50% of Your Exam Is Problem Solving, the Following

Problem Solving in National 5 Chemistry – Part 1

50% of your exam is problem solving, the following

booklet is designed to teach you the skills you require in this section of the exam.

ContentsPage

Section 1: Graphs

1 a) Drawing Bar Graphs2

1 b) Drawing Line Graphs5

1 c) Interpreting graphs/ Questions on graphs7

Section 2: Tables

2 a) Tables from passages14

2 b) Tables from pie charts and vice versa15

2c) Flow charts/diagrams17

NB

This problem solving booklet has been adapted from Standard Grade so remember you will not have a credit and general questions in your paper.

National 5 pupils may find credit level questions the most useful.

Problem solving Section 1: Drawing and interpreting Graphs

1 a) Drawing Bar Graphs

Bar charts can be used to represent a set of results (which are often presented in a table) These are usually found in General Level Exams.

Look at the following example and follow the rules.

e.g.

Draw a Bar chart of the Melting points for the following elements.

Rule 1: When drawing a bar chart you first of all put the factor which is under your control( i.e. the variable you are changing) along the horizontal axis e.g. Elements and the factor which you are measuring( i.e. the outcome) on the vertical axis. e.g. Melting Point REMEMBERING any units!!!!

Rule 2: You must choose a suitable scale for the vertical axis. It must be a continuous scale and your graph should take up at least half of the available space.

Rule 3: Plot your bars accurately using a ruler

e.g. The bar for Sulphur should be drawn up to 113, phosphorus up to 44 etc…….

Now try the examples on the next page

Examples-Drawing Bar Graphs

1) The weights of different metals used by a factory in one week are recorded in the table below:

Draw a bar graph to illustrate these results

2) A third year pupil added 1cm3 of various tissues to Hydrogen peroxide and then measured the volume of oxygen produced in 3 mins. Draw a bar graph of these results.

Now you are getting comfortable drawing bar charts let’s try some from General past paper questions.

3) Oil spilt at sea can cause damage to the environment. This table shows the sources of oil pollution of the sea.

Draw a bar chart to show this information

(2)

4) Teeth which have decayed can be repaired with dental fillings. Dental fillings are made by mixing powdered metals with liquid mercury to make dental amalgam. The powdered metals used are silver(70%), tin(26%0, copper(3%), and zinc(1%)

Draw a bar graph to show the percentages of the powdered metals in the amalgam.

(2)

5) The table shows some of the uses of poly(ethane) Draw a bar chart to show this information.

6) The following table shows the percentage of each fraction obtained from a barrel of crude oil. Draw this as a bar graph.

7) The pie chart shows the composition of the earth’s crust. Present this information as bar chart.

8) The pH values of some solutions are shown in the table. Draw a bar graph to show this information

Problem solving Section 1: Drawing and interpreting Graphs

1 b) Drawing Line Graphs

Line graphs can be used to represent a set of results (which are often presented in a table) These are usually found in Credit Level Exams.

Look at the following example and follow the rules.

e.g.

A science teacher held a beaker over a burning candle. She then noted the time taken for the candle to stop burning. Draw a line graph from the teacher’s results.

Rule 1: When drawing a line graph you first of all put the factor which is under your control( i.e. the variable you are changing) along the horizontal axis e.g. Volume of beaker and the factor which you are measuring( i.e. the outcome) on the vertical axis. e.g. Time REMEMBERING any units!!!!

Rule 2: You must choose suitable scales for both the vertical and horizontal axis. It must be a continuous scale (e.g. 10,20,30, 40 etc) and your graph should take up at least half of the available space.

Rule 3: Plot your points accurately

e.g. The cross for 200 cm3 should be drawn up to 12s

Rule 4: Draw a best fit line. It is not a dot to dot!!! You may use a ruler for a straight line but you must draw a curve yourself.

Your graph should look like this

Now try the examples on the next page

Examples- Drawing Line Graphs

(please keep your graphs for these questions as they will be used in section 1c- interpreting graphs)

1) A third year pupil carried out an investigation to find out if the temperature effected how quickly the enzyme amylase breaks down starch. Draw a line graph of these results.

2) A material used in the building industry was tested by a scientist to see how quickly it soaked up water. The results she obtained are shown below. Draw a line graph of these results.

Now you are getting comfortable drawing line graphs let’s try some from Credit past paper questions.

3. Acid’s are shown to contain Hydrogen ions using a Hoffman voltmeter. The volume of Hydrogen gas produced over a period of time was measured during the electrolysis of dilute sulphuric acid. The results are shown in the table. Draw a line graph of these results.

4. The table shows the relationship between solubility of sulphur dioxide in water and the temperature of the water.

Draw a line graph of solubility against temperature.

5. Sodium carbonate reacts with Hydrochloric acid to form carbon dioxide. Brian measured the volume of carbon dioxide given off over a period of time and recorded his results.

Draw a line graph of the results.

6. Hydrogen can be produced in the laboratory by adding excess hydrochloric acid to lumps of zinc. The reaction stops when all the zinc is used up. The volume of gas produced over a period of time was measured and the results shown in the table. Draw a line graph of the results.

Problem solving Section 1: Drawing and interpreting Graphs

1 c) Interpreting graphs/ Questions on graphs

At credit level you are often asked to use the line graph you have just drawn to answer questions. The following examples for you to try are using the graphs you have just drawn in section 1b. You do not have to redraw them unless you haven’t completed section 1b.

Worked example Type 1

Acid’s are shown to contain Hydrogen ions using a Hoffman voltmeter. The volume of Hydrogen gas produced over a period of time was measured during the electrolysis of dilute sulphuric acid. The results are shown in the table. Draw a line graph of these results.

Your graph from section 1b should look like this.

Predict the volume of Hydrogen gas which would be produced during the first 10mins?

Answer- Draw a vertical line on your graph at 10mins until it reaches your line graph, then draw a horizontal line across to the scale and read off the volume as accurately as possible.

Volume = cm3

You may also be asked to comment on the relationship between the two variables e.g. The volume of the Hydrogen gas increases as the time increases. (REMEMBER TO MENTION BOTH VARIABLES AND SHOW DIRECTION!!!)

Now try the examples on the following page

Examples- Interpreting Line Graphs

1) The table shows the relationship between solubility of sulphur dioxide in water and the temperature of the water.

Use your line graph of solubility against temperature from Q4 in section 1b.

State the relationship between the solubility of sulphur dioxide in water and the temperature of the water.

2. Sodium carbonate reacts with Hydrochloric acid to form carbon dioxide. Brian measured the volume of carbon dioxide given off over a period of time and recorded his results.

Use your line graph from Q5 in 1b.

Suggest a value for the volume of carbon dioxide collected during the first 20s.

3. Hydrogen can be produced in the laboratory by adding excess hydrochloric acid to lumps of zinc. The reaction stops when all the zinc is used up. The volume of gas produced over a period of time was measured and the results shown in the table. Use your line graph from Q6 in 1b.

Estimate the time in seconds, for 40 cm3 of Hydrogen to be produced.

4. A third year pupil carried out an investigation to find out if the temperature effected how quickly the enzyme amylase breaks down starch. Use your line graph from Q1 in 1b.

State the relationship between the temperature and the units of sugar produced.

5. A material used in the building industry was tested by a scientist to see how quickly it soaked up water. The results she obtained are shown below.

Use your line graph from Q2 in 1b.

Predict the volume of water that you would expect to be soaked up after 5 hours?

Problem solving Section 1: Drawing and interpreting Graphs

1 c) MORE Interpreting graphs and Questions on graphs

You may also be asked to interpret graphs that you have not drawn yourself. Try the following examples. These are all from credit past papers.

Q1) The graph below shows the different percentage yields of ammonia which can be obtained under different conditions in the ammonia plant. What is the relationship between the percentage yield of ammonia and the temperature at constant pressure?

Q2) The graph shows the ionisation energy values for the 1st 20 elements.

a) Describe the trend in ionisation energy going from Lithium to Neon.

b) Describe the trend in ionisation energy going down a group

Q3) Water can exist in three different states: solid liquid and gas. The state depends on the temperature and the pressure. The diagram below shown these relationships.

a) In which state would water exist at 15oC and 0.007 atmospheres?

b) Solid water at 0.004 atmospheres is allowed to warm up. The pressure is kept constant. At what temperature would the solid water change into a gas?

Q4) The spike graph shows the relative size of some atoms.

a) Describe what happens to the atom size going down a group.

b) Describe the trend in atom size going from lithium to fluorine

Q5) The graph shows the relationship between the growth of the human population and the amount of ammonia produced by industry.

Why has the increase in world population led to an increase in ammonia production.

6) Over 2 million tonnes of sulphuric acid are made in the UK each year. The main reaction involves the conversion of sulphur dioxide to sulphur trioxide using a catalyst. The graph shows the percentage of sulphur dioxide which can be converted to sulphur trioxide at different temperatures.

Describe the trend shown by the graph.

7)Sam added manganese dioxide to hydrogen peroxide solution and measured the volume of oxygen produced. Her result for two experiments at different temperatures are shown below.

a) What volume of oxygen was collected in experiment A?

b) The same volume and concentration of hydrogen peroxide was used in both experiments A and B. How can you tell this from the graph?

c) At the start experiment B was faster than experiment A. How can you tell this from the graph.

Q8) A mass spectrometer is an instrument that can be used to measure the percentage of isotopes in a sample of an element. When a sample of chlorine is passed through a mass spectrometer the following graph is obtained. Each spike on the graph shows the presence of an isotopes.

a) the following graph obtained for a sample of lithium.

(i) How many isotopes are present in the sample of lithium.

(ii) Using the information in the graph calculate the relative atomic mass of lithium.

Problem solving Section 2: Drawing Tables

2 a) Tables from passages

Another problem solving skill is to be able to read a passage, select the important information and present it in a table with suitable headings. These are usually found in General Level Exams.

Look at the following example and follow the tips.

e.g.

Copper is a metal with useful properties. It is a good heat conductor. This makes it useful for making saucepans. Because it is not very reactive with water it is used for water pipes in our homes. It is used in electrical wiring because it is a good electrical conductor. It is also used in jewellery as it is malleable.

Tip 1: Read the passage, highlighting any important information

Tip2: Decide on appropriate headings

Tip3: Draw your table using a ruler

Tip 4: Put all the information in your table

When you read the passage you should notice the following important information:

Copper is a metal with useful properties. It is a good heat conductor. This makes it useful for making saucepans. Because it is not very reactive with water it is used for water pipes in our homes. It is used in electrical wiring because it is a good electrical conductor. It is also used in jewellery as it is malleable.

Your table should look like this:

Now try the examples on the following page

2 a) Examples of Tables from passages

1) Aluminium is a metal with a large number of useful properties. It is a good heat conductor. This makes it useful for making saucepans. Because it is resistant to corrosion it is used to make window and door frames. It has a low density which is one reason for its use in overhead power cables. One of the reasons it is used for cooking foil is that it is malleable.

Present the above information in a table with suitable headings.

2) PVC has many uses because of its different properties. Its strength makes it ideal for bottles. It is used for protective clothing because of its water resistance and, its chemical resistance makes it ideal for food containers. It is used for plugs and cables because it is an electrical insulator.

Present the information shown above as a table with suitable headings

3) Alcoholic drinks contain different percentages of alcohol. Beers contain 5% but some ciders are stronger at 7.5%. Red wine contains 12%, but fortified wines contain 18%. Whiskey is much stronger at 40% alcohol.

Present the above information in a table with suitable headings.

4) Copper can be mixed with other metals to produce alloys for different uses.

Aluminium is added to copper to make an alloy suitable for aircraft bodies. Coins are made from a hard wearing alloy which contains copper and nickel. Musical instruments can be made from an alloy of copper and zinc. If tin is added to copper the alloy can be used to make ship’s propellers.

Present this information in a table with suitable headings.

2 b) Tables from pie charts and vice versa

You may also be asked to draw tables from pie charts or a pie chart from a table.

Try the following examples.

1) The pie chart shows the uses of sulphuric acid. Present the information in the form of a table with suitable headings.

2) The pie chart shows the uses of ammonia. Present the information in the form of a table with suitable headings.

3)

The mass of some of the air pollutants that enter the air in Britain each year are shown in the table below. Present the following information as a pie chart.

(Hint: it may help to work out the percentages first as the total is not 100!!!)

2 c) Flow Charts

You may be given information in a passage and asked to complete a flow chart or you may be given a completed flow chart and be asked questions from it. These can be at general or credit level. Although you may not have seen the chemistry in the examples before there will be enough information in the question for you to complete it. (Circles are usually for chemicals and rectangles for the processes/reactions. But not always, particularly at credit level.) Try the following general level examples.

1) Ammonium nitrate is made by the reaction of ammonia with nitric acid.

Ammonia is made by passing a mixture of nitrogen and hydrogen through a catalyst chamber. Unreacted nitrogen and hydrogen are removed and returned to the catalyst chamber. The ammonia gas then enters a reaction vessel in which ammonium nitrate is produced.