Anastasia's science portfolio

Density, convection, diffusion



How does it work?

Water has a density of 1.0. For example 1kg mass of water equates to 1000cm3 or 1 litre of water. The waters density is lower than the density of an egg,. As the egg was placed into the water it sunk to the bottom. This occured because the egg withheld a higher and denser overall mass and volume than the water. The density of an egg can be identified, although every egg has a slightly different mass and volume. On average it is estimated that the density of an egg is around 1.2 and that is why it sinks. This means that the density of an egg would be larger be than 1.0 (the density of water).

Later on in the experiment, 7 tablespoons of sugar were added into the water. Once it had been thoroughly mixed and dissolved into the water, the sugar, which has an extremely high density, ended up raising the density of the sugar/water solution. The overall density of the water and sugar together had a higher density than the egg, which made the egg float. We can see this by calculating the mass of the combined sugar and water and divide it by the volume. An estimate for the density would be approximately 1.5 . A common rule is when two items or substances are combined, they may end up having a higher weight and density. This in turn can lift and keep an item afloat that may have not kept afloat in tap water. This experiment was an example of what can happen when we adjust densities by adding and modifying elements. It can change the overall weight of a mixture, which can cause the item or substance to float.

What is this process?

Density is the amount of mass that is contained and packed into measured volume. It also demonstrates the heaviness of any substance or object. Density is also related to how tightly packed a material or molecule is in a substance. The density of an object or substance is distinguished by its configuration, weight and temperature. The density of an object is measured in grams per cubic centimetre (grams/cm3 or grams/mL). The process in this experiment was to distinguish, which items had more density. In the experiment that i completed above, the egg had a higher density than the water because it was heavier than waters density (1.0). In this experiment, I had used the following ingredients water, sugar and raw eggs. I believe that these ingredients give us an understanding as to how adding or modifying elements can affect the density of an object or substance. Subsequently, after I had filled the glass with 1 cup of water, I had placed the egg in the water and observed what had happened, and related it to the density of each item. I found that the density of the egg was much more denser and heavier than the density of the water. Therefore, the egg had sunk to the bottom of the glass. Afterwards, in the experiment I decided to add 7 tablespoons of sugar into the water and mixed it in thoroughly. I did this to see whether the density of the water would change. As I was combining the sugar into the water, I noticed that the due to the extensive amount of weight from the sugar, the water's density had increased and it had been altered. Therefore, the eggs density was lighter than the density of the combined water and sugar. Hence this had caused the egg to float above the water and sugar.

How did this piece of work connect to what you already knew?

This piece of work that I have completed connected to what I had already known because prior to completing this experiment, I had known that if a substance or item was denser than the other, then the less dense item will float. I had also known that the less dense an object or substance was, the more it will float. I had already encountered that when someone goes into seawater, at the beach, because the seawater is more dense and heavier than the person, the person floats due to his or her lower density than the seawater. I had also known that oil floats above water like when you go to a harbour where boats are kept, there is all this oil floating above the water. This is because the oil has a lower density than the saltwater, which causes it to float. Prior to completing this learning on density, I had already known that when a leaf is in our pool, it floats because it has a lower amount of density than the water. However when it gets saturated with water it sinks because the density of the leaf and the water on top of it creates a higher density than the water, which causes it to sink below the water. I had also already known that when a small little stone is thrown in water it sinks because it is denser than the water. The small stone has a small volume and a heavier mass this causes it to sink.

How did this extend your thinking?

This extended my thinking because I had never known that by saturating water with sugar could increase the density so much that the egg would end up floating. After conducting this experiment, I have learnt that if you have an item like sugar that can dissolve in water, that item is able to increase the liquids density. I have also learnt that because water has a density of 1.0, if the water is added to an item with a high amount of density, this increases the total quantity of density. I have observed that for example if you had a steel ball, the steel ball is more dense than the egg and the sugar water so therefore the steel ball would still sink to the bottom of the glass. This has extended my thinking because now I know that even if you have added an item into the liquid substance that increases the amount of density; if you place a heavier and denser object or liquid into the substance, the denser object would still automatically sink. I had also never known that each substance has a different density and this has extended my thinking because, now I can see the reason why some substances float above others. In the traffic light experiment, this experiment extended my thinking because it made me realise that different items have different densities and that made me think about what order the solutions needed to be placed in. It also extended my thinking because it made me more aware that if you had a kilogram of feathers and one kilogram of steel, even though they both have the same mass they have different volumes. One kilogram of feathers has a much higher volume and therefore its density would be far less than the steel.

What new ideas did it challenge you to think about?

It has made me think about how boats are able to stay a float considering they are made out of metal. I have now noticed that it is due to the salt water in the sea, because the salt water is denser than the boat, this happens to keep the boat a float. I have also wondered how inflatable devices help to keep a child a float in water. Now I know that because the air in these inflatable devices has a lower density than the water, this helps the child to keep afloat. I also wondered why an inflatable boats were able to hold a person without making them sink. After I thought about this, I realised that there is less density in the inflatable boat because the boat is compressed with air. This air in the boat is less dense than water and when a person is added to that boat because the density of both the inflatable boat and person are less dense than water together, they float. It mainly challenged me to think about volumes of objects. If I am ever filling something into a space (for example a box),and if I was filling the box with feathers, I realise now that because the feathers have a low density, they weigh a small amount, yet they take up a large volume of the box. If the box was to be filled with steel bars, the mass of the box containing the steel will be greater due to the higher density of the steel, even though it occupies the same volume as the feathers.



How does it work?

In this experiment that I have completed, the hot water molecules (which had a red dye) had more kinetic energy than the clear water molecules. This meant that the red water molecules were colliding more and were pushing each other further apart. The red water rose because, heat rises and also because heat is less dense. The red water rose above and through the cold water because heat always rises due to convection. The streams of red water that were visible, were convection currents. Eventually, because of convection currents, the red hot water was able to mix into the cold water and the overall temperature of these two became even. The red food colouring had also diffused throughout the liquid, in this experiment diffusion occurred constantly. The red food colouring molecules had separated from a higher concentration in the hot water, to a much lower concentration in the clear water. This happened to create more of a equal distribution throughout the liquid. This gave the mixture an even, light red complexion.

What is the process?

Convection is simply the movement of molecules in cold and hot liquids and gases. The heat transfer in convection occurs due to the molecular motion in gases and in fluids. When the molecules in liquids and gases are hot they tend to move further apart from each other. This occurs because of the process of convection (the transfer of heat). In this experiment, the type of heat transfer is the physical movement of the cold and hot water. We noticed the hot water molecules (red hot water) had moved to the top because hot molecules rise. The cooler molecules sink to the bottom. In this experiment the thermal energy is transferred in many ways. The thermal energy of the substance in this experiment is able to be determined by adding all the kinetic and potential energy of the liquids molecules. The convection currents that were visible in this experiment were streams of red hot food dye. The food dye had a higher temperature than the water, which caused it to move up to the top of the jar. The dye had moved through the clear cold water due to convection. This happened because convection is when the heat rises and the cold stays below the heat. Some of this movement was also caused by the differences in density, as hot water has a lower density and cold water slightly higher density (making it stay at the bottom of the container)

How did this piece of work connect to what you already knew?

This piece of work that I have completed on convection has connected to what I already knew because prior to knowing what convection was I had an understanding that heat rises and cold substances stay below the heat. I knew this because my house is a two-storey house and in the summer the downstairs area stays quite cool, however upstairs becomes very hot and stuffy. This occurs because of convection. I also had an understanding that the heat from the fireplace transfers and goes above into the chimney because heat rises. It also comes out of the fireplace and rises up to the celling to keep us warm in the winter. I also had observed prior to learning convection, that when steaming vegetables, the water underneath that is being heated creates steam, when it reaches boiling point. This steam and heat then gets transferred above to heat and steam the vegetables. I also knew that when you are having a barbecue, the burning coals underneath the racks on the barbecue transfer their heat to the top of the racks to heat and cook the meat. I already knew that air-conditioning was an example of convection, because when you air-condition a room with cold air, it decreases the overall temperature of the warm room and eventually reaches equilibrium. Equilibrium is the balance of hot and cold air, liquid or substance. All these examples have connected to what I already knew because they are everyday examples of convection that occur in my life.Now I have been able to relate these examples to what i have learnt about the transfer of heat and the process of convection. Also I know that all these things occur because heat rises and the cold stays below the heat.

How did this extend your thinking?

After doing all this research and many different experiments, I have extended my thinking about convection because I never knew that with convection eventually all the temperature of the liquid or object evens out to the same temperature. This piece of work that I have completed has extended my thinking because before learning about convection I knew that the heat rose up, however what I didn't realise was that the cold air stays down, underneath the heat. Now I know that the reason why this occurs is because-of the difference in densities. Heat has a lower density and the cold has a higher density. This is why heats rises and cold goes underneath heat.

I knew that in a fire you are asked to role on the ground, not only to prevent inhaling smoke but also to protect yourself from the heat which is rising.

This has extended my thinking because now I have realised that due to the process of convection, the hot air from the fire rises and the main reason why we are told to get down and role is so that it is easier to breathe and the heat is not as intense below.

Also,I had never known why, when we laid the pool cover over the pool, it was always hot at the top and extremely cold at the bottom of the pools surface. When I thought about it, it extended my thinking because I realised, that due to the suns direct contact with the pool cover, and because of the process of convection, the heat of the water remained at the top and the cold water remained at the bottom of the pool. The heat stayed at the top of the pool because the pool cover prevented the heat from escaping to rise higher and from evaporating. This has extended my thinking because now I know that heat will always want to rise higher, however if it is contained in a certain area (ie a Pool cover or a ceiling), it will be kept in that position.

What new ideas did it challenge you to think about?

This work that I have completed made me think about what happens to the boiling water and how the waters temperature gets evenly distributed. When I thought about it, i realised that when the water begins to be heated, the hot air rises and all the water molecules begin to expand and move around in the pot. The heat gradually gets distributed and transferred to other areas of the pot and cold water starts sinking and the hot water begins to rise. Over time the heat of the pot becomes even and the process still continues.

It also made me think about what happens when the warm water from the ocean rises. After I thought about it, I came to a conclusion that when the warm water from the ocean rises above into the air, it then turns into saturated water droplets that form clouds. This shows the process of convection because hot air rises and the cold water stays below.

I wondered why steam came out of my mum and dads coffee cups, when I realised that due to the heat of the coffee the warm air rises above into the air and forms a steam.



How does it work?

Diffusion is the process in which particles spread from places that have a high concentration to places that have low concentration. This process continues until the particles have been dispersed throughout an area evenly. Diffusion can be called passive because it does not require any energy to occur. Even though diffusion is hard to observe, it has been discovered that the atoms vibrate in the liquid or gas. The hotter the atoms are in a liquid or gas, the faster they move around. In this experiment that I have completed, I have noticed that the atoms in the hot water have moved around so quickly that the diffusion of the red dye occurred a lot faster than the cold water (blue dye). I observed the speed of the red dye and how rapidly it mixed into the water. This is the rate of diffusion in hot water. The colder water diffuses slower due to the gradual movement of the atoms in the liquid. I could see this by viewing how slowly the blue dye (that was tipped into the cold water) took to mix in thoroughly. In this experiment the temperature affected the rate of diffusion. When a liquid or gas is hot, the rate of diffusion will occur a lot faster than in a cold liquid or gas. This is because cooler liquids and gases have a slower process of diffusion. In this experiment it also shows that the high concentrated liquid (food dye) when it was placed into the hot and cold water, the concentration of the food dye decreased because it became diluted when it was added to water. The hot water was able to diffuse the concentrated substance in a quick amount of time however the cold water took a longer time to diffuse the concentrated substance.

What is this process?

Diffusion is the movement of a liquid or gas from an area of high concentration to an area of lower concentration. Diffusion is the outcome of the kinetic properties of the particles of matter. In the process of diffusion the particles will continue to combine and mix together until the particles have evenly been distributed. In this experiment, when the high concentration of food dye was dropped into each glass, the concentration in each glass either quickly or slowly diffused. As the red food dye was dropped into the hot water, the high concentration of the red colouring diffused into the hot water quickly. The high concentration of the red food colouring was diluted as it was diffusing in the hot water. In the cold water the blue food colouring took a much longer time to diffuse. The blue food colouring was at a high concentration but as it was added into the cold water the concentration decreased. Eventually in each glass the food colouring had diffused and had practically mixed throughout the water. The substances had become evenly distributed.

How did this piece of work connect to what you already knew?

This piece of work connected to what I already knew because I had already known that smells and gases travel through the air and get diffused. This piece of work has connected to what I already knew because I knew that perfume had a high concentrated smell and it loses concentration when exposed out of its container or perfume bottle. I also knew that when someone goes to the toilet, the smell of their faeces is at first a high concentrated aroma, however as it is exposed into the toilet, the smell slowly becomes less concentrated. Prior to doing this learning on diffusion, i knew that underarm deodorant has a really high concentrated smell when you inhale it from the container. However, when it is rolled or sprayed onto someones skin the smell travels around and becomes less concentrated. I had also already known that when you smell a candle it is a very strong and concentrated smell, but when the candle is burning the smell becomes less concentrated due to the larger area it is being exposed to and eventually the smell gets diluted. I also already knew that when you smell bugs spray from the bottle, it is a very concentrated smell although when it is sprayed to kill the bugs, the concentration decreases as it is exposed to a larger area. I also already knew that when a person is smoking outside (and I am very close to them) the smell is initially very concentrated and powerful however as you move further away from the person the concentration of the smoke decreases as it gets dissipated in the air.

How did this extend your thinking?

This work has extended my thinking because in the future when I mix cordial with water i realise that the good taste comes from drinking the diluted cordial. If I were to drink the concentrated cordial it would be very strong and disgusting.

I also realise that when the floors are dirty and I add soapy water, it disperses the dirt from a concentrated pile into loose particles that are mopped up by the detergent. The hotter the water, the more rapid is the rate of diffusion and the floors clean up better and quicker. Cold water would take a longer time to do the same job.

What new ideas did it challenge you to think about?

Some new ideas it challenged me to think about was how a tea bag diffuses in the water. After I thought about it, i noticed that the tea inside of the teabag, diffuses throughout the water and eventually the water changes it's colour and taste. The tea in the tea bag is able to do this because the dry tea is concentrated and it gets diffused when added to hot water. Adding it to cold water would take a lot longer.

Another idea it challenged me to think about was when a cube of sugar is placed in a glass of water, i wondered how it diffuses into the water. After thinking about it I realised that the sugar cube is able to gradually dissolve into the water and the molecules of the sugar then get distributed all around in the water.

I have always wondered why the bubbles in soft drinks eventually go flat. Now I have noticed that this occurs because the carbon dioxide bubbles that are pumped into the soft drinks, diffuse out of your soda when you shake the soft drink bottle. This makes the soft drink go flat.

When I am blowing up a helium balloon for my birthday party , when I leave the balloon for a couple of days the balloon leaks out some of it's air. I have always wondered why this occurred and once i had deeply thought about this i had realised that the balloon diffuses air per day and eventually all the helium and air diffuse out of the balloon. After an extended period of time the balloon deflates and contains no more air. I also thought about what would happen when broccoli is cooked. Now i know that the steam diffuses into the vegetable, making it softer and more flexible for eating purposes.