setup instructions, structured data tables, observation recording pages, analysis questions, and a guided CER response.

Analysis & Answer Key

Expected patterns (more tablet → more gas → increased motion), sample data, detailed explanations, common error sources, and a full model CER grounded in density and gas production.

Rubric

Assesses understanding at every stage of the lab, including background knowledge, experimental design, data collection, analysis, CER writing, collaboration, and safety.

What Students Will Learn

• How density differences affect whether substances float or sink
• Why oil and water do not mix
• How gas production changes density and causes motion
• How to design and conduct a fair scientific investigation
• How to analyze patterns and explain results using evidence
• How to use Claim–Evidence–Reasoning (CER) to support scientific explanations

Why Teachers Love It:

• It incorporates some Valentine's Day fun into the science classroom
• Low-prep & inexpensive — common classroom materials only
• Highly visual and engaging — students love watching the lava lamp motion
• Builds core lab skills: variables, controls, observation, consistency
• Strong connection between physical science and chemistry concepts
• Includes structured CER writing, not just “fun science”
• Perfect for STEM days, matter units, review lessons, or sub plans

➡️ You can get this STEM as well as all my other ones in this series inside my STEM Investigations Growing Bundle. As more labs are added, the price will increase. CLICK HERE to have a look

Best For

Physical Science (density, mixtures, reactions), chemistry foundations, lab skills, CER writing, STEM challenges, or sub-friendly hands-on lessons.

Materials Needed

Clear container (plastic bottle or cup), vegetable oil, water, food coloring, effervescent tablets (Alka-Seltzer or similar), measuring cups/spoons, timer, paper towels, student packet (included).

Estimated Timing

1 class period for setup → testing → data collection → CER writing

Add 10–20 minutes for discussion questions and improvement proposals

➡️ You can get this activity inside my STEM Investigations Growing Bundle.

I also have the following STEM Labs in My Store:

• Blow Cup Challenge STEM Lab
• Paper Table STEM Lab
• Pendulum STEM Lab
• Parachute STEM Lab
• Catapult STEM Lab
• Paper Airplane - Angle of Attack STEM Lab
• Bottle Flip STEM Lab
• Paper Helicopter STEM Lab
• Yeast Balloon STEM Lab
• Balloon Lift Design STEM Lab
• Candy Combustion Calorimetry STEM Lab
• Marble Ramp: Height vs Average Speed STEM Lab
• Clean Water Filtration STEM Lab
• Beetle Genetics STEM Lab
• Adaptations by Design - Extreme Environments STEM Lab
• Newton's 1st Law of Motion STEM Lab - Penny and Index Card - Inertia Test
• Newton's 2nd Law of Motion STEM Lab - Balloon Rocket
• Newton's 3rd Law of Motion STEM Investigation - Thrust vs Nozzle Size
• Electromagnet - Coil Turns vs Magnetic Strength
• Oobleck: Force vs Flow — Non-Newtonian Fluids
• Homemade Lava Lamp - Density & Gas Production - STEM Investigation

NGSS alignment

MS-PS1-2, MS-PS2-2 (properties of matter, forces & interactions)

Practices: Planning & Carrying Out Investigations; Analyzing Data; Constructing Explanations; Argument from Evidence

Assessment

Use the included rubric to score experimental design, procedure consistency, observation quality, scientific reasoning, CER strength, collaboration, and safety.