Technology and engineering instruction teaches students to use their science knowledge, some technology, and the engineering design process to solve problems. Growing enough food is a problem for many people. Students might not be aware that it is possible to grow plants indoors without soil, if a water source is available.
Large print or tactile ruler or talking measuring tape
Plastic pipe*, 15 cm in diameter, about .6 meters or 2 feet in length
2 sheets of plastic*, approximately 5 mm thick, approximately 17 cm. square
Flexible tubing*, about one cm in diameter and 1.22 meters in length (about 4 feet)
2 Tubing adaptors with rubber washers and nuts
Small hose clamps
Hot glue gun and glue
Plastic screening* (fine holed), a square about 8cm by 8 cm
Plastic pail that will hold about 1 liter of water
Pieces of wood, one at least 60 cm long by 25 cm wide by 2cm thick to serve as a base for the unit and another one that will fit under the pail to elevate it.
Saws* (one to cut 6 cm hole and one to cut the boards)
pH testing kit
Sterilized garden sand
Funnel with a short, large opening
4 small potted plants
Talking Lab Quest and pH sensor
5 cc measuring cup
Plant food suitable for a hydroponics system
This project involves the use of tools so please follow all safety precautions. Remind students to ask for help when needed, and staff and students must always wear safety goggles.
Because tap water contains chlorine, measure one liter of water and it stand for 2 days to eliminate the chlorine. (Students can do this step in the preparation.)
Some parts of this activity involve using tools. If the students have not yet learned to use tools, staff will precut, or cut when needed, the following: (indicated in the materials list by an asterisk*)
Follow all safety precautions that accompany each tool!
These pieces need to be cut in advance:
The pieces of plastic sheeting
Pieces of wood
The pipe, both the length and the holes for the plants
The student will:
Tactually and visually examine a completed hydroponics system. What do you notice? How do these plants look compared to other plants you have examined?
Begin construction of a system by placing one sheet of the 5 mm thick sheet of plastic (precut*) on the tray.
Place the pipe (precut*) on end in the center of the plastic square. Trace around the bottom of the pipe with a contrasting colored marker or a tracing wheel. The tracing wheel will leave a tactile mark. Similarly mark the second sheet.
Place one of the marked sheets of plastic on a cork board or other non-slip surface. Measure up about 5 mm from the edge of the circle. Drill* a hole or use an awl to make a hole in the plastic sheet by inserting the awl through the plastic into the cork board. This hole will hold a tubing adaptor later in the construction process.
Ask for assistance to punch or drill a hole through the pail. The hole needs to be on the side of the pail about 20 mm from the bottom. This also will be used to hold a tubing adaptor.
Attach one tubing adaptor through the hole in the plastic pail and the other tubing adaptor through the hole in the plastic sheeting. Tighten the nuts that hold the adaptors in place.
On the onside of the plastic sheet with the adaptor, put hot glue in a circle around the adaptor.
Place the square of screening over the adaptor and press it against the wet glue. Let dry.
This screen will catch any loose sand from the system.
Stand the pipe, apply a circle of plastic glue to the end of the pipe then press the plastic sheet that does not have the adaptor onto the end onto the wet glue. Let dry.
When the end is dry, turn the pipe over so that the plastic sheeting with the adaptor facing out can be glued to the other end, following the same method as above. Use a ruler or another method to assure that the sheets are aligned so they will rest evenly on the table. Clamp if needed. Let dry.
Mark the location for your plant holes! Use a 6 cm hole saw to cut the holes.
Attach the flexible tubing to the planter and the pail using hose clamps to lock the tubing in place
Fill the planter with water, check for leaks and repair if needed. Remove the water.
Fill the planter about half full of sand carefully pouring the sand through the holes made for the plants. A funnel will help keep the sand from spilling. The amount of sand needed will vary.
Remove the plants from the pot. In a large bucket filled with water, rinse the soil off the roots of each plant. Dispose of this water outside where the water and dirt will be helpful. Place the plants into the planter. Place the planter on the large board.
With the pH sensor and Talking Lab Quest, test the pH of the water that was set aside in preparation for this activity. A reading of 6 to 7 is best for plant growth. If the reading id below 6 it is too acidic, add baking soda, less than 5 cc at a time until a pH approaching 7 is reached. If the pH is above 7, the water is too basic, add less than 5 cc of vinegar at a time to increase the acidity of the water and bring it to 7 or below. Retest after each addition.
Add plant food to the water in the amount specified on the package for growing plants hydroponically.
Place the smaller board on the board holding the planter. Place the pail on this board. Partially fill the pail with water until the water fills the planter.
When the planter is full, remove the board from under the pail and the extra water will drain back into the pail. Cover the pail to reduce evaporation. Add water/ plant food solution to the pail as needed.
Check daily to ensure that the sand remains moist. Keep a record of how much water needs to be added to the pail.
This activity was based on one found in Introduction to Technology, by Pierce and Karwatka, published by McGraw Hill Glencoe in 2005.
If all of this seems like too much work there are hydroponics systems for sale. https://www.hydrofarm.com/p/EMSYST is just one example. As usual the choice is either spending more time or spending more money to develop a system!
ETS1.A: Defining and Delimiting Engineering Problems
The more precisely a design task’s criteria and constraints can be defined, the more likely it is that the designed solution will be successful. Specification of constraints includes consideration of scientific principles and other relevant knowledge that are likely to limit possible solutions. (MS-ETS1-1)
ETS1.B: Developing Possible Solutions
A solution needs to be tested, and then modified on the basis of the test results, in order to improve it. (MS-ETS1-4)
There are systematic processes for evaluating solutions with respect to how well they meet the criteria and constraints of a problem. (MS-ETS1-2), (MS-ETS1-3)
Sometimes parts of different solutions can be combined to create a solution that is better than any of its predecessors. (MS-ETS1-3)
Models of all kinds are important for testing solutions. (MS-ETS1-4)