September/October 2017 – Vol. 30 No. 1

Chemicals and Their Properties Lab

Posted: Tuesday, March 1st, 2011

by Jeff  Bradbury and Patricia Buchanan

Name ____________________

Date _____________________

Partner’s Name ____________

Question: The work of a crime scene investigator (CSI) is to identify certain found liquids or solids in an investigation, how could we find out the identity of an unknown substance?

Purpose: To learn how to classify matter and its changes.

Part 1 Introduction:

Background Information:

1) A pure substance is a sample of matter that has a definite, fixed composition, and the same properties throughout the sample.  Each pure substance has its own set of characteristic properties.

Physical properties can be observed without changing the chemical composition of the substance.  Common physical properties that can be measured without changing the chemical composition are color, melting point, boiling point, solubility, and density.  Taste and odor are usually considered to be physical properties although they depend on the physiology of the person making the observations.

Physical changes do not cause a change in chemical composition, but only a change in appearance.  When a substance simply changes from a solid to a liquid, liquid to a gas or vice-versa (liquid water to solid water, for example) without a change in composition, it is a change in state.  This is a physical change.  (The three physical states are:  gas, liquid, and solid).

Chemical properties describe the ability of a substance to react and change into another substance with a different chemical composition.  The new substance would have new properties.

2) Evidence that a chemical change is taking place includes:

a.  A color change

b.  A solid product, a precipitate is formed

c.  A gas is formed

d.  Energy such as heat, light or electricity is produced.


In today’s lab you will observe some physical properties of elements and some physical and chemical changes. You will be working in groups of 2.

Procedure, Observations, and Data:


Safety goggles must be worn at all times

Hydrochloric acid (HCl) and sodium hydroxide (NaOH) can harm eyes, skin, and clothing. Handle with care. Any acid spilled on the skin should be rinsed with a large volume of water for 15 minutes.

Wash your hands before you leave the lab.

Do not take reagent bottles from the reagent bench to your work station.

Do not pour anything back into a reagent bottle. Offer extra chemical to another student

Do not stick anything into a reagent bottle.

Always clean glassware and spot plates with distilled/deionized water.

Using Chemical and Physical Changes to Identify an Unknown Substance:

At the reagent bench are samples of 7 common substances.  Your instructor will assign you an unknown, which is the same as one of the 7 known substances.  Based on the observations of the chemical and physical properties of the known and unknown substances, you will determine the identity of the unknown.

Procedures 3-5 do not need to be done in order.  You will perform all of the tests on the unknown that you perform on each of the known samples.

1. Observe each sample, including the unknown, and then record your observations as to the color, texture and any other important properties in table 1.

2. In a spot plate place small pea-sized amounts of each substance in 2 different rows of wells. Be careful to note which substance is in which well. Do not use more than a small pea-sized amount, or it will be difficult to perform the tests. (On a paper towel write the name of each substance in the order it is placed in your spot plate, and place this paper towel next to the spot plate.)

3. a. Into the first row of wells of the different substances, put about 1 ml of de-ionized water.  See if the substances dissolve completely or partially, or change in any other way. Record any evidence of change that occurs in table 1.

b. In the row of wells that contains the substances mixed with water, put 3 drops of universal indicator. Record any evidence of change in table 1.

4. In the other row of wells containing the samples put 3 drops of dilute acetic acid (vinegar) and record any evidence of change in table 1 below.

5. Cover your wire gauze with a piece of the aluminum foil that is set out on the reagent bench.  Place about pea-sized amounts of each substance onto the foil covered gauze. Make sure there is plenty of space between each sample on the foil.  Place the gauze on the ring stand and ring apparatus that is in the fume hood.   Light the burner and place the heat under each sample to see if any change occurs. Record any evidence of change in table 1.

Using the data that you recorded in table 1, determine the identity of the unknown sample and answer the questions that follow the table.

Waste: Rinse spot plates in the sink.  Clean spot plates with tap water then deionized water. When aluminum foil has cooled. Wad it up and throw it in the trash.

Table 1: Determining the identity of an Unknown substance

Appearance (1) Reaction with water  (2) Reaction with universal indicator (3) Reaction with vinegar  (4) Reaction with heat   (5)
Sodium Chloride
Sugar (Sucrose)
Baking Powder
Baking Soda

(Sodium Bicarbonate)

Citric Acid
White Flour
Calcium Carbonate
Unknown #

Unknown #     ____________________

Based on you observations in the above table identify the unknown _____________________

Explain the evidence for your answer to the above question:


1.  Explain the difference between a chemical and physical change? (You can use examples from this lab in your explanation.)

2. What was it that you did today that helped you see the difference between a chemical and physical change?

3. What happened when vinegar was added to the powders?


Jeff Bradbury is a professor of chemistry at Cerritos College in Norwalk and is community college director for CSTA; Patricia Buchanan is the Cal Grip Grant Project Assistant at Cerritos College.  The original idea for this activity came from the Los Angeles County Office of Education 15 years ago, which the authors modified.

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

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CSTA Is Now Accepting Nominations for Board Members

Posted: Friday, November 17th, 2017

Current, incoming, and outgoing CSTA Board of Directors at June 3, 2017 meeting.

Updated 7:25 pm, Nov. 17, 2017

It’s that time of year when CSTA is looking for dedicated and qualified persons to fill the upcoming vacancies on its Board of Directors. This opportunity allows you to help shape the policy and determine the path that the Board will take in the new year. There are time and energy commitments, but that is far outweighed by the personal satisfaction of knowing that you are an integral part of an outstanding professional educational organization, dedicated to the support and guidance of California’s science teachers. You will also have the opportunity to help CSTA review and support legislation that benefits good science teaching and teachers.

Right now is an exciting time to be involved at the state level in the California Science Teachers Association. The CSTA Board of Directors is currently involved in implementing the Next Generations Science Standards and its strategic plan. If you are interested in serving on the CSTA Board of Directors, now is the time to submit your name for consideration. Learn More…

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

State Schools Chief Tom Torlakson Announces 2017 Finalists for Presidential Awards for Excellence in Mathematics and Science Teaching

Posted: Wednesday, September 20th, 2017

SACRAMENTO—State Superintendent of Public Instruction Tom Torlakson today nominated eight exceptional secondary mathematics and science teachers as California finalists for the 2017 Presidential Awards for Excellence in Mathematics and Science Teaching (PAEMST).

“These teachers are dedicated and accomplished individuals whose innovative teaching styles prepare our students for 21st century careers and college and develop them into the designers and inventors of the future,” Torlakson said. “They rank among the finest in their profession and also serve as wonderful mentors and role models.”

The California Department of Education (CDE) partners annually with the California Science Teachers Association and the California Mathematics Council to recruit and select nominees for the PAEMST program—the highest recognition in the nation for a mathematics or science teacher. The Science Finalists will be recognized at the CSTA Awards Luncheon on Saturday, October 14, 2017. Learn More…

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

Thriving in a Time of Change

Posted: Wednesday, September 13th, 2017

by Jill Grace

By the time this message is posted online, most schools across California will have been in session for at least a month (if not longer, and hat tip to that bunch!). Long enough to get a good sense of who the kids in your classroom are and to get into that groove and momentum of the daily flow of teaching. It’s also very likely that for many of you who weren’t a part of a large grant initiative or in a district that set wheels in motion sooner, this is the first year you will really try to shift instruction to align to the Next Generation Science Standards (NGSS). I’m not going to lie to you, it’s a challenging year – change is hard. Change is even harder when there’s not a playbook to go by.  But as someone who has had the very great privilege of walking alongside teachers going through that change for the past two years and being able to glimpse at what this looks like for different demographics across that state, there are three things I hope you will hold on to. These are things I have come to learn will overshadow the challenge: a growth mindset will get you far, one is a very powerful number, and it’s about the kids. Learn More…

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Written by Jill Grace

Jill Grace

Jill Grace is a Regional Director for the K-12 Alliance and is President of CSTA.

If You Are Not Teaching Science Then You Are Not Teaching Common Core

Posted: Thursday, August 31st, 2017

by Peter A’Hearn 

“Science and Social Studies can be taught for the last half hour of the day on Fridays”

– Elementary school principal

Anyone concerned with the teaching of science in elementary school is keenly aware of the problem of time. Kids need to learn to read, and learning to read takes time, nobody disputes that. So Common Core ELA can seem like the enemy of science. This was a big concern to me as I started looking at the curriculum that my district had adopted for Common Core ELA. I’ve been through those years where teachers are learning a new curriculum, and know first-hand how a new curriculum can become the focus of attention- sucking all the air out of the room. Learn More…

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Written by Peter AHearn

Peter AHearn

Peter A’Hearn is the Region 4 Director for CSTA.

Tools for Creating NGSS Standards Based Lessons

Posted: Tuesday, August 29th, 2017

by Elizabeth Cooke

Think back on your own experiences with learning science in school. Were you required to memorize disjointed facts without understanding the concepts?

Science Education Background

In the past, science education focused on rote memorization and learning disjointed ideas. Elementary and secondary students in today’s science classes are fortunate now that science instruction has shifted from students demonstrating what they know to students demonstrating how they are able to apply their knowledge. Science education that reflects the Next Generation Science Standards challenges students to conduct investigations. As students explore phenomena and discrepant events they engage in academic discourse guided by focus questions from their teachers or student generated questions of that arise from analyzing data and creating and revising models that explain natural phenomena. Learn More…

Written by Elizabeth Cooke

Elizabeth Cooke

Elizabeth Cooke teaches TK-5 science at Markham Elementary in the Oakland Unified School District, is an NGSS Early Implementer, and is CSTA’s Secretary.