IB MYP 4-5 Chemistry chapter 2 : Evidence – Practice Questions

Question:

A yellow precipitate is produced when two colorless solutions are added together.

▶️Answer/Explanation

Ans: Qualitative observation

Question:

A vigorous reaction occurs and bubbles are seen on the surface of the metal in the solution.

▶️Answer/Explanation

Ans: Qualitative observation

Question:

Hydrogen gas is produced during the reaction.

▶️Answer/Explanation

Ans: Inference

Question:

A temperature rise of 8°C is recorded.

▶️Answer/Explanation

Ans: Quantitative observation

Question:

The metal turns a brown color. It has rusted.

▶️Answer/Explanation

Ans: Qualitative observation and inference

Question:

The mass of the reaction mixture decreases as gas escapes from the conical flask.

▶️Answer/Explanation

Ans: Inference

Question:

There is a loss of mass of 4.3 g over the first 120 s of the reaction.

▶️Answer/Explanation

Ans: Quantitative observation

Question:

List three observations of what happens when sodium and potassium metal are dropped into water.

▶️Answer/Explanation

Ans: The metal floats on the surface of the water; metal reacts with water and quickly disappears; a gas is produced.

Question:

What flame color did you observe from each reacting metal?

▶️Answer/Explanation

Ans: Sodium produces an orange/yellow colored flame and potassium a lilac colored flame.

Question:

What did you notice about the level of reactivity of sodium compared to potassium?

▶️Answer/Explanation

Ans: The reaction of sodium with water is less vigorous compared to potassium with water.

Question:

What does the color of the UI tell you about the initial and final pH of the water solution? Estimate the pH of the resulting solution.

▶️Answer/Explanation

Ans: An initial colour of green indicates the water has a pH of approximately 7.0. After the reaction, the colour changes from green to blue/purple indicating the pH has increased to above 9.0.

Question:

Write word equations to describe the reactions of sodium and potassium with water.

▶️Answer/Explanation

Ans: sodium + water → sodium hydroxide + hydrogen
potassium + water → potassium hydroxide + hydrogen

Question:

Using the skills developed in Chapter 1, Balance, construct balanced chemical equations for both reactions.

▶️Answer/Explanation

Ans: 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)

Question:

Consider some typical metals and their physical and chemical characteristics. For example, a lead fishing sinker is denser than water and sinks to the bottom of the lake; an iron nail corrodes in air, but very slowly. Consider what happens if you drop a piece of copper, aluminium or iron into water. Describe how the behavior of the alkali metals are different from other metals.

▶️Answer/Explanation

Ans: Alkali metals are soft and can be cut with a knife; alkali metals are less dense than normal metals and float on water; alkali metals are stored under oil to prevent a reaction with oxygen and water; react vigorously with water; oxidize rapidly on exposure to air.

Question:

Why is it an advantage for chemists to have access to elements that are inert?

▶️Answer/Explanation

Ans: Elements that are inert are useful as they do not react with other elements and compounds.

Question:

Describe some applications in which this property can be exploited.

▶️Answer/Explanation

Ans: One useful application of inert gases is the storage of reactive elements in sealed glass tubes surrounded by an inert gas.

Question:

Why does Malta, which is 99% dependent on fossil fuels, have less of an impact on global demand than China which is 88% dependent on fossil fuels?

▶️Answer/Explanation

Ans: Malta has a far smaller impact on the global demand for fossil fuels than China because Malta is a much smaller country with a much smaller population compared to China, one of the most
densely populated countries in the world.

Question:

Look at the charts and the illustration of fractional distillation. Explain which crude oil is best suited to the production of gasoline.

▶️Answer/Explanation

Ans: Gasoline is a volatile liquid with a low boiling point. It is extracted from crude oil and is considered one of the light products. Saharan crude oil from Algeria has the highest proportion of light products.

Question:

Explain why crude oil from Venezuela is called heavy oil. How does the molecular mass of the most common hydrocarbon in this crude oil differ from the hydrocarbons commonly found in Saharan crude oil?

▶️Answer/Explanation

Ans: Crude oil from Venezuela is called heavy oil as it has a high percentage of long carbon chain hydrocarbons. The majority of products made from this crude oil have a high density such as bitumen, lubricating oils and fuel oils.

Question:

The terms sweet crude oil and sour crude oil refer to the sulfur content of the crude oil. Crude oil with less than 0.5% sulfur content is classified as sweet. Which crudes on this graph are considered sweet oil?

▶️Answer/Explanation

Ans: Saharan (Algeria) and Brent (North Sea) are classified as being sweet crude oil.

Question:

Sulfur is corrosive. Suggest reasons why sweet oil is easier to refine and is preferred by refineries? Why does sweet oil command a higher price per barrel?

▶️Answer/Explanation

Ans: Sour crude oil has a higher percentage of sulfur. The corrosive nature of sulfur would result in damage to the infrastructure of the oil refinery. This higher cost of maintenance will reduce the
company profit margin. Sweet crude oil commands a higher price per barrel as there are less associated costs with its refining.

Question:

Determine the relationship between the number of carbons and the hydrogens in alkanes: if an alkane has n carbons, how many hydrogens does it have? Write your answer in the form CnH?.

▶️Answer/Explanation

Ans: CnH2n+2

Question:

Where else do we use rules to govern communication in both writing and speech? Why are these protocols essential for clear communication of meaning?

▶️Answer/Explanation

Ans: In the field of Biology, we use the classification rules to give plants and animals specific names. These names are globally accepted. These names are Kingdom, Phylum, class, order, family, genus and species.

Question:

Re-write the equation for the hydrogenation of ethene using structural formulae.

▶️Answer/Explanation

Ans:

Question:

What reaction could be happening between bromine water and the alkene to cause the color change?

▶️Answer/Explanation

Ans: Similar to the process of hydrogenation, bromine reacts with ethene to form 1,2dibromoethane.

Question:

Apply IUPAC nomenclature rules, state the name of each of these molecules.

a)

▶️Answer/Explanation

Ans: 2pentene

b)

▶️Answer/Explanation

Ans: 2methylbutane

c)

▶️Answer/Explanation

Ans: 4,4dimethylpent1ene

d)

▶️Answer/Explanation

Ans: 2,3,4trimethylpentane

e)

▶️Answer/Explanation

Ans: 3,4dimethylpent1ene

Question:

Explain why the first two test tubes are discarded. What is the main component in these samples?

▶️Answer/Explanation

Ans: The first two test tubes will have a high composition of atmospheric gases that are residues of the gas found in the glass tubing prior to the start of the distillation process.

Question:

Describe the color changes observed in the tests performed on the final two test tubes.

▶️Answer/Explanation

Ans: When bromine water is added to the fifth test tube, the colour change observed will be from yellow/brown to colorless, indicating the presence of carboncarbon double bonds in the fraction.
When acidified potassium permanganate(VII) solution is added to the sixth test tube, the colour change observed will be from purple to colorless, indicating the presence of carboncarbon double
bonds in the fraction.

Question:

Predict the outcome of both of these tests on the first two test tubes that were discarded. Explain your reasoning.

▶️Answer/Explanation

Ans: The tests would show a negative result as there would be no unsaturated compounds present in the first two fractions.

Question:

Identify the largest producer of ethanol and suggest possible reasons for this.

▶️Answer/Explanation

Ans: The USA is the largest producer of ethanol. Possible reasons for this are that they have one of the largest energy demands and are one of the largest consumers of nonrenewable fossil fuels. Ethanol is used in the production of lowcarbon biofuels, a renewable resource with low carbon emissions.

Question:

Discuss why the level of production of ethanol has increased from 2007 to 2016.

▶️Answer/Explanation

Ans: Biofuel providers and the Clean Cities coalitions started in 2007 to put in place systems that simplified the process of obtaining the infrastructure to commercially sell biofuels. Known as the Low Carbon Fuel Infrastructure Investment Initiative, this project saw the growth in the number of E85 stations from one in 1996, to 95 in 2016.

Question:

China has a large population in global terms and a very large manufacturing sector, but its ethanol production is among the lowest of the nations listed. Why might that be the case? Do you think that this might change in the near future, and if so why?

▶️Answer/Explanation

Ans: China has been investing in alternative renewable energy sources such as solar power and hydroelectricity schemes. China is one of the leading investors in green technology. As the global pressure on clean energy consumption continues to increase, the policies of the Chinese government may begin to shift towards biofuels, as they are the third largest producer of sugarcane.

Question:

What natural resources might explain Brazil’s high ethanol production?

▶️Answer/Explanation

Ans: Brazil is the largest producer of sugarcane in the world. This crop is used in ethanol production.

Question:

Summarize this article for an international audience in no more than 150 words.

▶️Answer/Explanation

Ans: The summaries of individual students will vary.

Question:

What benefits has LCF13 brought to California?

▶️Answer/Explanation

Ans: The reduction in the consumption of petroleum by 39 million gallons and the reduction of carbon dioxide emissions by 187,500 tons.

Question:

Match these models (1–3) with their structural formulae (a–c) and work out their IUPAC names.

1.

▶️Answer/Explanation

Ans: c.    CH3–CH2–CH2–OH

2.

▶️Answer/Explanation

Ans: a. CH3–CH=CH2

3.

▶️Answer/Explanation

Ans: b. CH3–CH2–CH3

Question:

What evidence do we have that the combustion of fossil fuels is having a negative impact, causing global warming and climate change?

▶️Answer/Explanation

Ans: One of the main products of the combustion of fossil fuels is carbon dioxide gas. This gas is referred to as a greenhouse gas. The concentration of carbon dioxide in the atmosphere has been
increasing at an accelerated rate throughout the last century and continues today. A corresponding increase in the global mean temperature can be seen in the graphs on page 54.

Question:

In 2015, the global benchmark value of 400 parts per million for the concentration of carbon dioxide in the atmosphere was exceeded for the first time in recorded history. Can our efforts as individuals to minimize our contributions of carbon dioxide emissions make a difference on a global scale?

▶️Answer/Explanation

Ans: The efforts of individuals to decrease their contribution to carbon dioxide emissions will collectively have a significant effect on the concentration of carbon dioxide in the atmosphere and in turn help to reduce the rate of increase of the global mean temperature.

Summative assessment

Changes in carbon dioxide levels

Carbon dioxide, CO2, is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions. It is a greenhouse gas. The National Oceanic and Atmospheric Administration based in Maryland, USA derived the following information from atmospheric measurements and ice cores.

Question:

Describe the relationship between carbon dioxide concentration and time.

▶️Answer/Explanation

Ans: There is a strong positive correlation between carbon dioxide concentration and time.

Question:

Calculate the percentage increase in carbon dioxide concentration in the period 2006–2016.

▶️Answer/Explanation

Ans: Difference in CO2 (ppm) = 403 381 = 22; % increase = 22 / 381 × 100% = 5.8%

Question:

Look at the historic pattern of carbon dioxide atmospheric concentration levels. Describe the most significant aspect of present-day levels of carbon dioxide.

▶️Answer/Explanation

Ans: Prior to 1950, there was no definitive relationship between carbon dioxide concentration and time, as the levels increased and decreased with time; from 1950 to present day there is a strong, positive correlation between carbon dioxide concentration and time; from the lowest level of 180 ppm in the last 400,000 years, the present level of CO2 is twice the previous peak value / the rate of change of concentration of CO2 is far greater than ever before.

Question:

How is the global community attempting to limit the increase in carbon dioxide emissions?

▶️Answer/Explanation

Ans: Reduce the amount of burning of fossil fuels; reduce the amount of deforestation; increase the amount of electricity being produced by renewable, clean energy sources.

Question:

The alkane, hexane, C6H14, can exist as five different structural isomers. An isomer is a compound that has the same molecular formula but a different structural formula. For example, butane can exist as a straight chain or as the isomer 2-methylpropane. Both these isomers have the molecular formula C4H10.
Apply your knowledge of nomenclature rules for the naming of alkanes and determine the structure and name of the five different isomers of hexane.

▶️Answer/Explanation

Ans:

Modelling global warming

Global warming can be defined as the actual and predicted increases in temperature of the Earth’s atmosphere and oceans. The predictions are based on many types of evidence collected around the world by the scientific community.
Consider how you could use the following equipment to model global warming and the effect of the increasing amount of greenhouse gases in the atmosphere:
three digital temperature probes/software or three glass thermometers
three 1.5 litre soda bottles

rubber bungs with a hole for the temperature probes/thermometers
distilled water
antacid tablets (when these are dissolved in water they produce carbon dioxide)
high-capacity heat lamp
1 m ruler
stopwatch

Question:

Formulate a testable hypothesis.

▶️Answer/Explanation

Ans: Suitable hypothesis is suggested; hypothesis is testable; hypothesis is based on scientific reasoning.

Question:

Design an experiment to test your hypothesis. The method should include:
the independent and dependent variables, and other variables being controlled
how you plan to record your quantitative and qualitative observations.

▶️Answer/Explanation

Ans: Design should include clear statement of:

  • independent and dependent variables
  • rationale for the method and practical details, including
    • correct names of apparatus and volume
    • amounts and/or concentration of chemicals being used
  • consideration of safety, ethical and environmental issues
  • description of the stepbystep methodology for the investigation, including how variables are controlled
  • description of how qualitative observations will be recorded
  • identification of any quantitative data that will be recorded and the design of data tables to present this information

Marks awarded on a scale from zero marks for a completely inadequate design to 10 marks for an exemplary design.

Glaciers and climate change

Land ice sheets at the poles and glacial ice at high altitudes have been the subject of extensive research and monitoring as they provide evidence of accelerating global warming. Land ice and glacial ice do not contribute to sea levels in the way icebergs do. However, when melted, the water joins the planet’s oceans, resulting in rising sea levels.

Question:

This graph shows the Antarctica mass variation since 2002.

a) Interpret the presented data and describe the trend over the past 16 years.

▶️Answer/Explanation

Ans: Overall, there is a decrease in the amount (Gt) of land ice in Antarctica over the last 16 years; initially the rate of change was slow; since approximately 2010 the rate of change has increased.

b) Apart from the overall trend in the data, hypothesize why there are small upward and downward variations in the total land ice mass within a calendar year.

▶️Answer/Explanation

Ans: In the warmer months (summer), there will be a decrease in the total amount of land ice; in winter there will be an increase in the total amount of land ice.

Question:

a) Estimate the change in mass for the period 2004–2008. 

▶️Answer/Explanation

Ans: An amount in the range of 300 to 500 Gt.

b) Analyze the data and comment whether the rate of loss of mass is increasing or decreasing, in the decade following 2008. Support your argument with mathematical evidence.

▶️Answer/Explanation

Ans: Rate of loss of mass is increasing; maximum and minimum annual land ice mass are decreasing; loss in mass from 2008 to 2010 was 700 to 850 Gt over a two year period, producing a rate of change of 75 Gt year1; in the 2 year period from 2012 to 2014, the rate of loss was (15001050) / 2 = 225 Gt year1
Mathematical calculations from any of the other two year periods from 2008 to 2018 could also be used as evidence.

Question:

Explain why glacial ice, and the air bubbles trapped within it, is such an important tool in the study of climate. Include details of the various types of information scientists can ascertain from this scientific endeavour.

▶️Answer/Explanation

Ans: Glacial ice and the air bubbles trapped within it are an important tool in the study of climate because they range in age from several hundred to several hundreds of thousands of years. This means that they function as a longterm climate record; through drilling and extracting ice cores scientists can ascertain yearbyyear information about past climate; the information scientists can find include: “past atmospheric composition, temperature variations, and types of vegetation”.

Question:

What modelling can be undertaken to help scientists in their future work?

▶️Answer/Explanation

Ans: To help scientists in their future work, past eras can be reconstructed and modelling done to explain previous climate change and predict future climate patterns; global warming can be studied and explained by studying changes in glaciers, as they are very sensitive to temperature fluctuations.

Question:

How does this type of information support government and the United Nations’ actions?

▶️Answer/Explanation

Ans: By discovering and analyzing this type of information, scientists assist governments and bodies, such as the United Nations, in their planning of policies, programs and legislation; to limit future climate change and its negative effects on our planet and humankind.

Question:

The 20th century has been a time of rapid glacial retreat. What do some scientists attribute this to?

▶️Answer/Explanation

Ans: During the 20th century and before, burning fossil fuels for manufacturing, transportation and production of electricity has led to increased carbon dioxide in the atmosphere. The concentration of other gases in the atmosphere, such as methane, has also increased greatly. These greenhouse gases reflect heat energy being radiated from the surface of the earth, resulting in an increase in global temperatures. Other factors have also contributed to global warming including dust and soot from grazing, farming and manufacturing.

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