Have you ever heard of a diver talking about ‘feeling pressure’ when they’re underwater? This is because water is much denser than air. A volume of water 10 metres thick applies the same amount of pressure as the entire Earth’s atmosphere (which is nearly 130km thick!). So, when a diver descends 20m underwater, they would experience the same pressure as two lots of Earth’s atmosphere pushing down on them. However, you don’t have to be a diver to see how depth affects water pressure. Just by using a recycled plastic bottle, you can experience it at home with this simple activity.
Step 1: Ensure your bottle is empty and safely remove any labels.
Step 2: Use your ruler to measure 7cm from the bottom of the bottle. Make a line with your marker.
Step 3: Now measure 20cm from the bottom of the bottle and add another line.
Step 4: Ask an adult to poke the nail or tack into each of the lines you’ve made. You only need one hole on each line.
Step 5: Cover up the two holes with tape.
Step 6: Fill up the bottle with water and secure the lid.
Step 7: Stand the bottle near the side of a sink, with the holes pointing towards it.
Step 8: Remove the tape and see what happens! Record your findings in the boxes below.
Now have a go at answering our questions: