Chem-ME-stry Dichotomous Key Activity
Background:
A dichotomous key is a tool that can be used to easily identify things (usually living organisms).
Dichotomous means “divided in two parts.” A dichotomous key consists of a series of two part
statements that describe characteristics. At each step of a dichotomous key the user is
presented with two choices. As the user makes a choice about a particular characteristic, they
are led to a new branch of the key. Eventually, the user will be led to the name of the thing that
they are trying to identify.
Purpose:
The purpose of this assignment is to create a dichotomous key of matter in order to demonstrate
how characteristics and their relationships shape identity. In addition, you will also show how
you are connected to chemistry by including yourself in your own dichotomous key.
Your Task:
1. Choose at least 10 different examples of matter. YOU (or humans in general) must be
one example. You should also have other examples of elements, compounds, and
mixtures in your list. If you need ideas, use your periodic table or the provided list of
common compounds.
2. Carefully examine and think about the characteristics of each example in your list. You
may need to look up some of the chemical and physical characteristics of your examples
if you do not know them.
3. Develop a spider key:
a. Consider your entire list. Separate everything into two groups based on a single
distinguishing characteristic. Record this characteristic.
b. Then, continue to separate each of the groups, recording the defining
characteristics as you go, until each object has its own separate set of
characteristics.
ESMS Teachers
NOT on 2nd floor of JM
On 2nd floor of JM
MR. DUFFY
Teaches science
Does NOT teach science
MR. EASTMAN
Teaches only 8th grade science
MS. DELONG
Teaches other science grades
Teaches grades other than 7th
MS. HAYNES
Only teaches 7th grade
Life Science only
MS. TUCKER
Other subjects
MS. BOYCE
4. Use your spider key to develop your dichotomous key in the traditional written format.
(Note: There should be one fewer step than the number of items identified in any dichotomous key
[10 items = 9 steps, 15 items = 14 steps, etc])
1.a. Is a teacher on the 2nd floor of JM…………....go to step 2
b. Is NOT a teacher on the 2nd floor of JM………MR. DUFFY
2.a. Teaches science……………………..…go to step 3
b. Does NOT teach science………………MR. EASTMAN
3.a. Only teaches 8th grade………………...MS. DELONG
b. Teaches grades other than 8th…………go to step 4
4.a Only teaches 7th grade………………. go to step 5
b. Teaches grades other than 7th ………. MS. HAYNES
5a. Only teaches Life Science …………..............MS. TUCKER
b. Teaches subjects other than Life Science……MS. BOYCE
Finished Product
1. Please type your finished, traditionally-written dichotomous key.
2. Neatly draw or type your finished spider web
3. Find a professional and creative way to display 1 and 2 above.
Hints
Consider the vocabulary we have learned so far in our chemistry unit. Try incorporating these
terms into your dichotomous key. Also consider some of the chemicals we have seen, used, or
mentioned. Try incorporating those or research some of your own.
Matter
Element
Atom
Compound
Mixture
Homogeneous mixture
Heterogeneous mixture
Physical properties
Chemical properties
Solid
Amorphous solid
Crystalline solid
Liquid
Viscosity
Gas
Physical changes
Chemical changes
Due Date
On or before Friday, February 21st
Grading Rubric
Endothermic reaction
Exothermic reaction
Solution
Solute
Solvent
Concentrated
Dilute
A DICHOTOMOUS KEY
THAT “MATTERS”