Science activity
Crystal Growing Lab
Grow sparkly crystals from sugar water! Dip a string into sweet water and watch crystals appear over a few days. It is like making candy and doing science at the same time!
Materials and setup
- sugar
- salt
- Epsom salt
- hot water
- clear jars
- string
- pencils
- magnifying glass
- paper
- markers
How this changes by age
Pre-K (ages 3–4)
Grow sparkly crystals from sugar water! Dip a string into sweet water and watch crystals appear over a few days. It is like making candy and doing science at the same time!
Steps
- With a parent, heat 1 cup of water and dissolve 3 cups of sugar, stirring constantly until clear.
- Pour the sugar water into a clear jar.
- Tie a string to a pencil, wet the string and roll it in sugar. Lay the pencil across the jar so the string hangs in the solution.
- Put the jar in a safe spot and wait! Check every day and draw what you see.
- After 5-7 days, pull out your crystal-covered string. 'The sugar came back out of the water and made crystals!'
- Tell a grown-up one thing that surprised you.
Learning objectives
- Observe that crystals grow from a sugar solution over time
- Practice patience and daily observation of slow changes
- Understand that dissolved substances can come back out of solution as solid crystals
Kindergarten (ages 5–6)
Grow two types of crystals — sugar and salt — and compare how they look different. Learn that crystals form when dissolved substances come out of water.
Steps
- Grow sugar crystals: dissolve as much sugar as possible in hot water (parent heats). Pour into a jar with a string hanging from a pencil. Seed the string with sugar.
- Grow salt crystals: dissolve as much salt as possible in hot water. Pour into a separate jar with a string hanging from a pencil.
- Place both jars in a safe, undisturbed spot.
- Observe both jars every day for a week. Draw what you see. Which crystals appear first?
- After a week, compare the crystals with a magnifying glass: sugar crystals are large and chunky, salt crystals are small and cubic.
- Talk about why: 'When water evaporates slowly, the dissolved sugar and salt come back together as crystals.'
- Tell a grown-up one thing that surprised you.
Learning objectives
- Grow crystals from two different supersaturated solutions
- Compare crystal shapes formed by different substances
- Understand that crystal formation occurs when water evaporates from a solution
Early elementary (ages 6–8)
Conduct a crystal growing investigation: test which substances make the best crystals, explore how temperature and evaporation rate affect crystal size, and learn about crystal structure at the molecular level.
Steps
- Research: crystals form when a supersaturated solution cools or evaporates. Molecules arrange themselves in repeating patterns — the crystal shape reflects the molecular structure.
- Grow crystals from 3 different substances: sugar, salt, and Epsom salt (magnesium sulfate). For each, dissolve the maximum amount in hot water and set up a jar with a string.
- Test evaporation rate and crystal size: for one substance, set up 3 jars — one in a warm spot (fast evaporation), one at room temperature, one in the fridge (slow). Which produces the largest individual crystals?
- Observe daily with a magnifying glass. Draw each crystal type and describe its shape (sugar = monoclinic, salt = cubic, Epsom = needle-like).
- Research crystal shapes: why are salt crystals always cubes? Because sodium and chloride atoms arrange in a cubic lattice. Draw the molecular arrangement for salt.
- Write a lab report: compare your three crystal types, analyze the effect of evaporation rate on crystal size, and explain crystal structure at the molecular level.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Grow and compare crystals from multiple supersaturated solutions
- Investigate how evaporation rate affects crystal size and quality
- Explain that crystal shape reflects the molecular arrangement of the substance
Upper elementary (ages 8–10)
Conduct advanced crystallography: grow large single crystals using seed crystal technique, study crystal systems, explore real-world applications of crystallography, and analyze crystal geometry mathematically.
Steps
- Grow a large single crystal using the seed technique: (1) Make a supersaturated alum solution (available at grocery stores in the spice section). (2) Let small seed crystals form. (3) Select the best-shaped seed and suspend it in a fresh supersaturated solution. (4) Let it grow for 1-2 weeks undisturbed.
- Research the 7 crystal systems: cubic, tetragonal, orthorhombic, hexagonal, trigonal, monoclinic, and triclinic. Identify which system each of your crystals belongs to.
- Measure your crystals: use a ruler and protractor to measure edge lengths and angles. Verify that the geometry matches the expected crystal system (e.g., salt = cubic = 90-degree angles, equal edges).
- Research how crystals are used in technology: quartz in watches (piezoelectric effect), silicon crystals in computer chips, diamonds in cutting tools, liquid crystals in screens.
- Investigate crystal defects: what happens when crystals grow too fast? (More defects, cloudy appearance.) Compare your fast-grown and slow-grown crystals. Which are clearer and more geometrically perfect?
- Write a crystallography paper: document your seed crystal growth process, crystal system identification, geometric measurements, defect analysis, and research on crystal technology applications.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Grow a large single crystal using the seed crystal technique
- Identify crystal systems and verify crystal geometry through measurement
- Research and explain how crystal properties are applied in modern technology
Safety and evidence note
Read the full activity before beginning. An adult should supervise tools, heat, food, outdoor work, movement, and experiments as appropriate. Completion records that the activity was done; the child’s explanation, work sample, photo, or demonstration is stronger evidence of learning than a completion check alone.
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