Making fizzy blocks with baking soda is one of the most entertaining and educational activities I've done with kids recently. I love how simple the ingredients are—just baking soda, water, gelatin to firm up the blocks, and food coloring to make them vibrant and appealing. The best part is watching the reaction when vinegar is poured over the frozen blocks, creating that satisfying fizz that kids absolutely adore. I found adding the gelatin optional but helpful if you want the blocks to hold their shape better once they’re frozen. For added excitement, hiding small waterproof toys inside before freezing was a hit—kids loved the surprise element as the fizz helped reveal their 'hidden treasures.' When doing this activity, safety is always a priority. Though the ingredients are taste-safe, I always supervise toddlers to avoid any accidental ingestion of the vinegar or the mixture. To manage the fizzy mess, using a large tray underneath is a smart way to keep cleanup easy. If you don’t want to freeze the blocks, an alternative is mixing baking soda, a bit of cornstarch, and water, then letting the mixture air dry for a few hours until firm. This no-freeze method produces moldable blocks that also fizz when vinegar is applied but can be less messy. Overall, this activity is fantastic for sensory play, helping children explore cause-and-effect, colors, textures, and basic chemistry concepts while having loads of fun. It’s ideal for rainy days or as a creative project during learning-at-home sessions.