1 class periods of 45 minutes each
Small Groups
Five powders and five tests are provided for students to explore chemical and physical properties, changes, and reactions.
For the Student: (Groups of 5)
NOTE: Cafeteria trays or ice cream buckets provide an excellent way of passing out complete lab setups to each group.
A physical change occurs when the appearance of matter changes, but composition of the matter does not change. Changes in size, shape, color, odor, hardness, or in state such as gas, liquid, or solid are all considered physical changes.
A chemical change occurs when new kinds of matter are formed. The composition of the matter changes and the new kinds of matter have different properties from the old matter. Evidence of a chemical change may include production or use of energy such as heat or light, the new production of a gas or solid, or a change in color.
The five mystery powders in this activity have different physical properties, even though they are all white. Also, they will have different chemical reactions. Some will not react at all with the substance, only creating a physical change (wetting). Others will produce obvious chemical reactions.
The following changes and reactions can be expected in this activity:
1. Make observations.
2. Collect, record analyze data.
3. Seek and weigh evidence.
4. Solve problems using scientific principles.
5. Draw inferences.
Step 1. Divide the students into groups of 5. Explain that two observations will be made in these experiments.
a. Physical properties
b. Physical changes and chemical reactions.
Step 2. Each group should have a copy of the directions and the recording sheet. [See Mystery Powders Lab Directions and Recording Sheet attached below.]Before giving students directions, remind them about care in experimenting. Never taste unknown substances .
Step 3. After the investigation, discuss with the class their observations in the two areas:
a. Physical properties
b. Physical changes and chemical reactions.
Step 4. After group comparison of results, provide each group with a mystery sample and see if they can identify it.
Step four may be used as an assessment.
Show the children sugar and Kool-Aid. Instruct them to describe the physical properties they observe. Mix the two. Ask them to identify it as a physical or chemical change. Instruct them to justify their answer. Show students vinegar and baking soda. Instruct them to describe the physical properties. Mix the two. Tell them to identify the result as a physical or chemical change. Instruct them to justify their answer.