THE SOAP-PROPELLED BOAT – or how to brighten up bath-time What you’ll need: • Card • Scissors • A baking dish full of water (or you can do it in the bath at home – your call!) • Liquid detergent What to do: • Cut out a boat shape from the card. (Make it about 6cm long and 4cm wide) • Make a notch at the back of the boat. • Place the boat gently on the water in the dish. • Pour a little detergent into the notch in the end of the boat. Your boat should zip across the water… What's happening? Water molecules are strongly attracted to each other and stick close together, especially on the surface. This creates a strong but flexible "skin" on the water's surface that we call surface tension. Adding soap disrupts the arrangement of the water molecules and breaks the skin, making the boat go forward. Go back