May/June 2017 – Vol. 29 No. 7

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 Annual Conference Early Bird Rates End July 14

Posted: Wednesday, July 12th, 2017

by Jessica Sawko

Teachers engaged in workshop activity

Teachers engaging in hands-on learning during a workshop at the 2016 CSTA conference.

Don’t miss your chance to register at the early bird rate for the 2017 CSTA Conference – the early-bird rate closes July 14. Need ideas on how to secure funding for your participation? Visit our website for suggestions, a budget planning tool, and downloadable justification letter to share with your admin. Want to take advantage of the early rate – but know your district will pay eventually? Register online today and CSTA will reimburse you when we receive payment from your district/employer. (For more information on how that works contact Zi Stair in the office for details – 916-979-7004 or

New Information Now Available On-line:

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.

Goodbye Outgoing and Welcome Incoming CSTA Board Members

Posted: Wednesday, July 12th, 2017

Jill Grace

Jill Grace, CSTA President, 2017-2019

On July 1, 2017 five CSTA members concluded their service and four new board members joined the ranks of the CSTA Board of Directors. CSTA is so grateful for all the volunteer board of directors who contribute hours upon hours of time and energy to advance the work of the association. At the June 3 board meeting, CSTA was able to say goodbye to the outgoing board members and welcome the incoming members.

This new year also brings with it a new president for CSTA. As of July 1, 2017 Jill Grace is the president of the California Science Teachers Association. Jill is a graduate of California State University, Long Beach, a former middle school science teacher, and is currently a Regional Director with the K-12 Alliance @ WestEd where she works with California NGSS K-8 Early Implementation Initiative districts and charter networks in the San Diego area.

Outgoing Board Members

  • Laura Henriques (President-Elect: 2011 – 2013, President: 2013 – 2015, Past President: 2015 – 2017)
  • Valerie Joyner (Region 1 Director: 2009 – 2013, Primary Director: 2013 – 2017)
  • Mary Whaley (Informal Science Education Director: 2013 – 2017)
  • Sue Campbell (Middle School/Jr. High Director: 2015 – 2017)
  • Marcus Tessier (2-Year College Director: 2015 – 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.

Finding My Student’s Motivation of Learning Through Engineering Tasks

Posted: Wednesday, July 12th, 2017

by Huda Ali Gubary and Susheela Nath

It’s 8:02 and the bell rings. My students’ walk in and pick up an entry ticket based on yesterday’s lesson and homework. My countdown starts for students to begin…3, 2, 1. Ten students are on task and diligently completing the work, twenty are off task with behaviors ranging from talking up a storm with their neighbors to silently staring off into space. This was the start of my classes, more often than not. My students rarely showed the enthusiasm for a class that I had eagerly prepared for. I spent so much time searching for ways to get my students excited about the concepts they were learning. I wanted them to feel a connection to the lessons and come into my class motivated about what they were going to learn next. I would ask myself how I could make my class memorable where the kids were in the driver’s seat of learning. Incorporating engineering made this possible. Learn More…

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Written by NGSS Early Implementer

NGSS Early Implementer

In 2015 CSTA began to publish a series of articles written by teachers participating in the California NGSS k-8 Early Implementation Initiative. This article was written by an educator(s) participating in the initiative. CSTA thanks them for their contributions and for sharing their experience with the science teaching community.

State Schools Chief Tom Torlakson Unveils Updated Recommended Literature List

Posted: Wednesday, July 12th, 2017

SACRAMENTO—State Superintendent of Public Instruction Tom Torlakson unveiled an addition of 285 award-winning titles to the Recommended Literature: Prekindergarten Through Grade Twelve list.

“The books our students read help broaden their perspectives, enhance their knowledge, and fire their imaginations,” Torlakson said. “The addition of these award-winning titles represents the state’s continued commitment to the interests and engagement of California’s young readers.”

The Recommended Literature: Prekindergarten Through Grade Twelve list is a collection of more than 8,000 titles of recommended reading for children and adolescents. Reflecting contemporary and classic titles, including California authors, this online list provides an exciting range of literature that students should be reading at school and for pleasure. Works include fiction, nonfiction, poetry, and drama to provide for a variety of tastes, interests, and abilities. Learn More…

Written by Guest Contributor

From time to time CSTA receives contributions from guest contributors. The opinions and views expressed by these contributors are not necessarily those of CSTA. By publishing these articles CSTA does not make any endorsements or statements of support of the author or their contribution, either explicit or implicit. All links to outside sources are subject to CSTA’s Disclaimer Policy:

Teaching Science in the Time of Alternative Facts – Why NGSS Can Help (somewhat)

Posted: Wednesday, July 12th, 2017

by Peter A’Hearn

The father of one of my students gave me a book: In the Beginning: Compelling Evidence for Creation and the Flood by Walt Brown, Ph. D. He had heard that I was teaching Plate Tectonics and wanted me to consider another perspective. The book offered the idea that the evidence for plate tectonics could be better understood if we considered the idea that beneath the continent of Pangaea was a huge underground layer of water that suddenly burst forth from a rift between the now continents of Africa and South America. The waters shot up and the continents hydroplaned apart on the water layer to their current positions. The force of the movement pushed up great mountain ranges which are still settling to this day, resulting in earthquakes along the margins of continents. This had happened about 6,000 years ago and created a great worldwide flood. Learn More…

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Written by Peter AHearn

Peter AHearn

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