Keeping the Harvest

Learning Guide

A simple guide to lead you through the kickoff, the core challenge, and everything in between.

Mai’s Tips

1. Safety first: A grown-up does the slicing, and nobody tastes the samples. Once a sample looks fuzzy or smells bad, do not touch or sniff it. Put it in a bag and throw it away with the grown-up.
2. Patience is key: The biggest changes take about 3 days, which is why there is a Day 3 check-in. Observing over time is a core part of real science. Don't rush to conclusions on Day 1.
3. Microorganisms misconception: Children often think food just 'gets old.' The key nuance to convey is that invisible living things are eating the food. If they struggle, use the analogy of tiny, tiny creatures at a buffet.
4. Simplify the 'why': If the concept of water removal isn't landing, simplify to 'microorganisms get thirsty and can't grow without water.' For salt, say 'salt sucks the water right out of the food, making it too dry for those thirsty little guys.'
5. Mold alert: The plain cucumber and the sealed apple may grow mold. This is part of the learning! Mold is a type of microorganism that spoils food.

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1Introduction: The Winter Challenge 5 min

• Begin by setting the scene for Thanksgiving long ago, when refrigerators didn't exist. Ask the central question of the Spark and let your child brainstorm freely. There are no wrong answers at this stage – just encourage creative thinking.

Know Before You Teach

• Good to know: Thanksgiving celebrates harvest and gratitude, often with historical connections to early American settlers and Native Americans.
• Before modern refrigeration, food preservation was essential for survival through winter.
• The Wampanoag dried their corn and beans to eat in winter, and kept some other foods by drying or smoking them.
• If they ask: Did they have refrigerators back then? No, refrigerators were invented much later. People had to find other ways to keep food from spoiling.
• It's working when: Child offering varied ideas, even if not fully correct (e.g., 'keep it cold,' 'put it in a cellar').
• If they're stuck: Suggest thinking about how nature might keep things fresh, like when leaves dry up.
• Easier: Focus on just one food item they know (like berries) and ask how their grandparents might have kept it for a long time.

• Harder: Ask them to think about different types of food (meat, fruit, vegetables) and if they'd need different methods.

Done when: Student has shared at least one idea about how food might have been kept from spoiling.

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2Explore & Plan: Our Food Preservation Test 8 min

• Explain that you will test two old ways to keep food: salting and drying. Each one gets a 'control,' a sample you leave alone so you can compare. The plain cucumber is the control for the salted cucumber. The apple ring sealed in a bag is the control for the drying apple. Ask your child to predict what will happen to all four, then show them the experiment log.

Know Before You Teach

• Good to know: Salting draws moisture out of food, making it less hospitable for spoilage organisms.
• Drying removes water, which is essential for microbial growth.
• A control group in an experiment is crucial for comparison to see if the tested variable (salt, drying) has an effect.
• Key words: Control: In an experiment, the control is the part that you don't change or treat, so you can compare it to the parts you do change.
• It's working when: Child making clear, distinct predictions for each sample (e.g., 'salted will get wrinkly,' 'plain will get yucky').
• If they're stuck: Ask them to describe what happens to food they leave out on the counter for a few days.
• Easier: Focus only on predicting what the salted cucumber will look like, using a simpler visual comparison (e.g., 'like a prune').

• Harder: Ask them to predict why each change will happen, linking it to water or other factors.

Done when: Student has made a prediction for each of the four samples.

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3Discussion: The Science of Spoilage 6 min

• This is where you explain the core concepts. Start by defining what causes food to spoil (microorganisms) and what they need to survive (water). Then connect this to how salting and drying remove or make water unavailable. Use simple language and ask guiding questions.

Know Before You Teach

• Good to know: These microorganisms require water to grow, reproduce and break down food.
• If they ask: Can I see microorganisms? No, they're too tiny to see with just your eyes! You'd need a special microscope to see them, but they are all around us and on our food.
• Key words: Microorganisms: Tiny living things, like bacteria and mold, that are too small to see without a microscope.
• Key words: Spoilage: When food goes bad, often because microorganisms are growing on it, making it unsafe or unpleasant to eat.
• Key words: Dehydration: The process of removing water from something, like drying fruit.
• It's working when: Child making the connection between water, microorganisms and spoilage, even if simple.
• If they're stuck: Use the analogy of a plant needing water to grow; if it doesn't get water, it shrivels and dies. Microorganisms are similar.

• Easier: Focus only on the idea that 'thirsty tiny bugs' can't grow without water, without naming 'microorganisms'.
• Harder: Ask them to think about other ways we keep food fresh in the fridge or freezer, and how that might work differently.

Done when: Student can explain in their own words that food spoils due to microorganisms and that drying/salting prevent this by removing water.

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4Activity: Setting Up Our Experiment 9 min

• Help your child set up the four samples. A grown-up does the slicing. Label each sample clearly. Then help them make their Day 1 notes in the experiment log, using what they can see and feel.

Know Before You Teach

• Good to know: Careful observation here means looking and feeling. Nobody tastes the samples.
• Consistent recording helps track changes accurately over time.
• If they ask: How much salt should I put on? Put enough salt on so that the entire top surface is covered, like a light dusting of snow. We want to really see the salt's effect.
• It's working when: Child carefully applying salt or arranging the apple, and making detailed initial observations beyond just 'good'.
• If they're stuck: If they're unsure what to write, ask: 'What color is it? Is it shiny or dull? Does it feel firm or soft?'
• Easier: The grown-up slices, salts and seals. Your child places the samples and draws what they see.
• Harder: Ask the child to consider where the best place in the house would be to dry the apple, and why (e.g., sunny window, low humidity).

Done when: All four samples are set up and labeled, and Day 1 notes are in the experiment log.

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5Summary: The Harvest's Secrets Revealed 2 min

• Explain that the samples need a few days to change, so the experiment keeps going after today. Talk about what they expect each sample to look like, and connect it to families keeping their harvest for winter.

  Day 3 check-in (worksheet page, about 5 minutes): on day 3, look at the samples, fill in day 3 of the log and compare with your predictions. Ask: 'What surprised you? Which method worked best, and why?' Once a sample looks fuzzy or smells bad, do not touch or sniff it. Put it in a bag and throw it away with the grown-up.

Know Before You Teach

• Good to know: The plain cucumber will likely show signs of spoilage (softening, discoloration, possibly mold) first.
• The salted cucumber will become limp and release water.
• The drying apple will shrink and turn leathery as it loses water.
• The sealed apple ring can't lose its water, so it stays soft and may start to spoil.
• If they ask: Why did the plain cucumber go bad so fast? Because it had all the water those tiny microorganisms needed to grow and start breaking it down! The salt and drying methods took that water away.
• It's working when: Child making connections between their observations and the explanations from Stage 3 (e.g., 'The salted one dried out, so the germs couldn't eat it').

• If they're stuck: Help them compare two specific items: 'Look at the salted cucumber and the plain cucumber. What's the biggest difference you see?'
• Easier: Focus on just one pair of samples (e.g., salted vs. plain cucumber) and what happened to them.
• Harder: Ask them to imagine another food item and predict which preservation method (salting or drying) might work best for it, and why.

Done when: Student can describe what they expect to see over the next few days and connect the experiment back to the main question of preserving food for winter.

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