Chemical and Physical Changes

LISTEN CAREFULLY TO ALL SAFETY INSTRUCTIONS PROVIDED

  • Hair must be tied back (we are working with fire)
  • Do not pick up broken glass or touch test tubes that have been heated.
  • Goggles should be worn at all times.
  • Do not look directly at the burning magnesium strip (warn your peers).
  • Do not taste, sniff or eat anything in the lab.
  • Keep your personal belongings out of walkways.

Background: the world around is in a state of flux, matter is constantly changing. Things grow, change colors, die and constantly transform. We classify these changes as either physical or chemical changes.

Chemical Change: One or more substances changes into something new. The internal properties of a substance change. Example: Burning Paper (combustion in general), digestion of food, rusting, fireworks exploding, cooking.

Physical Change:The internal composition of something does not change. It remains the same chemically after a change. Examples: Ripping paper, crushing a can, cutting hair, breaking chalk, molding Play-Doh, cracking an egg.

Phase Changes:Changes of state are PHYSICAL CHANGES. When ice melts it is still H20. When liquid water evaporates into water vapor gas, it is still H2O.

5 Signs A Chemical Change might have occurred

  1. Transfer of Energy (temperature change…endothermic/exothermic reactions)
  2. Color Change (ex. Fruit changes color over time, this is a chemical change)
  3. Formation of a Precipitate (a solid particle when two solutions are mixed)
  4. Production of Gas (gas bubble indicate a chemical change might have occurred)
  5. Production of an Odor (an egg rotting, smell of the atmosphere after a lightning storm)

Procedure: We are going to create and observe a number of changes in lab. You will classify them as chemical or physical based upon your observations. Complete the assigned tasks and fill in the data table.
EXPERIMENTS

Station 1: Heating Sugar

Place a small amount of sugar in a test tube. Secure it to a ring stand and heat it up using the portable burners. Record your observations. Sugar remains hot for a long time after the heat is removed. Do not touch the test tube with your hands until it thoroughly cools. Record your observations.

Station 2: Surfing Water

Using a disposable pipette place a drop of water on the hot plate. Observe what happens. Record your observations. Be careful, the hot plate is over 500 degrees Fahrenheit.

Station 3: Magnesium

Take a 2” inch piece of magnesium coil. Hold it with a pair of tongs and use the portable burner to light one end of it on fire. Record your observations. DO NOT LOOK DIRECTLY AT IT. THE LIGHT WILL BE VERY BRIGHT! Record your observations.

Station 4: Hulk Smash

Take a piece of chalk and put it in a mortar and crush it with a pestle. Record your observations.

Station 5: Metals and Acid

Place a small piece of zinc or magnesium in a test tube. Attach it securely to a ringstand. Add a small amount of hydrochloric or sulfuric acid. Record your observations. Acid is dangerous. Wear goggles and rinse your hand immediately if you come in contact with it. Carefully touch the outside of the test tube. Is it hot or cold?

Station 6: Eggzactly Like that

Put an egg in a beaker/clear plastic cup and cover it with acetic acid/or vinegar and observe what happens. This will be labeled with your group name and left overnight in lab.

Station 7: Formation of a Precipitate.

Using a reaction plate put a few drops of Silver Nitrate into a well. Add a few dropsof potassium chromate and record your observations. DO NOT MIX PIPETTES.

Station 8: Origami

Using colored paper, create something with it.

CLEAN UP AFTER YOURSELVES. Return everything to where it belongs.

Chemical and Physical Changes Lab
Station Name: / Type of Change / Observations/Evidence
Heating Sugar
Surfing Water.
Magnesium
Hulk Smash!
Metals and Acid
Eggzactly
Precipitate
Origami

1) If alcohol evaporates, is it a chemical or physical change?

2)List some clues that might indicate a chemical change has occurred.

3) Identify the following as either chemical or physical changes?

  • Cooking an Egg
  • Ripping Paper
  • Lighting a Match
  • A C₃H₈O molecule evaporating
  • Ice Melting
  • Mixing Baking soda and vinegar
  • Getting a suntan

Essay: Compare and Contrast Chemical and Physical Changes. Be sure to define both terms and provide three examples of each that are not mentioned in this lab.

Station 1: Baking Soda Volcano

Take a piece of Play Dough and mold it into a kitten, dinosaur or some other animal. Take a picture of your new pet. Hand it in with your lab.

Station 2: Playing with Play Dough

Take a piece of Play Dough and mold it into a kitten, dinosaur or some other animal. Take a picture of your new pet. Hand it in with your lab.

Station 3: Sodium Polyacrylate

Sodium polyacrylate is used in diapers and absorbs water. Add a sample of the powder to a small cup (0.2 grams) and slowly add water to it until it saturates. Record your observations. You may touch and handle what forms.

Station 5: Carbon Snake

Put a small drop of sulfuric acid on sugar.

Station 6: Origami/Plane Building.

Leave out an origami book or have students build a plane/shape.

Build a paper airplane…

Station 7: Color Change

5mL Silver Nitrate and add a sodium chloride solution. Or Potassium iodide and lead nitrate

Station 8: Formation of a Precipitate.

5mL Silver Nitrate and add a potassium chromate

Station 2: Its Getting Cold up in Here

Take a piece of ice and put it down a group member’s shirt. Let the ice melt. Remember to do this in a safe fashion, there are chemicals and open fire in this lab. Record your observations.

Station 6: Eggzactly Like that

Put a drop of oil on a hot plate. Cook an egg. Flip it without breaking the yolk (or you lose points). Record your observations.

Station 7: Sparkler

Light a sparkler and observe what haopens.

Station 8: Combusting Steel Wool

4Fe+ 3O2---> 2Fe2O3

Combustion of steel wool

2H2 + O2 2H2O

Formation of water

2H2O  2H2 + O2

Electrolysis of water

Teacher Guide: