Our weekends are generally busy, and December weekends are even busier. In addition, Anna was a little cranky after being cooped up inside for a few days due to a bad weather. She went on Saturday to a birthday party for her classmate and brought back a helium-filled balloon. We talked a lot about why this balloon floats to the ceiling while her other balloons don’t do that. I tried to explain that this balloon has a special gas inside that is lighter than air. This causes balloon to lift up. Anna asked an interesting question – whether the hot air balloons also have this special gas. I tried to explain to her that no, it’s because they have hot air that is lighter than cold air, but it was difficult for her to understand, since I was not willing to get down to molecules and density lecture. Instead we entertained ourselves tying different items to the string of our balloon and seeing if it can lift them. We tried about 5 different things before we found something that would fly – a 2x2 lego block. The block made the balloon float in mid-air to Anna’s great delight. She played for good 30 minutes with it and learned a thing or two about lifting power in process.
Check out other science experiments at Science Sunday.