Exp: The effect of materials on insulators
Introduction: Thermal energy, or heat energy, travels through solids, liquids and gases. The more thermal energy something has, the hotter it is, the less thermal energy that something has, the colder it is. Conductors allow thermal energy to transfer through an object to it quickly. They gain a lot of thermal energy quickly as the particles that are in contact with each other can heat up quickly. As heat moves from place to place, there must be something that can prevent human skin feeling the temperature while touching a hot or cold object. These materials that prevent the heat escaping the object is an insulator.
A conductor is matter that allows the process of conduction to take place. Conduction is the transfer of energy through matter that are in direct contact with each other. It is the distribution of thermal energy between atoms within a substance. Conduction can only happen in solids and liquids and heat travels better in solids. It occurs better in solids as the particles in them are closer so the energy can transfer faster. The better the conductor is, the father that the heat energy will transfer from object to object.
An example of a conductor is metal. This is why it is important to use an oven mitt while taking metal trays out of the oven as not only does the food heat up, but the tray. Also, using a metal spoon in a pot is not recommended due to the fact that the spoon will heat up quickly as conduction can take place quickly in the metal. Another example of a conductor is water. This usually takes more time to heat up than a metal as it is a liquid, meaning that the particles are further apart than a solid. Water is usually boiled in a metal pot as the thermal energy transfers from the pot to the water efficiently as they are conductors.
Insulators are materials that do not allow thermal energy to pass through it, this means that the material will stay neutral while the object inside it could be hot or cold. Insulators can keep objects and materials both hot and cold by having small gaps between air particles, which makes sure that the heat does not escape. Insulators must be poor conductors to be able to keep the temperature of the material relatively constant.
An example of an insulator is polystyrene. It is a good insulator as it is made up of numerous gas bubbles. These gasses prevent heat conduction because their particles are far apart, making it difficult for the particles to collide. The particles in polystyrene are so big that they cannot move around much which hinders the transfer of thermal energy. Insulators are also very important in everyday life to keep houses warm and cold when needed throughout the year. In summer, the heat is trapped outside the house, keeping the house cool. When it is cold in winter, the heat is trapped inside and cannot escape and the cold is trapped outside. This aids with reducing the greenhouse gas emissions in the world as people become less reliant on air conditioners and heaters because the house is already hot or cold.
When humans touch metal, it usually feels cold. This is not true because metals conduct heat away from the hand. Humans perceive the heat that it leaving the hand as cold. Insulators stop humans from feeling the heat on metal as the heat can not travel past it. As metal is a conductor of heat, it is important that the insulators work well to prevent the heat coming through the object to the human hand. This allows people to touch the metal while it is hot as they will not be able to feel the heat.
Hypothesis: It is expected that the insulating blanket will be the best insulator and keep the water the hottest as it is thick and is designed to keep things warm or cold. The blanket has very small air bubbles, meaning that the thermal energy is not as likely to travel between the particles. The air will be trapped in the blanket, making sure the heat does not escape or the blanket does not heat up. It is expected that the water temperature in every cup will drop as the insulators are not great enough to keep the water level a constant temperature.
Aim: This experiment aims to investigate how insulating materials effect the heat of water over a certain period of time.
Independent variables:
Type of material
The type of material is being changed to test which material will insulate the hot water the best. The material is around the cup and the stopwatch will determine which insulator is best. This is the only independent variable in the experiment, as it is the only thing that is changing in the experiment. The materials were chosen to be different sizes, shapes and have different thickness which will effect the end temperatures of each cup of water and determine which material is the best insulator.
Dependent variables:
The temperature of water after every 1 minute for 5 minutes
The 1 minute intervals are what we are measuring. Every cup would be measured every minute for 5 minutes to make sure that extra variables were not added. If the cups were measured at different times, it would be very difficult to collect consistent, accurate results. Measuring the water temperature in intervals allows the temperature to be consistently measured at the same time per cup
Controlled variables:
Same amount of water per cup (100ml)
Period of time between each measurement
Type of cup (paper cups)
The initial temperature of water
Type of measurement to test the temperature (glass thermometer)
The amount of water in each cup is the same to keep the results reliable. If 100ml was in each cup, then the temperature of the water would not be different due to the amount of water, but the type of insulator. The interval between each measurement had to be constant to eliminate any unnecessary variables that would impact the results of the experiment. The data that is collected needs to be accurate and reliable to achieve the best results for the experiment. Also, the type of cup that is used in the experiment must stay the same, otherwise, the data would not be valid due to the amount of variables that have been added that should not be in the experiment. The initial temperature of water must be corresponding for each cup as if it is not, the water will decrease in temperature differently, effecting the results. Lastly, the type of device to measure the temperature has to be constant as it would limit the amount of errors with reading the temperature. The measurement device could have a different reading, so it is important that only one type is used. In this experiment, a glass thermometer was used as they are not conductors so the thermometer would not heat up, allowing the thermometer to read more than one cup in the space of 5 seconds without being too inconsistent.
Materials:
Water
Glass thermometer
Stopwatch
6 paper cups
Piece of foam
Measuring cylinder
Beaker
Newspaper
Aluminium foil
Bubble wrap
6 rubber bands
Tape
Insulating blanket
Method:
Wrap each paper cup in one of the different materials
Boil water in a kettle
Pour boiled water into beaker to measure the amount of water
Pour into the 1 of the paper cups (100ml)
Place one thermometer in each cup
Turn the stopwatch on and record the temperature for 0 minutes
Check temperature at 1 minute intervals throughout the 5 minutes
Check final temperature
Do this for every material of cup
Calculate the temperature drop
Graph data using a line graph and a table
The temperature of the water in each cup will be measured for every minute, for 5 minutes. Every cup will be measured at the same time to keep the data that is collected consistent. The water at every interval will be measured with the same glass thermometer as it would impact the results if different thermometers were used per cup. It is important that the method is followed to collect the most accurate and reliable data as possible. Only 100ml of water was used as that was the capacity of the measuring cylinder and using more water would allow the water to cool faster while measuring it out. A kettle was used rather than a Bunsen Burner as it was more reliable and boiled the water more consistently. A line graph and table have been used to show the data in a detailed way. It displays the data better as it can be read easier than other forms of recording data.
Risk assessment:
Results:
A table was used to present the data in the more accurate way as it would precisely display the temperature for every cup at every interval. If just a graph was used, it could be difficult to read exactly what temperature the water was at, at each interval. A graph was used to visually illustrate the results. It allows people to see the decrease in temperature and how the water in each cup decreased between intervals. It also displays how dramatically the water temperature dropped between intervals and how different the starting and ending temperatures were. A second table was used to show the decrease in temperature per material. A table allowed it to be presented in the most accurate way as the numbers were precise. Another graph was not needed to display the results of the decrease in temperature as Figure 1 has already shown it. The start temperature and end temperature can be seen and analysed. An advantage of presenting the data in these ways is that it can appeal to people who like to see things visually and sequentially. It allows people to see the results in an accurate way as the table shows the exact numbers and the graph has been altered to be as detailed as possible. A limitation of presenting the data in this way is that the graph is a bit hard to read due to the amount of materials that have been placed in one graph. It could have been split into two graphs to allow it to be more detailed and this would make it easier to read.
Discussion: This experiment aimed to investigate the best insulator. Different materials were chosen to keep the water hot for the longest time. There were no major apparent trends in the data as each insulator kept the water temperature different to each other. A pattern in the data was that the water temperature dropped quite a bit in every cup as expected as the insulators were not as good quality as to keep the water relatively similar to its starting temperature. This data shown in the line graph is series data as it is displaying the difference between the materials and how the water temperature decreases over time due to quality of the insulator. A strange result was the insulating blanket dropped 8°C between measuring the starting temperature and the first interval. This was strange due to the fact that the insulating blanket has been made to insulate objects, the material has been manufactured to trap the heat in the fabric so it cannot pass. An anomaly was that the water was poured into the insulating blanket cup first so it had approximately 30 seconds to cool down before the starting temperature was taken. This would affect the results and data collected, making it both not accurate and unreliable. The graph shows a negative linear relationship as the temperature of the water is decreasing over time. The foam and paper cups were the best insulators as they were able to trap the transfer of heat and prevent it.
The results of the experiment were slightly different to what was expected in the hypothesis. The hypothesis stated that the insulating blanket would be the best insulator, but this has not been the case as it is the third best insulator. Both the paper cup and foam were the best insulators, decreasing only 14°C. Next best was the bubble wrap which decreased 15°C and then after came the insulating blanket at 16°C. There were anomalies in the data that was collected because the boiling water from the kettle was not poured in each cup at the same time, allowing the temperature of the water to drop in some cups before the time could start. This would affect the results as the starting temperature would be significantly lower than the other cups and it would decrease differently. The hypothesis was only partially incorrect but it could have been completely correct without the anomalies in the data, which altered the end result of the experiment.
The conduction of heat is prevented using insulators, this is relevant to the experiment as the materials were tested to see how they would stop the heat of the water transferring to the outside of the material, resulting in the water staying warm. Insulators stop the transfer of thermal energy between different types of matter. Trapping air in the layers of an object is a common way that insulators keep an object warm. The water temperature dropped significantly in some cups due to the poor insulators. The heat would have found it easy to escape the insulator and heat up the outside of the cup. Insulators are poor conductors as insulators usually does not heat up when the particles of their material has direct contact with a source of heat. The insulators prevent the hot water to conduct heat through the cup and onto the outside of the material.
Insulators are used in real life to keep things warm. An example is a thermos, where it was made to trap the air in the layers so that the heat of the contents can not escape. One of the main features of a thermos flask is the specific double wall. It has been made to suck out the air between the walls during its construction, creating a vacuum, keeping it either hot or cold. The walls minimise the loss of heat of the contents due to conduction and convection. Also, the silver coating prevents the transfer of thermal energy from radiation. Another example of insulators are in houses, the ceiling and walls of a house is stuffed with thermal insulation to trap the heat inside of the house, which is helpful for cold winters, and it keeps the cold out. It also can keep houses cool in summer as it also traps the heat outside the house. This requires a lot of design to keep a house well insulated throughout the whole year. Thermal insulation helps towards reducing greenhouse gas emissions as people would become less likely to use air conditioning and heaters during the year.
Evaluation: This experiment had both many limitations and strengths, which would both affect the data collected. A limitation is that, many human errors could have possibly taken place in this experiment as the method, even though it was accurate, still allowed for human error. A human error could have occurred while reading the thermometer as it depended on what the eye level of the reader was. The thermometer should be at eye level to read it as precisely as possible. Another human error would have occurred while measuring the water with the measuring cylinder as like using the thermometer, the reader would have to be at eye level with the measuring cylinder to read the amount of water as accurately as possible. As the water all came from the same kettle and was not re-boiled, the water started cooling down as soon as it was in the first cup where as it was still very warm when the water was poured in the last cup. The kettle was insulating the water so when the starting temperature was measured, the temperature was lower in some cups due to the fact that they had been sitting out longer. Another limitation was that trials were not performed, which would have improved the results collected generally. The experiment did have strengths though as the data collected was not too inconsistent. The kettle allowed the water to heat up evenly and efficiently, allowing the experiment to take place quickly. This meant that less materials were required because it a Bunsen Burner was used, there would be many more materials, it would take more time, and there would be more risks involved. Another strength is that the glass thermometers had a reading every 2°C, which would limit the human errors in reading it as an approximate number can be made. Even though it would limit the human errors, they would still be made.
The results were not as accurate and reliable as they should have been. As time was limited while performing the experiment, there was not enough time to heat up the water separately for each cup and measure each cup separately for the 5 minutes. Multitasking was the only way the experiment was going to get finished without going into the next period. Time was very short due to the house music timetable and the fact that there was 3 kettles to share with the class, meaning that there were periods where the experiment was not being done due to the fact that no kettles were available. The data would have been more accurate if the water had been re-boiled after each cup had been measured for the 5 minutes as the temperature of the water would not have time to cool before the starting temperature was measured. Also, trials would have made the results both more accurate and reliable as an average temperature could be calculated. An average would rule out any outliers and human errors made in the experiment. The results were quite accurate due to the fact that the thermometers had readings that were detailed. It could be more accurate if a digital thermometer was used but they were not able to be supplied for the experiment. The digital thermometer would have made the data more accurate as it would have given the exact temperature efficiently. Even though there were not many major anomalies in the results, the small human errors have impacted the data collected and have altered the accuracy and reliability of the experiment.
If the experiment was repeated, the data collected would become more reliable and accurate by doing many things that were not doing before. Trials would be made to calculate an average and make the data accurate and reliable. An average could be graphed and put in a table to show the differences between each insulator. Also, a digital thermometer would be used to make the experiment more efficient and accurate as the temperature would be exact. One kettle would be used per group doing the experiment to make sure that the experiment is done as quickly and accurately as possible. Not only would one kettle be used per group, the water would be boiled every cup to every three cups to make sure that the water does not have enough time to cool before the starting temperature got recorded.
Conclusion: It was determined that the best insulator in this particular experiment was the foam material and the paper cup as it trapped the air in its layers, preventing the heat to transfer. The hypothesis was partially incorrect due to the fact that the insulating blanket was not the best insulator. The hypothesis was correct where it stated that every cup would decrease in temperature as the insulators could not keep the water temperature constant. Limitations affected the data as the temperature and measurement of the water might not have been read accurately, trials were not performed. To extend the experiment, more variety of materials could be added, such as a coffee cup and coffee cup lid as this has been made to insulate the contents of a coffee cup and keep them warm. The insulating blanket should have kept the water warmer as the material has been made to insulate objects where as it allowed the temperature to drop. The insulators were used to trap the heat from escaping and preventing the thermal energy to transfer through the cup. Overall, it was concluded that time effected the temperature of the water as the water decreased between the intervals.
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