Crusoe’s Science

Crusoe's Science

Robinson science3If you got stuck on an uninhabited island like Robinson Crusoe you will need to know how to get salt for cooking and drinking water for survival.
So, here you go:

What you need:Robinson science1
• large bowl
• short glass or cup
• tape
• plastic wrap
• small rock
• pitcher of water
• salt
• long spoon for stirring

What you do:
• Make saltwater by adding salt to fresh water.
• Stir the water until the salt dissolves.
• Pour about two inches of saltwater in a large bowl.
• Take an empty glass and put it in the bowl. The top of the glass should be shorter than the top of the bowl, but higher than the saltwater.
• Put plastic wrap over the top of the bowl. You may need to use tape to make sure the seal is tight.
• Put small rock right in the center of the plastic wrap, over the empty glass. That will weigh the plastic down and help you collect the water. Now you’ve made a solar still. It’s called a still because it distills, or purifies, water.
• Leave your still outside in the sun.
• Leave it alone for a few hours, or even a whole day. The longer you leave it out, the more water you’ll collect.
• When you’re ready to check your still, take the plastic wrap off and look at the water that’s collected in the cup. Do you think it’s salty or fresh?
• Taste it.

Robinson science2

Tip: Rays from the sun heat up the salty water in the bowl. When the water gets warm, it evaporates and becomes a gas. When the gas rises and hits the plastic wrap, it turns back into water droplets. Eventually, gravity makes the water droplets roll down the plastic wrap towards the rock. Then the water droplets slide off the plastic wrap into the glass. The salt doesn’t evaporate, so it gets left behind in the bowl. Water evaporates in the same way from lakes, rivers, and oceans. The water heats up, turns into a gas, and then condenses to fall back down as rain.

Magic Bottle

Magic bottle cover

What you need:magic bottle
• a bottle of water
• a needle

What you do:
• Put six small holes near the bottom  of the bottle, all around it.
• Give the bottle to your friend and ask him to have a drink.
• Watch what happens.

When the cap is on the bottle, the air pressure in the bottle is equal to the air pressure outside the bottle. Since the pressure is the same nothing comes out of the uncovered hole at first. When the cap is taken off, the water squirts out of the bottle. The water pressure in the bottle is greater than the air pressure on the out side of the bottle. The reason for this is because the weight of the water caused by gravity has a greater pressure then the air pressure outside of the bottle.

The weight of the water in the bottle causing pressure causes the water to shoot out of the lowest hole the farthest. This is because the height of more water above the hole has more weight and creates a greater pressure that the hole that is higher on the bottle.

Water Density

Water density cover

What you need:Water density
• Clear glass or Jumbo Test Tube
• Pipettes or droppers
• Sugar
• Measuring spoons
• Food coloring
• 4 small cups

What you do:
• Fill your cups with 1 cup of warm water and add food coloring to the water.
• Add 2 tablespoons of sugar to the 1st cup, 4 tablespoons to the 2nd cup, 6 tablespoons to the 3rd cup and 8 tablespoons to the last cup.
• Label each cup with the amount of sugar added.
• Stir the water until the sugar is dissolved.
• Start with the cup with the most sugar. Using a pipette, dropper or back of a spoon, begin adding the first layer of sugar water.
• After the first layer, things get challenging. Carefully drip the next dense layer onto the surface of the first. The best technique is to place the pipette right above the surface of the first layer and against the glass. Slowly drip the next color onto the first. This will take a lot of patience. Go slow.
• The colors will begin to mix at first and then your original color will start to show.
• Repeat with the next dense color and the least dense color until you have stacked all of the colors.

NB.: The more sugar you add to the water, the more sugar molecules will take over the space, making the water more dense. The cup containing the 5 tablespoons of sugar will be the most dense, the cup with 1 tablespoons will be least dense. That is why we layer them with the most dense liquid at the bottom and the least dense at the top.