Observation & Inference

LAB TASK #1

You have four powders: baking soda, cornstarch, powdered sugar, and plaster of paris. Your job is to figure out which one is which. You must make careful observations of each powder to try to determine its identity.

You may observe them in any of the following ways:

• What do they look like? (Try using a magnifying glass.)
• What do they feel like? (Pinch some between your fingers.)
• What do they smell like? (Be careful not to inhale them up your nose.)
• DO NOT TASTE THEM!

​

Setting Up:

Place a small amount of each powder (baking soda, powdered sugar, cornstarch, and plaster of paris) on a square of wax paper or in a weigh boat. It is important that you label the square as “Powder #1,” “Powder #2,”, “Powder #3,” and “Powder #4” and be consistent with the corresponding powders for all three parts of this lab.

Start:

Students record observations of each powder according to the suggestions on their lab worksheet. A magnifying glass is useful for doing a close observation of each powder.

Ask students to turn and talk to their partner and discuss what they think each powder might be.

LAB TASK #2

1. Take a small amount of each of the powders and place it in a small dish.
2. Add 3 drops of water to each powder.
3. Mix the liquid and the powder together and observe what happens.
4. Write your observations in your table.
5. Repeat steps 1–4 for vinegar and iodine.

​

Students will see that it is not enough to do a simple set of observations to make a complete inference. By mixing the powders with different liquids, students will be able to determine the identity of each powder by matching their observations with facts about the mixtures.

Setting Up:

Provide each group with three wax paper squares of each of the four powders (12 total). Again, it is important that powders are labeled and consistent with Part 1.

Each group should also get a small amount of each of the liquids, which can be provided in cups at each table. The liquids must be labeled.

Start:

Students should follow the procedures from their lab worksheet. They carefully record their observations in the chart. Tell them to be very specific and as accurate as possible with their descriptions. Most of their observations will be qualitative; however you can encourage quantitative observations such as the amount of time it takes for a reaction to occur.

LAB TASK #3

Use the table below to help you determine the identity of each of your mystery powders.

Use the sentence frames to make inferences.

Facts about powders and their reactions with liquids

​

Inference Sentence Frames

​

Students will use the fact chart to identify the mystery powders. By carefully comparing the observation chart with the facts, students can make inferences about the identity of their powders.

Students should use sentence frames at bottom of the page.

When finished, reveal the mystery powders to the class. Celebrate successful matches and reinforce the fact that careful quantitative and qualitative observations led to accurate inferences. Students will need to continue to make careful observations and accurately chart, graph, and record the data from these observations.

Pre-discussion Writing Prompts:

1. List two examples of qualitative observations that you made.
2. List an example of a quantitative observation that you made.
3. What observation helped you figure out which powder was baking soda?
4. Why did you have to do more than one kind of test to figure out which powder was which?

Students should use their observation charts from the Identifying Powders Lab as they think about the questions.

After students have written, ask them to share with a partner.

Discuss the previous questions as a whole class.

Some students may benefit from one or more of these sentence frames during the discussion.