Lab 1: (Physical and Chemical Change) Name
Purpose: To investigate the criteria used to distinguish between physical and chemical changes in matter.
Background:
Have you ever thought of your eyes as powerful tools for studying chemistry? Many of the properties of matter and the changes it undergoes can easily be determined through careful observation.
Physical properties include color, odor, density, solubility, and the state of matter.
Chemical properties describe the changes that take place when new substances are formed during a chemical reaction.
When matter undergoes a change, it is classified as either a physical change or chemical change.
During a physical change, only the size, temperature, or physical state of the substance change. There is no change in the composition of the substance. In other words, no new substances are produced during a physical change.
During a chemical change, one or more new substances are formed. These changes show up as changes in color, odor, energy (heat or light given off or absorbed), or in the production of a gas and the resulting products have different properties than the original materials.
For example: Iron metal left outside will rust. The new substance, rust, is iron(III) oxide, Fe2O3 (s), and is a result of iron metal (Fe) reacting with oxygen gas (O2) from the air as shown by the following chemical equation.
4 Fe(s) + 3 O2 (g) → 2 Fe2O3 (s)
solid iron oxygen iron(III) oxide or “rust”
Rust has different properties than iron. It is a different color and is no longer magnetic. It also crumbles when scratched and does not conduct heat or electricity as well as the original iron. The rust is also heavier than the original iron because it has the added mass of oxygen from the air.
In this experiment you will observe a variety of materials and describe their physical properties. You will then mix some of the substances or heat them to see if they undergo any changes. Based upon your observations, you will determine whether the changes are physical changes or chemical changes.
Materials:
q Lab Apron
q Safety Goggle
q Plastic weighing tray
q Beakers
q Large test tubes
q Evaporating dish
q Hot plate
q Funnel and filter paper
Chemicals
q Iron filings, Fe
q Sodium chloride, “table salt”, NaCl
q Sand, SiO2
q 6M hydrochloric acid, HCl (corrosive, toxic, handle with extreme care)
q Marble chip made of calcium carbonate, CaCO3 .
q Cut copper penny
Safety Alert:
In this lab observe all precautions, especially the ones listed below and in the procedures.
q Protect your eyes! Wear your safety goggles with all steps.
o Hydrochloric acid is very corrosive, highly toxic, and can cause severe burns. Wear you lab apron and protective gloves when working with this substance. Notify teacher immediately of any spills and wash off your table, glassware, and your hands at the end of the lab.
q Protect your lungs!
o Do not inhale the smoke or gases produced during a chemical reaction.
q Never taste chemicals!
o Treat all chemicals as toxic.
o Wash hands after handling chemicals.
q Protect your hands!
o Wear gloves when handling strong acids.
o Do not touch hot glass or metal.
q Protect our environment!
o Dispose of all materials according to the instructions of your teacher.
Lab Technique:
Filtering a mixture:
q Fold a piece of filter paper and prepare a filtration setup as shown in Figures 2.1 and 2.2.
q Filter the mixture and exam the filtrate and wet residue left on the filter paper. Record your observations in your Data Table.
Lab 1: (Physical and Chemical Change) Name
(Safety goggles MUST be worn during all steps)
Iron, sand, sodium chloride, and water:
1. Obtain a mixture of iron, sand, and sodium chloride from your instructor.
2. Discuss the best way to separate these substances and come up with a list of procedures to follow.
Note: If you use a magnet, keep it in the plastic bag to make it easier to remove anything that sticks to the magnet.
Describe your procedures for separating these substances. Continue numbers as needed. Use these procedures to separate the mixture.
3. / Data and Observations:
Reactions with the acid Hydrochloric acid, HCl:
Note: Hydrochloric acid is very corrosive, highly toxic, and can cause severe burns. Wear you lab apron and protective gloves when working with this substance.
Hydrochloric acid added to a marble chip made of calcium carbonate, CaCO3 (s)
1. Place a marble chip into a large test tube.
2. Add 10 to 20 drops of 6 M hydrochloric acid to the chip.
3. Touch the bottom of the test tube during the reaction to see if there are any temperature changes.
4. Rinse your acid waste into the designated acid waste beaker. Clean your test tube with tap water and a test tube brush. Place upside down on the test tube rack.
5. Record your observations in the space to the right of these procedures.
Hydrochloric acid added to a cut up copper penny.
1. Place a cut penny into a 50 mL beaker.
2. Using a 10 mL graduated cylinder, measure out approximately 8 mL of the 6 M hydrochloric acid and add it to the copper penny.
3. Record your observations in the space provided to the right.
4. Rinse your acid waste into the designated acid waste beaker. Clean your beaker with tap water and a test tube brush. Dry it out with a paper towel and wipe your lab table down with a wet cloth.
5. Make sure all equipment used in the experiment is clean and ready for the next class.
6. Follow your teacher’s instructions for proper disposal of all materials. / Data and Observations
Lab 1: (Physical and Chemical Change) Name
Conclusion /Analysis Questions:
- Describe the difference between a physical change and a chemical change.
- What criteria did you use to recognize when chemical changes took place.
- Indicate whether each mixing resulted in a physical change or a chemical change or both. Justify your answer.
System / Type of change
(circle one) / Justification
Mixing iron , sand, and salt. / Chemical change
Physical change
Both
Mixing hydrochloric acid with marble chips. / Chemical change
Physical change
Both
Mixing hydrochloric acid with a cut penny. / Chemical change
Physical change
Both
4. Was the copper penny made of pure copper or a mixture of substances? How can you tell?