STEM Activity: A Cranberry Investigation

Have you ever spotted cranberries in juice, dried fruit mixes, baked treats or on a holiday dinner table? Enjoyed for generations, these bright red berries are one of the few fruits native to North America.

In this STEM investigation, you'll explore a cranberry inside and out, test its fascinating properties and observe how it changes when heated.

What makes a cranberry unique? Try out two hands-on activities to investigate and find out!

Activity 1: Float and Dissect

Materials Needed:

• Bowl
• Fresh cranberries (small handful)
• Water (1 cup)
• Safe cutting tool

Safety Note: Adult supervision is recommended when using a safe cutting tool.

Step-by-Step Instructions:

1. Pour 1 cup of water into a bowl.
    
2. Place the cranberries in the water.
    
3. Observe what happens. Do the cranberries float or sink?
    
4. Remove one cranberry from the water.
    
5. Have an adult help cut the cranberry in half with a safe cutting tool.
    
6. Examine the inside of the cranberry. What do you notice? Can you spot any air pockets?

What Are We Discovering?

Did you know that fresh cranberries float in water? Scientists can investigate buoyancy by looking for clues in an object's structure. When you cut open a cranberry, you'll notice several small pockets inside the fruit. These chambers contain air, which helps make the cranberry less dense than water. This helps explain why cranberries float.

Cranberries grow on low vines in sandy bogs and wetlands. Every autumn, this floating characteristic is especially useful during harvest. Many cranberry bogs are flooded, causing the berries to float to the surface where they can be gathered more easily.

Activity 2: Heat It Up!

Materials Needed:

• Fresh cranberries (a small handful)
• Water (1 cup)
• Saucepan
• Stirring spoon
• Stovetop (for heating the cranberries and water)

Safety Note: Adult supervision is required when using a stove or handling hot foods and cookware.

Step-by-Step Instructions:

1. Place the cranberries and 1 cup of water in a saucepan.
    
2. Place the saucepan on a stovetop. Heat the cranberries with adult supervision.
    
3. Watch and listen as the cranberries cook. What do you notice?
    
4. Stir occasionally.
    
5. Observe changes in the berries' shape, color and texture. What differences do you notice between the fresh cranberry and the heated cranberry?
    
6. Turn off the stovetop and remove the saucepan from the heat.

What Are We Discovering?

This activity demonstrates how heat can cause materials to change. You observed how a cranberry changes as it cooks, pops and transforms into the familiar cranberry sauce found on many holiday tables. As the water inside a cranberry gets hotter, it expands and creates pressure inside the fruit. Eventually, the outer layer of the cranberry can no longer contain that pressure and the cranberry bursts open. Did you hear a popping sound?

The firm cranberry you examined in the first activity becomes soft as its internal structure changes. The air-filled chambers collapse, the skin splits and the fruit begins to break apart. This investigation demonstrates how changes in structure can lead to changes in a material's properties. The same cranberry that floated in water can be transformed into a soft, thick sauce through the addition of heat. As cranberries cook, they release pectin, a natural substance found in plant cell walls. Pectin helps cranberry sauce become thick and gel-like instead of remaining watery.

National Inventors Hall of Fame Inductee Connection

Growing cranberries requires more than harvesting berries. Farmers must also protect their crops from pests and diseases. National Inventors Hall of Fame^® Inductee Pamela Marrone developed nature-based pest management solutions that help farmers grow healthier crops.

Having been interested in and inspired by nature since her childhood, Marrone became an entomologist and entrepreneur who has brought biological pest control products to farms around the world. Her work demonstrates how scientific observations can lead to innovations that support both agriculture and the environment.

Keep Exploring STEM

The next time you see cranberries featured in foods or kitchens, be sure to share your findings from this STEM exploration! Ready to explore more STEM through everyday foods and ingredients? Sign up to receive monthly emails with brand-new challenges and hands-on activities.