Chemistry Unit- Lesson 7 and 8

Lesson 7:

Chemical and Physical Changes


We started by defining what a chemical change and a physical change is. Then they came up with some examples of each type. I also told them some of the ways to tell if a chemical change has occurred:

* a precipitate (I used the word solid for them) forms
* fizzing/bubbling
* a color change
*odor, heat or light is given off


Then we moved on to the experiment:

This was mostly observation. In the balance we set up foil, with clay (as a holder) and a candle and balanced it using other objects. We talked about the physical properties of the objects. Then we lit the candle and they talked about what they saw- the size of the candle changing, the wax melting to liquid then hardening back to solid. The smell in the smoke as the wick burned. And other chemical and physical changes the objects were undergoing.

Lesson 8:

Question: Did a physical or chemical change occur?

Hypothesis:
R: physical
C: chemical

Procedure:
Mix 3/4 cup of warm water, 1 cup glue and a few drops of food coloring in a bowl.
In a cup mix 1/2 cup warm water and 2 tsp borax.
While stirring slowly pour the borax solution into the glue solution.

Results:

(a solid forms!)

Conclusions:

A chemical change occured...

And it's a fun change too!