Follow Our Step by Step Guide for Some Tasty Science Fun!
This classic experiment uses a simple cardboard box to harness the power of the sun to create a solar oven capable of melting some yummy chocolate, making it a fantastic introduction to renewable energy and a must-try experiment for sustainable STEM toys enthusiasts. Aim for clear skies and temperatures above 15°C.
Step 1: Gather Your Materials
Start by collecting all items to ensure a smooth build. If you are doing this experiment with young children, collect all the materials ahead of time as time spent searching for items can cause frustration in impatient kids.
- A clean shallow cardboard box (e.g., a medium pizza box, about 30-40cm square for easy handling).
- Aluminium foil (standard kitchen roll, enough to cover the interior).
- Cling film or clear plastic wrap (transparent to allow sunlight through).
- Black construction paper or card (A4 size or larger, to fit the box base).
- Tape (masking or duct tape for secure attachments).
- Scissors (child-safe if involving kids).
- A ruler or wooden stick (for propping the lid).
- Optional enhancements: A thermometer to measure heat, and treats like chocolate squares or marshmallows for testing.
Step 2: Prepare the Box Lid as a Reflector
- Open the box and focus on the lid first, which will act as a sunlight collector.
- Cut a square flap in the lid, leaving about 2-3cm border on three sides (like a window). Do not cut the fourth side—keep it attached as a hinge.
- Fold this flap upwards to create an opening that lets sunlight in.
- Cover the underside of this flap (the side facing inside when closed) completely with aluminium foil. Smooth it out and tape securely.
- Purpose: The foil reflects and directs sunlight into the box, maximising energy capture. This step demonstrates reflection in physics.
Step 3: Line the Box Interior for Heat Absorption
- Now, address the inside of the box to optimise heat retention.
- Cover the entire bottom and sides of the box with aluminium foil, shiny side up. Use tape to fix it in place without wrinkles.
- Place a sheet of black construction paper on the bottom, over the foil. Trim it to fit snugly.
- Purpose: The foil on the walls reflects any stray light towards the centre, while the black paper absorbs sunlight and converts it to heat. This illustrates absorption and heat transfer.
Step 4: Seal the Opening to Trap Heat
- Cover the square opening you cut in the lid with cling film or clear plastic wrap.
- Stretch it taut across the hole and tape it securely on all sides to create an airtight seal.
- Purpose: This acts like a greenhouse window, allowing sunlight to enter while trapping warm air inside. It prevents heat loss, showing the greenhouse effect in action—great for discussing climate science with primary school children.
Step 5: Prop the Lid for Optimal Sunlight Angle
- Use the ruler or stick to prop up the foil-covered flap at an angle (about 45-60 degrees, depending on the sun's position).
- Tape one end of the prop to the flap and the other to the box edge for stability.
- Adjust the angle to face the sun directly—track the sun's movement for best results during UK summer midday (11am-3pm).
Purpose: Angling maximises sunlight reflection into the box, enhancing efficiency. This step teaches basic engineering.
Step 6: Test and Observe the Oven in Action
- Place your treats (e.g., chocolate) on a plate on top of the black paper inside the box.
- Position the assembled oven in direct sunlight, away from shade or wind.
- Monitor: In 20-30 minutes on a warm day (20-25°C), the interior should heat to 80-100°C.
- You'll see the treats melt gradually, starting from the edges.
Safety Note: Supervise children; the box can get hot. Use oven mitts if needed.
What to Expect: Visible melting demonstrates solar power's potential, sparking interest in sustainable engineering tools for makers UK. Record temperatures with a thermometer for a data-driven twist, encouraging fun math games for primary school children.
Enjoy your melted chocolate!
Buy our downloadable colourful and engaging PDF version of this experiment HERE.
