PHYSICAL AND CHEMICAL PROPERTIES AND CHANGES
Objectives:
· To observe the chemical and physical properties of substances
· To decide whether certain observed changes are physical or chemical
· To perform certain lab techniques such as filtration and evaporation
Procedure:
Part A: Physical Properties of Matter
1. Obtain seven small sheets of paper. Label each with the name of one of the following substances: magnesium, sulfur, iron, sodium bicarbonate, sodium chloride, sucrose, and sand. Obtain a small piece of magnesium and pea size samples of the others and place each on the appropriate sheet of paper.
2. Examine each substance. Note the physical state, color and odor. Record your observations.
3. Test the effect of a magnet on each substance by passing the magnet under the sheet of paper. Do not dip the magnet directly into the material. Record your observations.
4. There will be test tubes in a test tube rack on the teacher’s desk showing each substance in water. Observe the solubility of each substance and record this information in the data table.
Part B: Causing a Physical or Chemical Change
5. Combine the remaining samples of iron filings and sulfur. Mix the samples thoroughly using a scoopula. Examine the mixture. Record your observations. Move a magnet under the paper below the mixture and examine it again. Record your observations. Throw this mixture in the trash can.
6. Combine the remaining samples of sodium chloride and sand. Examine the mixture and test the effect of a magnet. Record your observations. Transfer the salt/sand mixture to a 100 mL beaker. Add 30 mL of tap water and stir the mixture thoroughly with a glass rod. Record your observations.
Filter the mixture as follows:
Fold a piece of filter paper in quarters. Open the paper to form a cone with one thickness of paper on one side and three thicknesses on the other. (See figure 2-1.) Put the filter paper in a funnel and place the funnel in a ring clamp attached to a ring stand. (See figure 2-2.) Place another beaker below the funnel and pour the salt/sand/water mixture into the funnel. The liquid that passes through is called the filtrate.
Pour a small amount of the filtrate into an evaporating dish. Set this dish on a wire gauze or clay triangle supported by a ring clamp attached to a ring stand. Using a gas burner and keeping your face away from the evaporating liquid, heat the dish gently until the filtrate has completely evaporated. Allow the dish to cool. While the dish is cooling, remove the filter paper from the funnel. Examine both the dry residue in the evaporating dish and the wet residue on the filter paper. Record your observations. Discard the filter paper into the trash can.
7. CAUTION: Do not look directly at the burning magnesium. Its flame is very bright and can damage your eyes. Keep burning magnesium at arm’s length at all times and do not inhale the fumes that are given off in the combustion process.
Place a watch glass on the laboratory bench close to the gas burner. Light your burner. Use crucible tongs to grasp one end of a 5 cm strip of magnesium ribbon and hold this strip in the burner flame until the magnesium ignites. Position the magnesium so that the product of the combustions will fall onto the watch glass. Compare the appearance of the product with that of the original magnesium ribbon. Record your observations.
8. Put a 1 cm strip of magnesium ribbon into a clean test tube. Place the test tube in a rack. Add 10-12 drops of 6 M hydrochloric acid to the tube. CAUTION: hydrochloric acid is corrosive. Record your observations. Touch the bottom of the test tube to the palm of your hand. Record any differences in temperature. Wash the contents of the tube down the sink.
9. Transfer a pea size sample of sodium bicarbonate to a clean test tube. Carefully add 5 drops of 6 M hydrochloric acid one drop at a time. CAUTION: hydrochloric acid is corrosive. Touch the bottom of the test tube to your palm. Record your observations. The contents of the test tube may be washed down the sink.
Organizing your formal lab report:
Each underlined section below should appear on its own page in your formal report. Everything must be typed, even the data tables. You may collaborate with your lab partner, but you may not turn in identical reports. You may use any font you choose, and you may get as creative as you like, as long as you follow the format below. Written paragraphs must be left-justified. If used, formulas must have subscripts typed correctly. Please use spell-check and label each page (other than the title page) appropriately. Use portrait instead of landscape format.
Title (5 points)
This is the title of the lab from your lab handout. The title page should also include your name, block, and partner’s name.
Purpose (10 points)
The purpose should state in complete sentences why we are doing the lab. What are our goals in completing the lab? These goals are found in the objectives section on the lab sheet.
Introduction (15 points)
The introduction should explain the general concepts of the lab. For this lab it should include the definitions of physical and chemical properties as well as physical and chemical changes. It should explain how the procedures of this lab will allow the purposes to be accomplished. (How will you observe physical and chemical properties and changes?) It should be a well-written paragraph, not a series of definitions and should include no data. It should be written from the perspective of someone who has not yet done the lab.
Data Table Part A (10 points)
Make a data table for each of the elements and compounds you investigated during part A. (There are SEVEN!)
Data Table Part B (20 points)
For each of the following systems, describe your observations in a table format.
· Fe and S mixture—general appearance; effect of magnet
· NaCl and sand mixture—general appearance; effect of magnet
· NaCl, sand, and water mixture—general appearance; solubility of sand, salt
· Appearance of wet residue on filter paper
· Appearance of dry residue on evaporating dish
· Mg burned in air—general observations; appearance of original Mg vs. burned Mg
· Mg reacted with HCl—general observations; note any temperature change
· NaHCO3 reacted with HCl—general observations; note any temperature change
Discussion (25 points)
State whether each of the following shows a chemical or a physical change and give specific evidence from your observations to justify your answer.
- the mixing of iron and sulfur
- mixing of salt, sand, and water
- the burning of magnesium
- mixing magnesium with hydrochloric acid
- mixing sodium bicarbonate with hydrochloric acid
Conclusion (15 points)
This paragraph will restate the purpose and tell whether the objectives were met using specific results from the lab. (For example, did you see a physical change? What was it?) As part of your conclusion use your data to describe two physical properties and two chemical properties of Mg.
Data Table Part A
Substance and Formula / Physical State(Solid, Liquid, Gas) / Color / Odor / Solubility in Water / Effect of Magnet
sulfur, S
iron filings, Fe
sodium bicarbonate, NaHCO3
sodium chloride, NaCl
sucrose, C12H22O11
sand, SiO2
magnesium, Mg
Data Table Part B
System / ObservationsFe and S mixture
NaCl and sand mixture
NaCl, sand, and water mixture
Appearance of wet residue on filter paper
Appearance of dry residue on evaporating dish
Mg burned in air
Mg reacted with HCl
NaHCO3 reacted with HCl