A study of Change: a laboratory Investigation Vocabulary and Concepts
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A Study of Change: A Laboratory Investigation
Vocabulary and Concepts
We have been studying physical and chemical changes. In a physical change, the substances present remain the same but change physical state. They are often easy to reverse. In chemical changes, a new substance is made and many times, these are irreversible changes.
In both physical and chemical changes, energy can be released or absorbed from the surroundings. If energy is absorbed from the surroundings, this is called endothermic, where endo means in and therm means energy. If energy is released to the surroundings, this is called exothermic, where exo means out. In a physical change, we call it an endothermic or exothermic process because it is not a reaction but a change of physical state. In a chemical change, we call it an endothermic or exothermic reaction because new substances are made.
In this lab we will prepare two experiments: we will make rock candy and we will fix something rusty.
Two 500 mL cups
1 clean jar without a lid
About 500 mL water
About 1000 mL sugar
Pot holder (to keep your hand safe)
Two skewers (see image)
One small piece of rusty metal (coin, nail)
200 mL vinegar (lemon juice)
Rock Candy Method
Make sure your jar is clean and dry
Put a pot on the stove and add 500 mL of clean drinking water
Turn on the heat and add 500 mL of sugar, stir until all dissolved
DANGER: DO NOT LET THE WATER BOIL!!! Keep the temperature low
Add another 500 mL of sugar, stir until dissolved
If it stops dissolving, do not add any more sugar. Otherwise, add a small amount of sugar and let it dissolve, then add a little more,...repeat until no more will dissolve.
Let the pot sit on the stove warm for about 5 min, not boiling. Then, turn off the heat.
DANGER: LET HOT LIQUID COOL FOR AT LEAST 15 MINUTES.
Test and set up your jar and skewer system. Place one skewer across the jar and one skewer in the middle of the jar. Using a piece of tape or a rubber band, attach the vertical skewer to the horizontal skewer. Place the horizontal skewer across the top of the jar and re-adjust the height so the vertical skewer touches the bottom of the jar.
Remove the skewer system from the jar
DANGER: POTENTIAL FOR BROKEN GLASS: Put the jar into the sink and slowly pour the cooled sugar water into the jar (should be warm but not hot!).
Dip the vertical skewer into the liquid, remove it, roll it in some solid sugar, then insert it back into the jar and skewer system
Cover this with a piece of plastic wrap that has small holes punched in it. You want things to get out but not in
Do not refrigerate. Put on the counter and record changes daily. Photos are useful too.
B. Rusty Metal Method
DANGER: DO NOT SPLASH ONTO SKIN OR INTO EYES; IF SPLASHING OCCURS, FLUSH SKIN AND EYES WITH LOTS OF COOL WATER
Into a clean 500 mL cup, pour 200 mL of vinegar
Take a photo of your rusty metal
Place your rusty metal into the vinegar
Note any changes you see
Let the rusty metal sit in the vinegar solution over several days, making as many notes as possible. Note the time and date each observation was made. It is useful to take photos.
When finished with your experiment, pour your vinegar down the drain and flush the drain with cool water for about 2 min.
Dry off your rusty metal piece and take a photo as evidence.
Image: Day 1 Jar and Skewer Set Up
Image: Day 2
Image 1 Piece of Rusty Metal
Image 2 Rusty Metal Day 1
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