Yakima WATERS Mini Lesson
Growing and Dissolving Crystals with Vinegar, a Dilute Acid
Targets and Assessment
WA Science GLEs Addressed:
 4-5 INQC Investigate
 4-5 INQF Models
Lesson Parameters
Content Area: Chemistry, Geology
Overview: In this lesson, students grow aragonite
crystals on dolomite and dissolve limestone with
vinegar, a weak acid. This lesson mimics the
processes responsible for cave system formation.
Cave systems are an important source of
groundwater for some people in the United
States.
Grade Level: 5, 6
Assessments:
 Can students explain crystal formation on
dolomite from evaporation?
 Can students make the connection
between this exercise and limestone –
acidic water interaction?
Suggested Time: Day 1 – 45 minutes; Day 2 – 15
minutes
Special Materials:
 dolomite, limestone, vinegar, small pie tins
Learning Outcomes:
Knowledge:
 Students will be able to explain that acidic rain and water aids in cave formation.
 Students will explain that caves are related to sinkholes, but an important “underground
storage tank” for water in places like Texas, Florida, and Tennessee.
 Students will be able to predict why crystals formed on the dolomite after evaporation
of vinegar.
Skill:
 Students will be able to represent visual observations with labeled sketches.
 Students will learn how to measure an object and scale it on a sketch of that object.
Science Concept Background:
This lesson works well with the pollution unit. Students have just learned about acid rain and
have talked about pH. During this lesson, students learn how acid rain (vinegar) can also
change the geology of cave systems. They will also learn that some places like Texas and
Tennessee have aquifers that rely on groundwater stored in cave systems. Before the lesson,
students will view a presentation on the cave formations in Carlsbad Caverns, New Mexico.
Procedure:
Engage (~5 minutes) – Presentation on Carlsbad cavers, background/introduction information.
Materials:
1 sample of limestone per group
1 sample of dolomite per group
Enough vinegar to cover 2/3 of each sample
1 pie tin
Key questions:
Hypothesis 1: What will happen to the dolomite when it soaks in the vinegar for a day? Two
days?
Hypothesis 2: What will happen to the limestone when it soaks in the vinegar for a day? Two
days?
Part1:
1.
2.
3.
Dolomite (~10 minutes)
Place the dolomite in the pie tin and add vinegar until it is about two thirds covered.
Place the pie pan in a warm and sunny location to encourage evaporation of the vinegar.
What does the mineral look like? Sketch and record your observations in the Dolomite
Table.
Part 2: Limestone
1. Place the limestone in a separate pie tin.
2. Add vinegar until the limestone is about two thirds covered.
3. What happens to the limestone when it contacts the vinegar? What do you see, hear, and
smell? Record your observations in the Limestone Table.
Extension(s):
Black light exercise - The crystals that form on the dolomite are called aragonite and should
fluoresce under a black light.
Teaching Tips:
Students will be amazed at the growth of the crystals, but will not understand how they grew.
Some of the students understand that the salty ocean leaves behind salt crystals when the
water evaporates so I used this analogy to explain to them how aragonite crystals are left
behind when the vinegar is allowed to evaporate.
Supplements:
See “Cave Systems and Groundwater” powerpoint presentation for introduction and background
information.This lesson was modified from “Don’t Mess With TAKS” B.H. Hixson, pages 6667.
Worksheets attached
Author: Sarah Nagorsen, Yakima WATERS Project, CWU, Fall 2009
Growing and Dissolving Crystals
with Vinegar, a Dilute Acid
Introduction:
Hypothesis: Using what you now know about vinegar and the mineral dolomite, form a
hypothesis (make a prediction) about what will happen to the dolomite and limestone when it
soaks in the vinegar.
Hypothesis 1: What will happen to the dolomite when it soaks in the vinegar for a day? Two
days?
______________________________________________________________________________
Hypothesis 2: What will happen to the limestone when it soaks in the vinegar for a day? Two
days?
______________________________________________________________________________
______________________________________________________________________________
Experiment:
Materials:
1 sample of limestone
1 sample of dolomite
Enough vinegar to cover both samples by 2/3
1 pie tin
water
Procedure:
Part1: Dolomite
1. Place the dolomite in the pie tin and add enough vinegar to cover 2/3 of the dolomite.
2. Place the pie pan in a warm and sunny location.
3. What does the dolomite look like? Sketch the rock and record your observations in the
Dolomite Table.
Observation Date and Time
Day 1: Observation after vinegar is
added
Day 1: Observation later in the day
Day 2: Observation after dolomite has
soaked over night
Dolomite Table
Sketch of dolomite (include cm scale and labels)
Part 2: Limestone
4. Place the limestone in a separate pie tin.
5. Pour enough vinegar into the pie tin to cover 2/3 of the limestone.
6. What happens to the limestone when it contacts the vinegar? What do you see, hear, and
smell? Record your observations in the Limestone Table.
Limestone Table
Observation Date and Time
Day 1: Observation after vinegar is
added
Day 1: Observation later in the day
Day 2: Observation after limestone
has soaked over night
Sketch of limestone (include cm scale and labels)
Questions:
Dolomite:
1. What happened to the dolomite after it soaked in the vinegar overnight? Has the amount
of vinegar changed?
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2. The crystals that grew on the dolomite are a mineral called “aragonite.” Why did crystals
form on the dolomite after it soaked in the vinegar?
_____________________________________________________________________________
_____________________________________________________________________________
Limestone:
3. What happens if acidic rain and water contacts limestone on the surface of the earth or
underground?
______________________________________________________________________________
______________________________________________________________________________
_____________________________________________________________________________