September 30th

Today we did our very first experiment involving chemical and physical changes! How exciting! :)

But first of all, if you can recall from the last class, what separates a chemical change from a physical one?

A chemical change is a change in the chemical composition of a substance. It cannot be undone, and new substances are created. A physical change, on the other hand, is a change in the physical state of a substance. It's reversible and no new substances are formed.



Yum! A rotting apple is a chemical change, as the oxygen reacts with the apple to produce something new. A melting
ice cube is a physical change because it is reversible and nothing new is created.



Experiment 2C: Chemical and Physical Change

Materials:

• four of the smallest test tubes available
• a test tube rack
• four medicine droppers
• a glass square
• safety goggles
• four samples of unidentified substances, which each went into a different test tube

Procedure:

1. First, we put on our safety goggles (safety is first, after all!).
2. Next, we placed each test tube into a hole in the test tube rack, calling them A, B, C, and D.
3. Ms. Chen placed a different kind of substance in each test tube, filling them about a third of the way.
4. Next, we drew a grid (below) the size of the glass square on a white sheet of paper.
   

   	A	B	C	D
   A
   B
   C
   D

   
   
5. We placed the clear glass square on the grid, lining it up so that the cells matched the holes in the glass. This made it easier for us to see which outcome was which when we were combining the solutions.
6. 
   
   The fun part! Taking the medicine dropper, we combined the solutions as shown in the white cells of the grid: AB, AC, AD, BC, BD, and CD.
7. 
   
   We recorded our results on a separate sheet of paper, on a grid that looked exactly like the one above. If there were no changes to the mixture, we wrote that down as well.
8. 
   
   Afterwards, we cleaned up (thoroughly, of course), and wrote our write-up on the results of the experiment.

The results:

In all, but one of the mixtures, chemical changes occurred. These ranged from colour changes (one mixture turned bright blue, another one canary yellow, and a third combination was a faint green), to fizzling (small bubbles popped up in the mixture, to solidifying (one mixture hardened, turning a milky white colour).

We were able to complete our objective (recording some characteristics of chemical changes), by witnessing firsthand the results of chemical combinations! :)

Extras:

 

^ Here's a fun and lively drink you can offer to your friends the next time you have guests over!

...don't.

Homework:

• 
  
  Lab 2C write-ups are due Friday
• 
  
  Chapter 1 + 2 test is on October 21st

See you guys soon!