Sugar crystals in jars: a safe and fun experiment

🎯 General objective.

Understand the process of crystallization creating sucrose crystals by means of a supersaturated solution and analyze how variables such as temperature or sugar purity affect growth.

💪 Personal objective

Plan, execute and communicate a clear experiment with well-organized data and appealing visuals to impress judges and audiences at the science fair.

🌍 Theoretical introduction

When you dissolve a lot of sugar in hot water, you get a supersaturated solution. As the water cools and some of it evaporates, the sugar molecules are rearranged creating crystals 🧊.

More temperature ⇒ more solubility.
Slow cooling ⇒ crystals larger.
Impurities or vibrations ⇒ crystals smaller.

Did you know? Salt (NaCl) forms cubes, while sugar (sucrose) forms elongated prisms.

🔬 Scientific method: your plan of attack.

Observation: Crystals appear in concentrated solutions.
Question: How does the initial temperature influence the size of the crystals?
Hypothesis: The higher the initial temperature, the larger the crystals will be.
Design: Maintain constant bottles and volume; change only the initial temperature.
Data: Measure every 24 h the length of the crystal in mm.
Analysis: Size vs. temperature graph.

Pro Tip: Take daily photos to document progress on your final poster.

🧩 Experiment setup

Use a glass jar to suspend a stick from a clamp, keeping it from touching the walls.


Side view of the assembly:
┌───────────────────────────┐
│ Clamp / Bracket │
│ ──────────────── │
│ │ │ │
│ | │
│ Crystals │
│ | │
│ Solution │
│ | │
│ Bottle │
└───────────────────────────┘

Security: Hot liquid can cause burns. Handle with the help of an adult.

🛠️ Bill of Materials

Material	Economic	Standard	Professional
Sugar	Common white	Refined white	Food grade
Water	Filtered faucet	Bottled	Distilled
Container	Resistant glass	Glass flask	Borosilicate flask

🧭 Step-by-step guide

Nucleation: Moisten the stick and dip it in sugar. Let it dry.
Heating: Heats water without bringing it to a violent boiling point.
Saturation: Add sugar little by little (approx. 3 parts sugar to 1 part water).
Dumping: Pour the solution into the bottle and suspend the stick.
Wait: Let stand for 3 to 7 days in a place without vibrations.