Lessons
Osmosis and Diffusion
Guiding Questions
- How do cell structures differentiate between osmosis and diffusion?
- How do organisms interact with surroundings to obtain matter and energy?
Students will pair up and chart their existing knowledge of cell structures and functions. They will join with another team to compare and contrasts their statements.
Many lessons are available in the public domain for teaching osmosis and diffusion. The most popular ones are the “eggsperiment”, and the gummy bears demonstration. Both utilize easy props for students to grasp the concepts of swelling, and shrinking (experienced by the egg or gummy bear) occurring when solutions of water, and material move through a semipermeable membrane.
One of the demonstrations involves potatoes. The demonstration is relatively inexpensive, and can be done at home. It involves a potato cut in half with each half carefully placed in to a separate container filled with water. The students are asked to label both containers - one as A, the other one B. The container marked A contains plain water. The container marked B is a solution with salt added to it. The size of the containers will determine how much salt needs to be added (usually two tablespoons are enough). Students will be asked to write their hypothesis in their notebooks. Students will come back either at the end of the day or the next morning and observe the potatoes. The potato in plain water might be a little colored, and will be a little dense. The potato in salt water will turn brown and shrivel. Students will then note their findings and see if their hypothesis matched their findings. An extension would be to come up with other situations in which osmosis and diffusion could be witnessed in a real life setting. An assessment could be the team of two drawing, and labeling containers depicting osmosis and diffusion reactions and then write their conclusion based on their drawings citing evidence to support their findings.
Dehydration
Guided Questions
- How do structure and function within a system function contribute to a positive environment?
- How do structure and function within a system potentially harm its’ well being?
The students will pair up and brainstorm what dehydration looks like, feels like, tastes like, and smells like – I added that category because bad breath is a frequent indicator of dehydration. In doing so they will have a foundation for an inquiry research project. They will develop and base their questions on materials gained from web searches, and library usage. Posters will be constructed on material and information obtained from their endeavors. The student are going to use the posters to generate “public service announcements” and visit classrooms on campus to deliver their message or proper hydration and the ill effects of dehydration.
There is also an excellent website with interactive available. Go to www.nasa.gov and type in hydration station. This site has a free access rating for material and lessons.
Design Challenge
Guided Questions
- How might someone acquire clean water from foreign surroundings?
- How might someone be able to differentiate various water samples using pH strips?
Constraints
The design challenge begins with students individually researching the properties of drinking water, coming up with their own definition for it. They need to use their working knowledge of pH levels from prior lessons to test and decide the pH of water they would drink. They will also have some samples of water to be able to test pH levels and record the data. Students also will use technology to find various filtering materials – cheesecloth, coffee filters, charcoal etc. When finished they will be assigned a team, given a challenge packet with instructions, rubrics and specifications.
Students will be assigned in teams of 3-4 depending on class size. I use heterogeneous group settings, pairing below basic students with basic and proficient ones. The students are asked to research first, design a prototype following set guidelines, and then submit for approval.
When working in a design challenge where there are tools involved, I will take a class period to go over safety mechanics with the class. They are instructed safety is the first priority, and accidents rarely are accidents due to students fooling around. After the safety lesson they are given a short quiz to make sure they understood the material.
I base my constraints on tool usage, materials supplied, materials they bring from home, and time allotments – usually 7-10 days. Design challenges are used as culminating events to the concepts I am teaching.
Students will choose to either devise rain gutters to trap water and storage units to keep the water available to use at a later date, or invent water-filtering apparatuses they can utilize at home or abroad. They will research water websites looking for information about obtaining and testing materials that would achieve their goal. In addition they will be required to search engineering sites for ideas on how to construct a sustainable prototypes. In both challenges STEM principles and standards will be taught.
An extremely well written lesson(s) available now are obtained from the following website: www.jpl.nasa.gov/edu concerning astronauts and their ability to recycle potable water. I will probably use some of its’ information in my own design challenge.
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