In May 2018 Kílauea, a volcano on Hawaii’s Big Island, erupted. The volcano exploded, releasing lava, ash and toxic gas. Rivers of lava from the crater flowed into the ocean and jets of steam were released. As the lava flowed into the ocean, it cooled rapidly and glass particles were formed. The emissions from the volcano could have caused damage to lungs, eyes and skin.
Question 1(a)
Lava is a liquid which cools down to form rocks.
Select the name of the physical process that takes place when lava cools down.
▶️Answer/Explanation
Ans:
The physical process that takes place when lava cools down and solidifies into rocks is called “solidification” or “crystallization.” During this process, the molten lava loses heat energy, causing its minerals and components to arrange themselves into a solid, crystalline structure, forming rocks like basalt or pumice, depending on the specific composition of the lava.
Question 1(b)
The composition of lava is different for different volcanoes. The major component of lava is \(\mathrm{SiO}_2\) with oxides of iron and magnesium present in different proportions.
Determine the missing information and complete the table below.
▶️Answer/Explanation
Ans:
In addition to silicon dioxide (\( \mathrm{SiO}_2 \)), the major components of lava typically include magnesium oxide (\( \mathrm{MgO} \)) and iron oxide (\( \mathrm{FeO} \)). So, the missing information in the table should be:
Magnesium oxide: \( \mathrm{MgO} \)
Here’s the completed table:
These oxides, along with other minor components, contribute to the overall composition of lava, which can vary between different volcanoes and volcanic eruptions.
Question 1(c)
Three types of lava are basaltic, andesitic and rhyolitic. The \(\mathrm{SiO}_2\) content for each type of lava lies within the following ranges, all of them expressed in percentage by mass:
A group of geologists analysed the \(\mathrm{SiO}_2\) content in samples of rock from three different volcanoes: Kílauea, Mount Vesuvius and Mount Etna.
A \(2.00 \mathrm{~g}\) sample of rock from Kilauea contained \(0.994 \mathrm{~g}\) of \(\mathrm{SiO}_2\).
A \(2.00 \mathrm{~g}\) sample of rock from Mount Vesuvius contained \(1.16 \mathrm{~g}\) of \(\mathrm{SiO}_2\).
Select the type of rock from Kilauea.
▶️Answer/Explanation
Ans:
To determine the type of rock from Kilauea, we need to calculate the percentage of SiO2 by mass in the rock sample taken from Kilauea.
From the information provided:
Mass of the rock sample from Kilauea = 2.00 g
Mass of SiO2 in the Kilauea sample = 0.994 g
Now, we can calculate the percentage of SiO2 in the sample:
\[
\text{Percentage of SiO}_2 = \left( \frac{\text{Mass of SiO}_2}{\text{Mass of the rock sample}} \right) \times 100
\]
\[
\text{Percentage of SiO}_2 = \left( \frac{0.994 \, \text{g}}{2.00 \, \text{g}} \right) \times 100 = 49.7\%
\]
So, the percentage of SiO2 in the rock sample from Kilauea is 49.7%. Comparing this with the given ranges:
– Basaltic lava has a SiO2 content range of 45.5-55.2%.
– Andesitic lava has a SiO2 content range of 52.0-63.7%.
– Rhyolitic lava has a SiO2 content range of 68.3-77.4%.
Since 49.7% falls within the range of 45.5-55.2%, the type of rock from Kilauea is basaltic.
Question 1(d)
Calculate the percentage of \(\mathrm{SiO}_2\) in the rock sample from Mount Vesuvius.
▶️Answer/Explanation
Ans:
To calculate the percentage of SiO2 in the rock sample from Mount Vesuvius, we can use the information provided:
Mass of the rock sample from Mount Vesuvius = 2.00 g
Mass of SiO2 in the Mount Vesuvius sample = 1.16 g
Now, we can calculate the percentage of SiO2 in the sample:
\[
\text{Percentage of SiO}_2 = \left( \frac{\text{Mass of SiO}_2}{\text{Mass of the rock sample}} \right) \times 100
\]
\[
\text{Percentage of SiO}_2 = \left( \frac{1.16 \, \text{g}}{2.00 \, \text{g}} \right) \times 100 = 58.0\%
\]
So, the percentage of SiO2 in the rock sample from Mount Vesuvius is 58.0%.
Question 1(e)
Using your answer from part (d), select the type of rock from Mount Vesuvius.
▶️Answer/Explanation
Ans:
Based on the calculated percentage of $\rm {SiO}_2$ in the rock sample from Mount Vesuvius, which is 58.0%, we can compare it to the $\rm {SiO}_2$ content ranges for different types of lava:
Basaltic lava has a $\rm {SiO}_2$ content range of 45.5-55.2%.
Andesitic lava has a $\rm {SiO}_2$ content range of 52.0-63.7%.
Rhyolitic lava has a $\rm {SiO}_2$ content range of 68.3-77.4%.
Since 58.0% falls within the range of 52.0-63.7%, the type of rock from Mount Vesuvius is andesitic.
Question 2(a)
It was once believed that each volcano had its own particular type of gas: sulfur dioxide \(\left(\mathrm{SO}_2\right)\) at Mount Etna or hydrogen chloride \((\mathrm{HCl})\) at Mount Vesuvius. This proved to be untrue: volcanic gases are mixtures of water vapour and different gases, such as carbon dioxide \(\left(\mathrm{CO}_2\right)\) and hydrogen sulfide \(\left(\mathrm{H}_2 \mathrm{~S}\right)\). In the case of Kilauea, gaseous hydrogen chloride is a major component.
Suggest why volcano crater lakes typically have \(\mathrm{pH}\) values as low as 0.1 .
▶️Answer/Explanation
Ans:
Volcano crater lakes can have extremely low pH values, such as 0.1, due to the presence of acidic gases, primarily sulfur dioxide (SO2) and hydrogen chloride (HCl), that are released by volcanic activity. Here’s why these lakes have such low pH values:
Acidic Gases Emission: Volcanoes release acidic gases like SO2 and HCl during eruptions. When these gases come into contact with water, they dissolve and form strong acids.
Dissolution of Gases: When SO2 and HCl gases dissolve in water, they react with it to produce sulfuric acid (H2SO4) and hydrochloric acid (HCl). These reactions can be represented as follows:
- SO2 + H2O → H2SO4
- HCl + H2O → H3O+ + Cl–
These reactions increase the concentration of hydrogen ions (H+) in the water, leading to a decrease in pH.
Hydrothermal Activity: Volcano crater lakes are often in contact with hydrothermal systems, where high-temperature water from within the Earth’s crust interacts with surface water. This can further increase the concentration of acidic components and lower the pH.
Deposition of Volcanic Ash: Volcanic eruptions can also deposit ash and volcanic material into the crater lake. This material can leach acidic ions and compounds into the water, further lowering its pH.
Lack of Alkaline Buffers: Volcano crater lakes may lack significant sources of alkaline materials (like limestone or other carbonate minerals) that could neutralize the acidity. Without these buffers, the water remains strongly acidic.
As a result of these factors, volcano crater lakes often have pH values as low as 0.1 or even lower, making them highly acidic and inhospitable to most forms of life.
Question 2(b)
Select the Lewis (dot cross) structure of \(\mathrm{H}_2 \mathrm{~S}\).
▶️Answer/Explanation
Ans:
Question 2(c)
Some noble gases such as helium, neon and argon can also be released into the atmosphere when volcanoes erupt.
Use the periodic table to state the period of argon.
▶️Answer/Explanation
Ans:
Argon (Ar) is located in Period 3 of the periodic table. The periods in the periodic table represent the energy levels or electron shells of the elements, and argon is found in the third period, which means it has three electron shells or energy levels.Question 2(d)
Neon exists as a mixture of isotopes. The most abundant isotopes of neon are \({ }^{20} \mathrm{Ne},{ }^{21} \mathrm{Ne}\) and \({ }^{22} \mathrm{Ne}\).
Determine the number of protons, neutrons and electrons in an atom of \({ }^{22} \mathrm{Ne}\).
▶️Answer/Explanation
Ans:
To determine the number of protons, neutrons, and electrons in an atom of \({ }^{22} \mathrm{Ne}\) (neon-22), we can look at the information provided:
The atomic number of an element represents the number of protons in the nucleus. Neon has an atomic number of 10 because it is the 10th element on the periodic table.
The isotope \({ }^{22} \mathrm{Ne}\) has a mass number of 22 , which represents the total number of protons and neutrons in the nucleus.
Now, we can calculate the number of protons, neutrons, and electrons:
Protons (p+):
The number of protons is equal to the atomic number, which is 10 for neon. So, there are 10 protons in \({ }^{22} \mathrm{Ne}\).
Neutrons (n):
Neutrons can be calculated by subtracting the number of protons from the mass number:
Neutrons \((n)=\) Mass number – Atomic number
Neutrons \((n)=22-10=12\)
So, there are 12 neutrons in \({ }^{22} \mathrm{Ne}\).
Electrons (e–):
Neon is a noble gas, which means it is stable and has a full valence electron shell. The atomic number of 10 also represents the number of electrons in a neutral neon atom because the number of electrons equals the number of protons in a neutral atom. Therefore, there are 10 electrons in \({ }^{22} \mathrm{Ne}\).
In summary, an atom of \({ }^{22} \mathrm{Ne}\) has:
10 protons
12 neutrons
10 electrons
Question 2(e)
Draw the electron configuration of neon.
▶️Answer/Explanation
Ans:
Question 3
In 2003 , I was told by a restaurant owner on a Thai island that local fishermen used to wrap their lunch in banana leaves, which they would then casually toss overboard when done. That was OK, because the leaves decayed and the fish ate the scraps. But in the past decade, he said, because plastic wrap had rapidly replaced banana leaves, the beach was now fringed with a crust of plastic. Beyond the merely unsightly, this plastic congregates in continent-scale garbage-gyres in our oceans, being eaten by fish; then quite possibly it’ll reach your plate … This is a worldwide problem – we can’t point the finger at Thai fishermen. The west started this.
In 2003 , I was told by a restaurant owner on a Thai island that local fishermen used to wrap their lunch in banana leaves, which they would then casually toss overboard when done. That was OK, because the leaves decayed and the fish ate the scraps. But in the past decade, he said, because plastic wrap had rapidly replaced banana leaves, the beach was now fringed with a crust of plastic. Beyond the merely unsightly, this plastic congregates in continent-scale garbage-gyres in our oceans, being eaten by fish; then quite possibly it’ll reach your plate … This is a worldwide problem – we can’t point the finger at Thai fishermen. The west started this.
Question 3(a)
Plastics are synthetic materials. Plastics have high molecular masses meaning each molecule can have thousands of atoms bonded together. In the past, synthetic plastics were made using chemicals from oil.
The two organic compounds shown below, A and B, are used to make two common plastics.
Select the chemical classification of molecules A and B.
▶️Answer/Explanation
Ans:
Molecule A is represented as , and it has a double bond between two carbon atoms. This indicates that it is an example of an alkene.
Molecule B is represented as , and it also has a double bond between two carbon atoms. Like molecule A, it is also an example of an alkene.
Alkenes are organic compounds characterized by the presence of at least one carbon-carbon double bond in their structure. They are commonly used in the production of various plastics and synthetic materials.
Question 3(b)
State the name of each chemical in part (a).
A:
B:
▶️Answer/Explanation
Ans:
In part (a), the chemical names for molecules A and B are as follows:
A: Ethene
B: Propene
Question 3(c)
Molecules A and B can be obtained by breaking down long chain molecules such as decane, \(\mathrm{C}_{10} \mathrm{H}_{22}\).
\[
\mathrm{C}_{10} \mathrm{H}_{22} \rightarrow \mathrm{C}_2 \mathrm{H}_4+\mathrm{C}_3 \mathrm{H}_6+\mathrm{X}
\]
Deduce the molecular formula of the missing product \(\mathrm{X}\).
▶️Answer/Explanation
Ans:
To deduce the molecular formula of the missing product X in the given chemical reaction, we can first determine the total number of carbon (C) and hydrogen (H) atoms on both sides of the equation to ensure that the reaction is balanced.
Starting with the reactant \(\mathrm{C}_{10} \mathrm{H}_{22}\), we have:
– 10 carbon atoms (C) on the left side.
– 22 hydrogen atoms (H) on the left side.
On the right side, we have the formation of ethene (\(\mathrm{C}_2 \mathrm{H}_4\)) and propene (\(\mathrm{C}_3 \mathrm{H}_6\)). We can calculate the total number of carbon and hydrogen atoms formed from these two products:
– From ethene (\(\mathrm{C}_2 \mathrm{H}_4\)), we have 2 carbon atoms and 4 hydrogen atoms.
– From propene (\(\mathrm{C}_3 \mathrm{H}_6\)), we have 3 carbon atoms and 6 hydrogen atoms.
Now, let’s add up the carbon and hydrogen atoms on the right side:
– Carbon atoms (C): \(2 + 3 = 5\) carbon atoms.
– Hydrogen atoms (H): \(4 + 6 = 10\) hydrogen atoms.
To balance the equation, we need to account for the remaining carbon and hydrogen atoms from product X. We already have 5 carbon atoms and 10 hydrogen atoms from the known products, so the missing product X must contain:
– \(10 – 5 = 5\) carbon atoms.
– \(22 – 10 = 12\) hydrogen atoms.
The molecular formula of the missing product X is therefore \(\mathrm{C}_5 \mathrm{H}_{12}\).
Question 3(d)
For many years, non-recyclable plastic waste ended either in landfills or incinerators. However, during the last decade, many countries have implemented thermovalorization. This system makes it possible to recover energy from solid waste. The process – usually called “waste-toenergy”, can be outlined as follows: waste is burned in a plant at very high temperatures. The gases produced are treated with calcium hydroxide. The energy generated by burning waste is used to heat water, which is converted into high pressure steam. This steam is able to drive a turbine and generate electricity, later conveyed to the public grid.
State why calcium hydroxide is added to the gases produced during the incineration of waste.
▶️Answer/Explanation
Ans:
Calcium hydroxide (Ca(OH)2) is added to the gases produced during the incineration of waste for several important reasons:
Acid Gas Neutralization: The combustion of waste materials can produce acidic gases, such as sulfur dioxide (SO2) and hydrogen chloride (HCl). These acidic gases can be harmful to the environment and contribute to air pollution. Calcium hydroxide is an alkaline substance that can effectively neutralize these acidic gases by reacting with them to form less harmful compounds. For example, it can react with sulfur dioxide to form calcium sulfate (CaSO4) and hydrogen chloride to form calcium chloride (CaCl2).
Air Pollution Control: Adding calcium hydroxide helps control the emission of acidic pollutants, which is crucial for meeting environmental regulations and reducing the harmful effects of acid rain and air pollution.
Particulate Removal: Calcium hydroxide can also act as a sorbent to capture fine particulate matter (PM) that may be present in the waste gases. This helps to reduce the emission of particulate pollutants into the atmosphere.
Improved Efficiency: The addition of calcium hydroxide can improve the efficiency of certain pollution control systems by enhancing the removal of acidic gases and particulate matter. This ensures that the waste-to-energy plant operates more effectively.
In summary, calcium hydroxide is added to the gases produced during waste incineration to neutralize acidic pollutants, control air pollution, and enhance the overall performance of the waste-to-energy process while reducing environmental impacts.
Question 3(e)
State the physical change taking place between stages 2 and 3 of the thermovalorization process.
▶️Answer/Explanation
Ans:
boiling
Question 3(f)
In most countries, incineration of waste in this type of process is subject to strict regulations. Suggest one requirement that should be included in order to reduce the environmental impact of the process.
▶️Answer/Explanation
Ans:
Accept any two reasonable responses, for example
• waste should not contain any materials that could produce
hazardous/toxic/explosive substances during incineration
• atmospheric emissions should be controlled with the proper equipment
Question 3(g)
There has been a move away from non-biodegradable plastics to biodegradable plastics. The rate of biodegradation was tested for a given plastic. Pellets of the plastic were ground in order to obtain three samples, A, B and C with different size particles. The samples were buried in soil and tested over 50 days. The data is shown in the graph below.
List the order of the three samples in order of increasing particle size. Justify your answer.
▶️Answer/Explanation
Ans:
A — C — B (increasing size)
A had the fastest rate of biodegradability / breakdown
rate of reaction increases with decreasing particle size
or
the smaller the particles, the higher the surface area and the faster the reaction
Question 4
Glow sticks produce light in a chemical reaction. They can be used by the military, by divers or just for fun.
Glow sticks work by combining two chemicals to produce light in a chemical reaction known as chemiluminescence. One of the chemicals in the glow stick is a catalyst.
The catalyst is separated from the other reactants inside a sealed tube.
Keeping the catalyst separate prevents the reaction starting until light is needed. Once the tube containing the catalyst is broken, the reaction will produce light.
Question 4(a)
Outline the function of a catalyst.
▶️Answer/Explanation
Ans:
The function of a catalyst in a chemical reaction, such as the chemiluminescence reaction inside a glow stick, can be outlined as follows:
Initiating or Speeding Up the Reaction: A catalyst is a substance that can initiate or speed up a chemical reaction without being consumed in the process. It lowers the activation energy required for the reaction to occur, allowing it to proceed more rapidly than it would without the catalyst.
Providing an Alternative Reaction Pathway: Catalysts work by providing an alternative pathway for the reaction to follow, which has a lower activation energy barrier. This alternative pathway allows more reactant molecules to overcome the energy barrier and participate in the reaction.
Facilitating the Formation of Products: By lowering the activation energy, the catalyst promotes the formation of products from the reactants. In the case of glow sticks, it helps convert the chemical energy stored in the reactants into light energy (chemiluminescence) more efficiently.
Remaining Unchanged: Importantly, a catalyst remains unchanged and is not consumed during the reaction. This means it can be used repeatedly to facilitate the same chemical reaction without being used up.
Controlled Timing: In the context of glow sticks, the catalyst is initially kept separate from the other reactants to prevent the reaction from starting until it’s needed. Breaking the tube containing the catalyst allows for the controlled initiation of the chemiluminescent reaction, ensuring that the light is produced when desired.
In summary, a catalyst functions by lowering the activation energy of a chemical reaction, providing an alternative reaction pathway, and facilitating the formation of products without itself being consumed. It allows reactions to occur more quickly and efficiently and can be used in a controlled manner to initiate reactions at specific times or under certain conditions.
Question 4(b)
One of the chemicals involved in the reaction is called phenyl oxalate. This is a complex molecule. A simplified version of the reaction taking place in a glow stick is shown below:
Select the name of the organic functional group highlighted below from the phenyl oxalate molecule.
▶️Answer/Explanation
Ans:
Ester Functional Group: R-COO-R’
In the ester functional group, R and R’ represent alkyl or aryl groups, and the central carbon atom is double-bonded to one oxygen atom and single-bonded to another oxygen atom, which is also bonded to an organic group.
Esters are characterized by their sweet, fruity, and pleasant odors and are often found in naturally occurring fragrances and flavor compounds. They are commonly used in the synthesis of various organic compounds, including those used in glow stick reactions for chemiluminescence.
Question 4(c)
A student is interested in the length of time that glow sticks will glow at different temperatures. The student placed identical glow sticks into water at various temperatures and then broke the inner tube, starting the reaction.
Measure the missing temperature.
▶️Answer/Explanation
Ans:
Question 4(d)
Identify the variables for this investigation.
Independent variable:
Dependent variable:
Control variable one:
Control variable two:
▶️Answer/Explanation
Ans:
Independent variable: temperature
Dependent variable: time taken for the glow stick to stop glowing
• type or colour of glow stick
• volume of water
• time to equilibrate
Question 4(e)
Formulate a suitable hypothesis for the investigation.
If:
Then:
Because:
▶️Answer/Explanation
Ans:
then the length of time the glow stick will glow will decrease
because the rate of the reaction increases
Question 4(f)
The student calculated average data for the investigation and plotted a graph shown below:
Predict the time taken for the glow stick to stop glowing at \(15^{\circ} \mathrm{C}\).
▶️Answer/Explanation
Ans:
Minutes or min(s)
Question 4(g)
A glow stick contains \(6.58 \times 10^5\) molecules of phenyl oxalate. The time for the reaction to stop at \(20^{\circ} \mathrm{C}\) is 260 minutes. Calculate the rate at which the phenyl oxalate molecules are used up at this temperature. You should include appropriate units in your answer.
▶️Answer/Explanation
Ans:
Question 5
Sunlight is important for a number of reasons; it is used by plants to produce glucose, harnessed by solar panels or solar cells to produce useable energy and used by melanin in the skin to provide us with vitamin D. Melanin production in the skin prevents too much exposure from ultra-violet (UV) light and hence lowers the risk of health problems.
When in the sun, it is recommended that we apply sunscreen every 20-30 minutes as the effectiveness of its protection is limited to this length of time. Sunscreen is usually a mixture of several different chemical components. The main ones are homosalate, octisalate, titanium oxide and zinc oxide.
When white UV-reactive beads are exposed to UV light the beads will change colour. A student decided to investigate how many UV-reactive beads changed colour when protected from UV light by three different sunscreens. The sunscreen was spread over the lid of the container.
Question 5(a)
Use the information above to state which is the most effective sunscreen.
▶️Answer/Explanation
Ans:
Question 5(b)
The diagram below shows the light emitted by different sources. The experimental method uses a UV lamp. Outline why this lamp is not a good model for natural sunlight.
▶️Answer/Explanation
Ans:
UV lamp only emits a narrow band of light / UVA only
Question 5(c)
Using the equipment below, design an investigation to determine which of the individual chemical compounds present in Solar Flex sunscreen provides the best protection from the sun. In your answer you should include:
You are provided with the following equipment:
Lotions of each of Homosalate, Octisalate, Octinoxate, Titanium dioxide
UV reactive
beads Petrie dishes
UV Lamp
$\bullet$ an identification of the variables
$\bullet$ a list of the additional equipment you will use
$\bullet$ details of your method for manipulating the variables
$\bullet$ details of the data you will collect
$\bullet$ how you will ensure that your method is safe.
▶️Answer/Explanation
Ans:
$\boldsymbol{y}$ axis: Energy / MJ Tonne$^{$\bullet$1}$
Question 6(a)
Solar Flex was one of the sunscreens investigated in question 5.
Solar Flex’s composition is given below:
Homosalate, Octisalate, Octinoxate, Titanium dioxide
The research question suggested was:
Outline how you will use the data from the investigation in question 5 to decide if the research question is supported.
▶️Answer/Explanation
Ans:
To determine if titanium dioxide is the best blocker of UV light among the components of Solar Flex sunscreen, you can use the data obtained from the investigation in question 5. Here is an outline of how you can use the data to evaluate and support your research question:
1. Collect Data on UV Blockage Efficiency:
$\bullet$ Obtain the data from the investigation regarding the UV blocking efficiency of each component (Homosalate, Octisalate, Octinoxate, and Titanium dioxide) present in Solar Flex sunscreen.
$\bullet$ This data may include the SPF (Sun Protection Factor) values or the percentage of UV rays blocked by each ingredient.
2. Compare UV Blockage Efficiency:
$\bullet$ Analyze the data to compare the UV blocking efficiency of each ingredient. You can create a comparative table or graph to visualize the differences.
$\bullet$ Look for trends or patterns that indicate which ingredient provides the most effective UV protection.
3. Consider Broad$\bullet$Spectrum Protection:
$\bullet$ It’s essential to consider not only the UVB (shortwave UV) but also UVA (longwave UV) protection. Determine if the data includes information on broad$\bullet$spectrum protection provided by each ingredient.
$\bullet$ Titanium dioxide is known for its ability to provide both UVA and UVB protection, so this aspect should be considered in your analysis.
4. Assess Other Factors:
$\bullet$ Take into account any other relevant factors, such as potential side effects, skin sensitivity, or stability of the ingredients, which may affect their suitability as a sunscreen component.
5. Statistical Analysis (if applicable):
$\bullet$ If the data allows for statistical analysis, you can perform tests to determine if the differences in UV blocking efficiency between the ingredients are statistically significant.
6. Conclusions:
$\bullet$ Based on the analysis of the data, draw conclusions about whether titanium dioxide appears to be the best blocker of UV light among the components of Solar Flex sunscreen.
$\bullet$ Consider the overall UV protection, any statistical significance, and other factors that could impact the effectiveness of the ingredients.
7. Supporting Evidence:
$\bullet$ Provide evidence from the investigation data to support your conclusion. This may include specific SPF values or percentages of UV blocked by each ingredient.
8. Discussion and Implications:
$\bullet$ Discuss the implications of your findings and how they relate to the research question. Address whether the data supports the hypothesis that titanium dioxide is the best UV blocker in Solar Flex.
9. Limitations and Future Research:
$\bullet$ Mention any limitations in the investigation data or methodology and suggest areas for future research to further explore the effectiveness of sunscreen ingredients.
By following this outline and thoroughly analyzing the data from the investigation in question 5, you can determine if titanium dioxide is the best blocker of UV light among the ingredients in Solar Flex sunscreen and provide a well$\bullet$supported conclusion.
Question 6(b)
Suggest an extension that could be made to the investigation into the effectiveness of the sunscreen ingredients.
▶️Answer/Explanation
Ans:
An extension to the investigation into the effectiveness of sunscreen ingredients could involve studying the long-term effects of prolonged exposure to UV radiation on skin protection. Specifically, you could conduct a study to assess the durability and stability of the sunscreen ingredients under real-world conditions. Here’s how this extension could be structured:
Research Title: Long-Term Durability and Stability of Sunscreen Ingredients: A Real-World Assessment
Objective: To investigate how sunscreen ingredients, including Titanium dioxide, in Solar Flex sunscreen, perform in terms of durability and stability when exposed to extended periods of UV radiation under real-world conditions.
Methodology:
Selection of Test Subjects:
- Choose a group of human subjects with different skin types.
- Ensure informed consent and compliance with ethical guidelines.
Sunscreen Application:
- Apply Solar Flex sunscreen, which contains the ingredients under investigation (Homosalate, Octisalate, Octinoxate, and Titanium dioxide), to specific areas on the subjects’ bodies.
UV Exposure:
- Subjects should engage in regular outdoor activities, which naturally expose them to UV radiation over an extended period.
- Monitor the duration and intensity of UV exposure, taking into account factors such as weather conditions and geographic location.
Regular Assessments:
- Conduct regular assessments of the sunscreen’s effectiveness at protecting against UV radiation.
- Use a combination of methods, such as SPF measurements, UV photography, and skin assessments, to evaluate sunburn prevention and skin damage over time.
Data Collection:
- Collect data on the sunscreen’s performance over an extended period (e.g., several weeks or months).
- Track any changes in the SPF protection, UV blocking efficiency, and overall effectiveness of the sunscreen ingredients.
Skin Health Monitoring:
- Continuously monitor the skin health of the subjects.
- Assess any signs of skin damage, sunburn, or other adverse effects associated with prolonged UV exposure.
Environmental Factors:
- Consider environmental factors that may affect sunscreen performance, such as water exposure (e.g., swimming or sweating) and temperature fluctuations.
Data Analysis:
- Analyze the data to determine which sunscreen ingredients demonstrate the best durability and stability over time.
- Assess if Titanium dioxide maintains its UV protection properties under extended UV exposure.
Discussion and Implications:
- Discuss the implications of the findings for individuals using sunscreen for extended periods, such as outdoor workers or frequent beachgoers.
- Consider whether certain ingredients prove more effective in real-world scenarios.
Recommendations:
- Provide recommendations for sunscreen manufacturers and users based on the research findings.
- Suggest improvements or modifications to sunscreen formulations if necessary.
Conclusion and Future Research:
- Summarize the conclusions drawn from the investigation and suggest avenues for future research, such as investigating the impact of sunscreen reapplication and the role of different environmental conditions.
This extension to the investigation would provide valuable insights into the long-term effectiveness of sunscreen ingredients, helping individuals make informed choices about sun protection in real-world settings and potentially guiding the development of more durable and stable sunscreen formulations.
Question 6(c)
Chemists are analysing a new chemical, myponium, to see if it can be used to block out UV light in sunscreens. The chemists do this by making different concentrations of myponium and measuring how much light is absorbed. Absorbance is measured in absorbance units \((\mathrm{AU})\). The concentrations of myponium are very low; they are measured in micromoles \(\mathrm{dm}^{-3}\left(\mu ~\mathrm{mol}~ \mathrm{dm}^{-3}\right)\).
The results are shown below:
Plot a graph of the absorbance vs concentration of myponium. You should label the axes, give your graph a suitable title and add a line of best fit.
Title_________
$x \text { axis label: }$ ______
$y \text { axis label: }$ ______
▶️Answer/Explanation
Ans:
Title – A title that links Absorbance and concentration (of chemical X)
two data points plotted correctly
all data points plotted correctly
line of best fit to start at (0,0) and go through all points except 70μmol dm-3
axis labels: concentration on x axis and absorbance on y axis
unit of concentration μmol dm-3
Question 6(d)
Comment on the reliability of the data.
▶️Answer/Explanation
Ans:
anomalous data point at 70 (μmol dm-3)
or
there is only one trial or averages are not plotted
Question 7
Climate change is a global threat recognized by the Intergovernmental Panel on Climate Change (IPCC). The cause of climate change is thought to be due to increased levels of greenhouse gases, mainly carbon dioxide. Increased levels of carbon dioxide have resulted in an increase in the average temperature of the Earth. In the future, severe droughts are predicted in some regions, while floods are predicted in other areas. Both situations will lead to famine and increased poverty.
In the natural carbon cycle, carbon dioxide comes from sources such as respiration, volcanic eruptions, fossil fuels and industrial processes such as cement making. One way that carbon dioxide can be removed from the atmosphere is by photosynthesis in plants. The plants act as a natural carbon dioxide sink. Extensive deforestation means that less carbon dioxide is trapped in trees so levels are increasing in the atmosphere.
Question 7(a)
Use the graph to identify the region that had the smallest increase in water consumption between 1900 and 1980 .
▶️Answer/Explanation
Ans:
Australia and Oceania
Question 7(b)
Use the graph to state the water consumption in Asia in 1995.
Using the reactivity series on the left, state a suitable hypothesis that could be tested using the data in the table in part (a).
▶️Answer/Explanation
Ans:
\(2150\pm 100\)
Billion and \(\mathrm{m}^3\) or cubic metres
Question 7(c)
Suggest a reason why the water consumption in Asia has increased dramatically during the period shown on the graph.
▶️Answer/Explanation
Ans:
The dramatic increase in water consumption in Asia during the period shown on the graph can be attributed to population increase. As the population in Asia grows, there is a higher demand for water resources to meet the needs of households, agriculture, industry, and various sectors of the economy. This increasing population puts pressure on the available freshwater sources, leading to higher water consumption rates to support the expanding communities and economies in the region.
Over 15 million people in the United States of America (USA) obtain their water from private water wells. The water in the wells comes from groundwater. When it rains, any water that is not used by plants or trees flows through layers of soil and rocks and into the ground. This is the water that is used in water wells. If the ground is contaminated due to pesticides, fertilizers, sewage, landfills or other urban runoffs, then the water also becomes contaminated.
The table below shows contaminants that may be present in water from wells and the symptoms or diseases they cause.
Kamal and Sandra have moved into a home in the USA that has a private water well. They need to purchase a filtration device to use in their home to make their water safe for drinking. They are choosing between a ceramic core unit and an activated carbon unit. The information for each unit is shown in the table below. An individual would typically use around \(2 \mathrm{dm}^3\) of water a day for drinking and cooking.
Question 7(d)
Select the most important feature of the filter that is needed in a filtration device. Justify your answer.
Justification:
▶️Answer/Explanation
Ans:
The most important feature of the filter that is needed in a filtration device for Kamal and Sandra’s private water well is the filter pore size.
Justification:
Filter pore size determines the size of particles or contaminants that the filter can effectively remove from the water. In the context of their well water, which may be contaminated by various contaminants such as E. coli, Giardia, Hepatitis A, heavy metals, fuel, and nitrates, the filter’s ability to block these contaminants is critical for ensuring safe drinking water.
Comparing the two filter options:
Ceramic Core Unit: This filter has a smaller filter pore size of 0.22 μm. This means it can effectively block smaller particles, including bacteria like E. coli and parasites like Giardia, which have sizes ranging from 0.5-6 μm. This is an important feature for ensuring that harmful microorganisms are removed from the water.
Activated Carbon Unit: This filter has a larger filter pore size of 0.60 μm. While it can still filter out some contaminants, it may not be as effective at blocking smaller microorganisms and heavy metals. The larger pore size might allow some contaminants to pass through, potentially compromising the quality of the drinking water.
Given that Kamal and Sandra are concerned about the safety of their well water and the potential presence of contaminants, a filtration device with a smaller filter pore size (like the ceramic core unit) is the most important feature. It provides an added layer of protection by effectively removing a broader range of contaminants, including those that could cause health issues or water quality problems.
Question 7(f)
Using the information in the tables above, explain the advantages and disadvantages of using a ceramic core unit compared to an activated carbon unit for personal drinking, when obtaining water from a private well. In your answer, you should:
$\bullet$ describe the advantages and disadvantages of a ceramic core unit compared to the activated carbon unit
$\bullet$ justify which would be the most suitable filter for Kamal and Sandra.
▶️Answer/Explanation
Ans:
Advantages and Disadvantages of a Ceramic Core Unit Compared to an Activated Carbon Unit for Personal Drinking from a Private Well:
Ceramic Core Unit:
Advantages:
Effective Removal of Microorganisms: The ceramic core unit has a small filter pore size (0.22 μm), making it highly effective at blocking microorganisms such as bacteria (e.g., E. coli) and parasites (e.g., Giardia) commonly found in contaminated well water. This ensures the water is microbiologically safe to drink.
Longer Filter Life Span: The ceramic core unit has a filter life span of 12 months, which means it needs replacement less frequently compared to the activated carbon unit. This can lead to cost savings in the long run.
Disadvantages:
Limited Effectiveness Against Some Chemical Contaminants: Ceramic filters may not be as effective in removing certain chemical contaminants like heavy metals or chemicals with smaller molecular sizes. They are primarily designed for microbiological removal.
Slower Water Flow Rate: The ceramic core unit has a relatively slower water flow rate (1.8-3.8 dm³/min), which means it might take longer to fill containers or provide water for cooking. This can be inconvenient when there is a high demand for water.
Activated Carbon Unit:
Advantages:
Effective Chemical Contaminant Removal: Activated carbon filters are excellent at adsorbing a wide range of chemical contaminants, including organic compounds, chlorine, and volatile organic compounds (VOCs). They can improve the taste and odor of water.
Suitable for Broad Water Temperatures: The activated carbon unit can operate effectively over a broader range of temperatures (-1-51°C) compared to the ceramic unit. This makes it suitable for use in varying weather conditions.
Disadvantages:
Limited Microbiological Removal: Activated carbon filters may not be as effective at removing microorganisms like bacteria and parasites as ceramic filters due to their larger filter pore size (0.60 μm).
Shorter Filter Life Span: The activated carbon unit needs more frequent filter replacement with a life span of 26 months. This can lead to higher long-term operating costs.
Justification for Kamal and Sandra:
For Kamal and Sandra, who are obtaining water from a private well, the most suitable filter option would likely be the ceramic core unit. Here’s why:
Safety Concerns: Their primary concern should be the safety of their well water, especially considering the potential presence of contaminants like E. coli, Giardia, and Hepatitis A. The ceramic core unit, with its smaller filter pore size, is more effective at removing these microorganisms, ensuring the water is microbiologically safe to drink.
Cost-Efficiency: While the ceramic unit has a slightly higher upfront cost and a shorter filter life span compared to the activated carbon unit, its effectiveness in microbiological removal and the importance of water safety make it a cost-effective choice in the context of health and well-being.
Chemical Contaminants: Although the activated carbon unit excels at removing chemical contaminants, Kamal and Sandra’s primary concern should be microbiological safety, given that they are obtaining water from a private well. They can address taste and odor concerns separately, if necessary.
In summary, prioritizing microbiological safety and considering the well water’s potential contamination sources, the ceramic core unit is the more suitable choice for Kamal and Sandra’s personal drinking water needs.
Question 8
The paragraph below shows some different techniques that can be used to make water safe to drink.
Access to clean drinking water is a global issue, as increasing industrialization can lead to contamination of lakes, rivers and streams.
With a growing world population and as cities grow, access to drinking water becomes even more important.
In more economically developed countries, unclean water is treated to produce clean water, which is used for drinking, bathing, laundry and washing dishes.
Urban water treatment is a large-scale process that takes place in water treatment facilities.
Surface water can be treated to make clean drinking water using different techniques. A common technique uses microfiltration and ultrafiltration to remove microorganisms and suspended solids like sand, dirt and debris. This is a low-cost process.
A newer technology uses nanofiltration membranes. The rate of water treatment is faster with this method than with microfiltration, so more water can be treated in a cost-efficient manner. However, the industrial facility is expensive to construct due to the price of the nanofiltration components.
Our sources of surface water and groundwater are fast running out because of population growth and climate change. Seawater is the most abundant source of water on Earth. There are \(182 \times 10^9 \mathrm{dm}^3\) of seawater for each person on Earth. However, the salt content makes it unsuitable for drinking.
Desalination by reverse osmosis is used to treat seawater to make it safe to drink. It is an expensive and energy-intensive technology.
The removed ions are returned to the sea, potentially increasing the temperature and salt concentration of seawater.
Both nanofiltration and desalination allow for the filtration of heavy metals, such as nickel and lead. In reverse osmosis, the heavy metals can clog the membranes.
The table below shows some information about some different technologies used for water treatment. The volumes in this table are very large. For comparison, the volume of any Olympic-sized swimming pool is \(25000 \mathrm{~m}^3\).
The city planners in a coastal region are planning for expansion over the next 10 years. One of their priorities is to ensure an adequate water supply for the increased population. The city is located next to the ocean with farming land next to the city boundaries. The main industry in the city is metal recycling.
Using your knowledge of water purification techniques, information from the video and your wider MYP studies, discuss and evaluate the different technologies available for water treatment. In your answer, you should include:
$\bullet$ a comparison of the economic implications of each of the three technologies
$\bullet$ an example of the environmental impact of each of the three technologies
$\bullet$ a suggestion of which technology would not be suitable for the city
$\bullet$ an outline of the social aspects of the building and running of a water purification facility
$\bullet$ an appraisal of which purification process should be used for the city.
▶️Answer/Explanation
Ans:
Comparison of Water Purification Technologies:
Microfiltration and Ultrafiltration:
- Economic Implications: This technology has a moderate initial building cost and low replacement parts cost. Labor costs are also relatively low. It has a lifespan of 15 years, which provides good long-term value.
- Environmental Impact: Microfiltration and ultrafiltration effectively remove suspended solids and microorganisms, improving water quality without significant environmental drawbacks.
- Suitability for the City: This technology is suitable for the city due to its cost-effectiveness and minimal environmental impact.
- Social Aspects: The operation of this facility requires low skill labor, contributing to local employment opportunities.
Nanofiltration:
- Economic Implications: Nanofiltration has a high initial building cost and moderate replacement parts cost. Labor costs are relatively low. The technology’s shorter lifespan (3-5 years) can increase long-term operating costs.
- Environmental Impact: Nanofiltration effectively removes suspended solids, microorganisms, and heavy metal ions. However, its higher energy requirements may have a moderate environmental impact due to energy consumption.
- Suitability for the City: While effective, the higher initial cost and shorter lifespan may pose economic challenges for the city.
- Social Aspects: Similar to microfiltration and ultrafiltration, nanofiltration requires low skill labor for operation.
Desalination by Reverse Osmosis:
- Economic Implications: Reverse osmosis has a high initial building cost, low replacement parts cost, and high labor costs (requires high skill labor). Its shorter lifespan (2-3 years) can lead to higher long-term costs.
- Environmental Impact: Reverse osmosis is energy-intensive and may increase the temperature and salt concentration of seawater when used for desalination. It can have a significant environmental impact due to energy consumption.
- Suitability for the City: Given the coastal location, reverse osmosis may be suitable for treating seawater. However, its high operating and maintenance costs need to be considered.
- Social Aspects: High skill labor is required for operation, which may pose employment challenges if skilled labor is scarce.
Appraisal and Suggestion:
Considering the coastal location of the city with access to seawater, and the need for an adequate water supply for an expanding population, reverse osmosis desalination could be a suitable option. However, its high initial building cost, energy-intensive nature, and potential environmental impact should be carefully assessed.
To make an informed decision, the city planners should consider a combination of technologies. For example, microfiltration and ultrafiltration could be employed for treating surface water from nearby sources, reducing the load on the desalination facility. This approach could help balance economic considerations while ensuring a sustainable and reliable water supply.
Overall, the choice of purification process should be made based on a comprehensive assessment of economic, environmental, and social factors, with a focus on long-term sustainability and meeting the city’s water needs.