Level: Grade 7
Content: Diversity of Materials in the Environment: Substances & Mixtures
1) Distinguish substances from mixtures.
2) Recognize that substances have unique set of properties.
This video shows changes that can happen when samples are subjected to heat. The laboratory apparatus that were used are watch glass, wire mesh (without asbestos), tripod, alcohol lamp and match, as shown in the image on the right.
Throughout the video, the students will try to answer the question,
Are Sample A and Sample B the same?
They have to support their answers with the observations they have noted as they watch the video. Below are some tips on how to guide the students in doing so.
1) The video may be paused at 00:02. Ask the students to take down notes on the appearance of the two samples. The appearance may be described in terms of the color, phase or state (solid, liquid or gas) and the sample size. You may ask the students if these samples are the same and let them elaborate their answers. Accept and note any answer. Put them in suspense as you continue to play the video.
2) At 00:16, prompt the students that the samples are being heated. Also, tell them to carefully observe what happens. Let them note their observations. They can also note the time at which they start to see changes.
3) At 00:38, some observable changes start to happen. Wait for the students to notice it by themselves. If students seem to be unresponsive, you may prompt them by telling that observable changes are already starting to happen. You may need to pause the video so the students can spot it. Ask the students to describe and note these changes. At 01:00, observable changes are more evident. The students should note how these observable changes happen for the two samples. Are the changes that are happening with the two samples the same?
4) You may pause the video at 1:16 and let the students note and describe the changes that happened with the two samples. What can they say now about these two samples? At this point, the students must have inferred that these two samples are different by their melting behavior. In fact, one is a substance and the other one is a mixture. From their descriptions of the melting behavior of these samples, the class may draw a definition of a substance and a mixture. You may further the discussion to other properties that may distinguish a substance from a mixture.
Watch the full video below.
The video may be downloaded upon sending a request e-mail to firstname.lastname@example.org. This video is best played using a VLC player.