# [2014] ofredtte7: Tropical Island - Puzzling Scenarios Project

In Glogpedia

Last updated 7 years ago

Discipline:
Science
Subject:
Experiments
8

Bouyancy- the upward force on an object exerted by surrounding fluid.Density- the measure of matter in a certain amount of volume.Viscosity- a liquid's resistance to flow (Honey is an example of a viscous liquid.Mass- The amount of matter that is in a shape.Volume- The measure of the amount of space an object takes up.

Question 1: Give your friend a scientific reason relating to density to explain why she floated better in the ocean.

It is much easier to float in saltwater for many reasons. The first is that saltwater is more viscous than fresh water, which means that the atoms are packed closer which slows descent. Another reson that it is easier to float in salt water are that humans are made up of 70% water, which makes them close to the density of water, almost in fact, 1g/ml but their density also has other variables, like if their lungs are full of air or not, their body mass index, and their weight or size. Salt water has a greater density than water, because the salt has dissolved in the water, it makes the densities closer. It makes the density closer because the mass is increasing and the volume remains constant, making the atoms more compact. As the density increases, the weight increases. When someone floats in salt water, they displace a certain amount of water. These shapes have the same volume, but won't have the same weight. If you weigh less then the liquid you displace, you will float, and vice versa. When densities are closer together, neutral buoyancy is the result. Nuetral bouyancy is the example of when the force of gravity is equal to the force of density. If not exactly the same, you will float easier but will not hover. The less dense you are, the more you will float and the less energy you will have to expell to stay above the water.

Layered Liquids

This diagram shows examples of hovering, floating, and sinking. Nuetral buoyancy is hovering, and an example of gravity and buoyancy being equal. Positive buoyancy is floating, an example of buoyancy acting as a greater force than gravity. Negative bouyancy is an example of sinking, and also an example of gravity acting as a greater force than density.

Question 2: Your friend finds a well on the island that provides fresh and salt water. How is this possible?

On the island, you're friend is looking for water and digs a well. In the well, she finds not only fresh water, but also salt water. An explanation to this is because the densities are different. If salt water is saturated meaning all of the salt has dissolved into the water, then when combined with fresh water which has a lower density, will seperate because their densities are not the same. Fresh water is more compact because its mass is greater as the salt has dissolved into the water. To represent this answer, we did an experiment to show exactly how the fresh and the salt water seperate. If your friend finds a well wih salt water and fresh water, it is because the density of the salt water is greater at 1.2g/ml and will sink while the fresh water which only has an average of 1g/ml, will layer itself on top. We show this by doing the salt water density lab, and dying the water/salt water different colors to make the layers obvious.

This diagram shows an example of our second question. It is a simple drawing of a well and as you can see, shows the layers at the bottom of the water table of salt and fresh water.

This is a picture of our experiment to represent our first question. It shows how in both waters, some objects with densities inbetween both liquid's densities can float in one fluid, or sink in another. For example, this egg must have a density between 1g/ml and1.2g/ml.

Egg in Salt Water vs.Fresh Water

Keywords

This diagram shows the atomic structure of solids, liquids, and gasses. Solids have atoms that are packed close and vibrating, liquids are flowing and are more free, and air has very few atoms in a given space, and have no definite volume and slip and slide everywhere.

This is the equaion for density. Density is the measurement of the amount of stuff (mass in this case) in a certain area (volume). This is one of the most important equations in this project and in other scenarios, can be manipulated to find volume or mass instead.

This is a picture of our second experiment, the layered liquids. The picture shows two liquids, each dyed a different color, have been poured in the same container. One liquid is normal water, and the other is saturated salt water. As you can see, the red fluid is on top of the blue, as it has a lower density. This helps show evidence to the answer for our second question, showing that salt and fresh water can both exist in the same container.

Tropical Island-Puzzling Scenarios projectBy Stephen and Owen

P5