Skip to Main Content / Passer au contenu

Resource Library

Resource Library  |  Additional Inquiries  |  Grades 4 to 6, Grades 7 to 9

How much water is in a tomato?

Above Image: Tomatos with water droplets © harneshkp,


Students will conduct a basic guided inquiry to determine the mass of water in a tomato. Students will consider the value of using dried food in the context of meeting human needs in space and as a food preservation technique.

Inquiry Skill Development

  • Following a basic method to dry fruit
  • Making predictions
  • Collecting and measuring mass data (using a beam balance)
  • Using collected mass data to calculate the mass of water in a tomato
  • Decision-making from acquired learning

Concept Development

  • To make connections about the potential role and value of tomatoes for long term space mission
  • To understand that drying food is useful form of food preservation

Prior Knowledge and Skills

  • Understanding of basic human needs
  • Skills of operating a beam balance

Success Criteria

  • Students engage in discussions
  • Students demonstrate correct use of a beam balance
  • Students prepare and submit a final Inquiry Summary
  • Students collaborate to generate and present a Pros & Cons Organizer

Suggested Timing

    Minds On

    • 15-20 minutes of discussion, reading and/or video viewing
    • Background reading may be done outside of class time


    • 30 – 40 minutes class time to weigh and prepare tomatoes with students
    • 6-12 hours to dehydrate tomatoes (outside of class time)
    • 30 -40 minutes class time to weigh dried tomatoes and calculate mass


    • 15-20 minutes class time to discuss and complete a Pros and Cons Organizer


  • Space Foods (Tomatosphere™ backgrounder) - 1 per student

  • Human Needs in Space (Tomatosphere™ backgrounder) - 1 per student (Optional)

  • BLM 1: Inquiry Summary - How much water is in a tomato? – 1 per group doc pdf

  • BLM 2: Pros & Cons Organizer – Using Dehydrated Foods in Space – 1 per group doc pdf

  • 6 – 8 tomatoes: from Tomatosphere™ plants or other small tomatoes (about 3 – 5 cm diameter) - 1 tomato per group

  • Oven-proof tray

  • Access to an oven at 70-100°C (150-200 °F) for 6 – 12 hours or a crock-pot for 12-16 hours over 2 days

  • Paring knives (one per group)

  • Access to a triple beam balance

  • Life in Space: Food! - BIS (Video on Tomatosphere™)

  • Chris' Kitchen Part Deux: Space Spinach Strikes Back - CSA (Video on Tomatosphere™)

Tips for Success

  • Organizing working partners and/or discussion groups prior to the lesson is recommended.
  • Background reading and/or video viewing may be assigned prior to class in preparation for the inquiry in-class discussions.


Exploring space foods and eating in space

Step 1

Have students read the Space Foods backgrounder as a pre-class or in-class reading assignment.

Step 2

Conduct a class discussion to access student prior knowledge about how astronauts satisfy their basic need for food while living in space.

Questions to initiate and guide the discussion may include:

  • What do astronauts eat in space? What types of food are available for astronauts?
  • How does food get to the astronauts on a space mission?
  • What methods are used to keep the food fresh and safe?
  • How is food prepared in space?
  • Is the food as nutritious as the food we eat on Earth?

Step 3

Follow the discussion by viewing Life in Space: Food! (Video on Tomatosphere™). In this video, Canadian astronaut Robert Thirsk and Belgian astronaut Frank De Winne discuss the different types of foods available on the International Space Station (ISS) during their 2009 mission.


Conduct the Inquiry: How much water is in a tomato? (Dehydrating Tomatoes)

Step 1

Divide the class into working groups of 3-4 students.

Step 2

Provide students with BLM 1: Inquiry Summary - How much water is in a tomato? Using this page as a guide, students should develop an inquiry question, make a prediction/hypothesis regarding the question, and justify their hypothesis.

Scaffolding Questions:

  • How much water do you think there is in the tomato you have been given?
  • What will the tomato look like after the dehydration process?
  • What remains of the tomato will be evident at the end of the dehydration process?
  • Will the percentage of water be the same for all the tomatoes that are dehydrated?

Step 3

Supply each group with a whole tomato. Ensure that groups in rotation have access to a paring knife, triple beam balance and oven-proof tray.

Step 4

Have students remove the stem and core from the tomato. See Figure 1.

Note: If your class has tomatoes from both of the Tomatosphere™ seed groups (e.g., groups G and H), they can compare the water content of the two groups and write an appropriate testable question. Monitor students for safe use of the paring knife as they are cutting the tomatoes.

Step 5

Instruct students to measure the mass of the tomato using the balance, and then record this information on BLM1.

Step 6a (Oven Drying Option)

Note: For student safety, the educator should perform all tasks involving the oven. A microwave oven is not suitable for drying tomatoes because it will not provide the essential continuous, moderate heat and air circulation required.

To prepare the tomatoes for oven dehydrating, have students:

  1. Slice the tomatoes in half (horizontally)
  2. Place the pieces on a rack on an oven-proof tray.
  3. Label the tomatoes using parchment paper and pencil so that each group can identify their own (e.g., Group A, B, C, etc.). Alternately, place all of each type of Tomatosphere™ tomatoes on separate trays (e.g., All Type G tomatoes on one tray and all Type H tomatoes on another tray). See Figure 2a.
  4. Place the tray of tomatoes in a 70-100°C (150-200 °F) oven for 6-12 hours. Leave the oven door slightly open to allow the moist, hot air to escape. The total time to dehydrate the tomatoes will depend on the temperature of the oven, size of the tomatoes and water content in the tomatoes. See Figure 2b.

Step 6b (Crock-pot Drying Option)

Have students prepare the tomatoes for crock-pot drying by:

  1. Slicing the tomatoes in half (horizontally)
  2. Placing one piece of crumpled tinfoil in the bottom of the crock-pot as a liner
  3. Placing the tomatoes directly on a second sheet of tin foil, on top of the liner foil (See Figure 3)
  4. Note: The purpose of the extra layer of foil in the crock-pot is to prevent the tomatoes from scorching due to being too close to the hot ceramic surface of the crock-pot. Advise students not to touch the ceramic parts or lid of the crock-pot. Limit the number of students who are observing the tomatoes in the pot at any one time.

  5. Turn the crock-pot to high. Keep the lid on the pot slightly ajar so that the moist, hot air can escape.
  6. The tomatoes should dry out in 12-16 hours over 2 days. The crock-pot can be turned off overnight and the drying process resumed the next day. This drying method is easy to conduct in the classroom and allows the students to observe the drying process. Ensure the crock-pot is placed in a safe area, where it cannot be knocked over or pose a tripping hazard.

Step 7

When the tomatoes appear dry, remove them from the oven or crock-pot. Dried fruits should be leathery and pliable, but not sticky when cool.

Step 8

Have students measure and record the mass of the dried tomato and make observations, using BLM1 as a guide. Have students compare the mass of the dried tomato with the original mass of the tomato.

Step 9

Using the equation provided on BLM1, have students calculate the percentage of tomato mass that was lost during dehydration.


Exploring the Pros and Cons of Using Dehydrated Foods

Students will consolidate their understanding of the application and value of drying food for extended space missions using a Pros and Cons Organizer strategy.

Step 1

Have students watch the video Chris' Kitchen Part Deux: Space Spinach Strikes Back - CSA (Video on Tomatosphere™). Chris Hadfield demonstrates how spinach is rehydrated in preparation for a meal on the ISS.

Step 2

Organize students into table groups and provide each group with a copy of BLM 2: Pros & Cons Organizer – Using Dehydrated Foods in Space Missions organizer template.

Step 3

Have student groups discuss the pros and cons of using dehydrated foods for space missions for 10 – 15 minutes and organize their ideas using the organizer provided.

Step 4

You may wish to have the groups present their summaries to the rest of the class or conduct a full class discussion to summarize the discussions at the table groups.


  • Let the class taste the dried tomatoes once the inquiry in completed. Always check for potential allergies prior to tasting.
  • Discuss the potential uses of dried tomatoes
  • Explore the use of dried foods in Indigenous cultures (e.g. pemmican is a combination of dried meat, fat and berries)
  • Have the class use the dried tomatoes in a simple recipe such as pasta sauce.
  • Discuss other types of common dried fruits and learn how they are dried (e.g., grapes to make raisins, plums to make prunes, fruit leather, etc.)

Additional Information

The Tomatosphere™ team is interested in collecting exemplars and photos of our learning strategies in action. Please consider sharing with us at: