Knox Academy Science Department

S2 Science

Our Material WorldPart 4

1 Properties of GasesThe ability of natural gas to react very quickly and so cause an explosion is known as a property of that gas.

A property of a substance tells us about the chemical or physical nature of that substance and we often summarise the information in a table.

Notes: Copy the following information

The properties of a substance tells us about the Chemical or Physical nature of the substance. For example the boiling point of natural gas is –162oC. Boiling point temperature is a property.

Activity: Read the following paragraph and use the information to copy and complete the table.

Properties of Chlorine

Chlorine is a choking green gas, which boils at –35oC and freezes at –101oC. In water treatment plants it is used to make water fit for drinking as it dissolves in the water and kills bacteria and other harmful organisms. If too much is added the water tastes unpleasant.

State at room temperatureColourSmellMelting point (oC)Boiling point (oC)Solubility

Properties of Hydrogen

In Our Material world 3 you reacted metals with acid. When you did this a gas was given off. The gas was hydrogen. We now want to find out the properties of hydrogen.

Notes: Copy the diagram and the table below.

Properties of Hydrogen

Property ObservationState

ColourEffect of lighted splintHeavier or lighter than air.

Collecting a Gas over Water

You are going to set up the experiment as shown in the diagram you have just drawn. Your teacher will help with this.

Collect: 3 test tubes hydrochloric acid (2mol/l)1 boiling tube zinc pieces1 test tube rack1 delivery tube1 plastic tub3 stoppers

Activity: 1. Half fill the tub with water.2. Stand the boiling tube in a test tube rack and

then add about 3 pieces of the granulated zinc to the tube.

3. Pour about 3 cm depth of the hydrochloric acid into the boiling tube and put the delivery tube on the top.

4. To get rid of air, allow quite a few bubbles to bubble through the water in the tub.5. Collect and stopper 3 test tubes of the hydrogen gas.6. Test the gas in one test tube with a lighted splint.

Heavier or lighter than air?7. To do this, with the stoppers out hold one of the test tubes of hydrogen the right

Tub of WaterMagnesium Pieces

Delivery TubeTest Tube

Test Tube

Hydrochloric Acid

way up and the other upside down for 1 minute.

8. Test both with a lighted splint.

Can you now tell which one still contained hydrogen?Does this mean it is heavier or lighter than air?

Notes: Complete the table you have drawn.

2 Testing Gases Oxygen, Nitrogen and Carbon dioxide

Demonstration: Your teacher will show you how to collect a test tube of gas from a large bottle of gas and how to do the glowing splint and the burning splint tests.

Notes: Copy the table below

Property Oxygen Nitrogen

Carbondioxide

ColourSmellLimewater testBurning splintGlowing splint

Collect: 2 test tubes 2 stopperstest tube rack

Activity: 1. Collect 2 test tubes of any of the gases2. Look at the colour of the gas in the

first tube then take the stopper off and gently waft the gas towards your nose.

3. Write the results in the table4. The limewater test;

Remove the stopper and put 2cm of limewater into the second test tube. Put the stopper back on and gently shake the test tube.

5. Record your results in the table.6. Collect another 2 test tubes of the

same gas.7. Burning splint test:

Light a splint, remove the stopper from 1 tube and put the splint into the test tube.

8. Record your results in the table.9. The glowing splint test:

Light a splint then blow it out, leaving the embers glowing. With the second tube, remove the stopper and put the glowing splint into the test tube.

10. Record the results in the table.11. Repeat steps 1 to 10 for the other 2

gases.

Notes: Answer the following questions

1. Which gases put out a burning splint?2. Which gas had an effect on limewater?3. Which gas had what effect on a glowing

splint?4. Copy and Complete

The best way to identify oxygen gas is that it will __________ a _________ splint.The best way to identify carbon dioxide gas is that it will turn _________cloudy.

3 Identifying an Unknown Gas

In the last lesson you learned some facts about how to identify some gases. Use this information to complete the following, using the missing words given below.

The missing words are: cloudy, oxygen, colourless, burning, carbon dioxide, relights, glowing, nitrogen, lime, blowing

Some words are used more than once!

Three common gases found in air are oxygen, nitrogen and carbon dioxide. All three gases are _________ and have no smell so we need chemical tests to identify them.

The glowing splint test involves lighting a splint and then _________ it out and putting the _________ splint into the test tube of gas to see if it _________. If it does the gas is _________ .

The _________water test involves shaking the gas in a test tube with a little limewater and looking for the limewater to go from clear and colourless to _________. If it does the gas is _________.

As we have just described there are good tests for _________ and _________ but not for _________.Nitrogen is usually identified by the fact that it will put out a _________ splint but does not turn _________water cloudy.

Notes: Copy the table below

Gas Jar Glowing Splint

Limewater Name of Gas

ABCD

In this experiment you must decide whether the gas is carbon dioxide, nitrogen or oxygen. It must be one of these three.

Collect: 2 test tubes2 stopperstest tube rack

Activity: 1. Collect 2 test tubes of one of the gases as you were shown last day.

2. Carry out the glowing splint test and record your result in the table.

3. Carry out the limewater test and record your results in the table.

4. Work out which gas it is and write this in the table.

5. Repeat the experiment to identify the other gases.

4 Preparing and Collecting a GasA Very Important Gas

You are going to collect a gas over water, as you did in lesson 1. You will then test it to find out which of the gases you have already met, it is.

Delivery TubeTest

TubeTest Tube

Hydrogen peroxide

Manganese(IV) oxide

Water

Collect: 1 boiling tube hydrogen peroxide (10vol)2 test tubes manganese(IV) oxide2 stoppers1 plastic tub1 delivery tube1 test tube rack

Activity: 1. Half fill the tub with water.2. Stand the boiling tube in a test tube rack and

then add about a quarter spatula of manganese(IV) oxide to the tube.

3. Pour about 3 cm depth of the hydrogen peroxide into the boiling tube and put the delivery tube on the top.

4. To get rid of air, allow quite a few bubbles to bubble through the water in the tub.

5. Collect and stopper 2 test tubes of the gas.6. Test the gas in the first test tube with limewater.

7. Test the gas in the other test tube with a glowing splint.

Notes: Copy the diagram above and write a sentence or two to describe the experiment thenCopy and complete the following:

The limewater test showed that the gas was/ was not __________.The glowing splint test showed that the gas was/ was not __________.

Gases Puzzle:

The names of some common gases have been spelled out in code. The first one is neon, can you work out the names of the other gases?

1 6 2 7 3 8 4 9 5 10 11

5 Gases in the AirAir is a mixture of gases. It is a mixture of nitrogen and oxygen.We know that we need air to keep us alive, in particular we need the oxygen, which is in the air to survive but how much of the air is oxygen?

Notes: Copy this table

Gas Mixture Glowing splint testAir100% oxygen60% oxygen20% oxygen

Collect: 1 test tube1 stopper

Activity: 1. Around the room there are 4 large bottles containing air, 100% oxygen, 60% oxygen and 20% oxygen. One at a time, collect a test tube of the gas in the bottle.

2. Test the gas sample with a glowing splint and record in your table whether it relit or not.

Discuss: Which sample behaved most like air?

Notes: Copy and complete the following

The mixture which behaved most like ordinary air was _____ % oxygen.Air contains _____% oxygen.

Other Gases

In dry air there is approximately 79% nitrogen, 20% oxygen and 1% of all the other gases.

Notes: Using the title Gases in the Air present this information as a bar graph. Stick the bar graph into your lab book.

Carbon Dioxide

You probably know that all living creatures breathe out carbon dioxide but we have not yet mentioned it in air. It is part of the ‘other gases’ above. Can we test air for carbon dioxide?

Collect: 1 test tube limewater1 stopper

Activity: 1. Put 1cm of limewater into the test tube, stopper it and with your finger over the stopper shake it for a short time.

2. Has the limewater gone cloudy white? 3. Your teacher will let you see some

limewater left open to the air for a few days.

4. What do you see on the surface and what do you think has caused it?

Notes: Copy and complete

Ordinary air does not turn limewater cloudy. However, limewater does go _________ if it is exposed to air for a few days.

6 Trace Gases and Problem SolvingWater in the Air

There is a convenient test to identify if air contains water. This is called the Cobalt Chloride Paper Test.

Your teacher will show you samples of this paper in wet air and in dry air.

Cobalt Cobalt chloride chloride paper paper

Dry Air

Wet Air

Discuss: What do you notice about the 2 samples?

Notes: Copy the labelled diagrams and copy and complete the following:

When cobalt chloride paper is in dry air it is coloured _________.When cobalt chloride paper is in wet air it is coloured _________.

Percentage of Trace Gases

The actual quantity of water in the air changes greatly from day to day and from place to place.Temperature also causes changes with air at 30oC being able to hold three times as much water as air at 10oC.

Because of this the % of gases in the air is normally given without including the water. This is called dry air. The following table shows how the 1% of trace gases is split up.

% of Trace Gases in the AirGas Percentageargon 0.93neon 0.002helium 0.0005carbon dioxide 0.03krypton 0.00011xenon 0.00001others Tiny amount

Notes: 1. Why is water not included in the trace gases table?

2.The more there is of a gas the more abundant we say it is. List the 5 most abundant gases in order. Make up a title for your list.

3. Which trace gas is there most of in air?

Separation of the Gases in Air

Many of the gases in air are useful on their own but how do we get them on their own and not as part of a mixture?

A common way to do this relies on the different boiling points of the gases. The air is cooled down until all the gases in the air have changed into a liquid mixture (liquefied). This is then warmed up and the lowest boiling gas boils off first. This is then recondensed into a pure liquid.

Notes: Copy and complete

Word Bank : recondensed liquefied mixture

Separation of the gases in Air

Air is a _________. To get individual gases air is first _________ by cooling and then it is warmed up. The separated gases are then __________ to make liquid pure gases.

Discussion: Look at the following table and discuss the answers to the questions with your lab partner. When you are in agreement write the answers in your jotter.

Melting and Boiling points of Gases in the Air

Gas Melting Point / oC

Boiling Point / oC

Nitrogen -210 -196Oxygen -218 -183Argon -198 -186Carbon dioxide

Sublimes at –79*

Neon -249 -246Helium -270 -269Krypton -157 -152*Sublimes means going straight from the solid to gas states

1. As liquid air was being cooled, which substance would stop being a gas at the highest temperature?

2. Which substance has the smallest difference between its melting and boiling point?

3. Which substance will be last to condense as the air is cooled down?

4. Draw the particle pictures to represent krypton being warmed from –160 to –150oC.

5. Draw a large thermometer which goes from minus 200 degrees Celsius to zero degrees Celsius and then mark alongside the boiling point temperatures of the gases in the air. Give your diagram a title.

7. Burning in Air

Many materials burn in air. When a material burns it is undergoing a chemical reaction.

Burning is also known as combustion.

Discuss: Which gas present in the air is required before an object will burn?

Energy is also released during burning. Can you think of three materials that can be burned to produce energy?

Notes: Copy the aim, diagram and table that follow:

Aim: To find out if altering the volume of air around a candle affects how long the candle burns for.

candle

beaker

mat

Size of beaker (ml)

Time the candle burns for (seconds)Trial 1 Trial 2 Average

600400250100

Collect: a set of beakers candleheatproof matstopwatch

Experiment: 1. Place the candle in the middle of aheatproof mat.

2. Light the candle.3. Cover the candle with the 600 ml

beaker and start the stopwatch.4. Stop the stopwatch when the candle

goes out. Write down the time in seconds in the column marked trial 1.

5. Wash the beaker and dry it with a paper towel.

6. Repeat the experiment and enter the result in your table under trial 2.

7. Now repeat steps 2 to 6 for the other beakers.

Collect: a piece of graph paper.

Notes: Draw a line graph of size of beaker (x-axis) against average time (y-axis).

Answer the following questions using sentences, in your jotter.

1. Why were the experiments repeated and an average time calculated?

2. As the volume of air around the candle increased, what happened to the time the candle burned for?

3. Why does the volume of air affect the time for burning?

Copy and complete the sentence below:

When a candle burns, ________________ gas from the air is used up.

8. Oxygen in AirOxygen is required for burning. We find oxygen present in air.

Discuss: How much oxygen is present in air?

How could you prove the % of oxygen present in air?

Notes: Copy the diagram below

Collect: Boiling tube with a scaleCandle

250 ml beakerCork

Experiment: 1. Half fill a 250 ml beaker with water.2. Float a candle on the water.3. Light the candle and cover it with the

boiling tube.4. Observe what happens.

Notes: Answer the following questions usingsentences in your jotter.

1. What happens to the lit candle?2. What happens to the level of water in

the boiling tube as the candle burns?3. Which gas from the air has been used

up during burning?

250 ml beaker

water

boiling tube

cork

candle

4. What % of air is this gas (approximately)

Discuss: Using the same equipment, design an experiment to show the exact % of oxygen present in a sample of fresh air compared to exhaled air.

Notes: Write a plan of your proposed experiment. Remember to include sections on:

AimHypothesisEquipmentMethodResults table

To ensure a fair test ensure you repeat your experiment and take an average.

After you have checked your method with your teacher, carry out your experiment and write a conclusion based on your results.

9. Burning CarbonIn the last lesson we found out that air contains 20% oxygen. Oxygen is needed for a fuel to burn.

Discuss: When a material containing carbon burns, whatcompound will be produced?

What is the chemical test for this compound?

Notes: Copy the table below:

Weight (g)Mass before HeatingMass after HeatingChange in mass

Collect: Metal tongs lump of carbonBunsen burnerHeatproof matGlass tube

Experiment: 1. Find the mass of the carbon lump andrecord it in your table.

2. Hold the carbon lump gently in a pair of metal tongs and heat it in a Bunsen flame until it is red hot.

3. Remove the carbon lump from the Bunsen flame and blow gently on it for 10 minutes using the glass tube.

4. Leave the carbon lump to cool on the heatproof mat for 5 minutes.

5. Find the mass of the carbon lump and record it in your table.

6. Calculate the change in mass of the carbon lump.

Notes: Answer the following questions:

1. What happened to the mass of the carbon lump during the experiment?

2. Why does the mass of the carbon lump change?

3. What compound could have been produced when carbon combined with oxygen?

4. Write a word equation for the reaction you have observed. Under each chemical write which state it is in.

Discuss: How could you show the product of burning carbon in air?

Which chemical test could you use to identify the product of burning carbon in air?

Using a similar approach to the experiment you carried out above, design an experiment to identify the product of burning carbon in air.

HINT: The gas produced is heavier than air.

Notes: Write a plan of your proposed experiment. Remember to include sections on:

AimHypothesisEquipmentMethodResults table

After you have checked your method with your teacher, carry out your experiment. To ensure a fair test ensure you pool results with other groups in your class. Write a conclusion based on your class results.

10.Burning Iron

Fuels are not the only things that burn. Some metals can burn in air. When a metal burns it combines with oxygen to produce a compound called a metal oxide.

Discuss: Which metals have you seen burning?

What signs are there that a chemical reaction has taken place when a metal burns?

Notes: Copy the table below:

Weight (g)Mass before Heating (can + wool)Mass after Heating (can + wool)Change in mass

Collect: Metal can steel woolHeatproof matBunsen burnerGlass tube

Experiment: 1. Find the mass of the metal can and steel wool. Record the value in your table.

2. Set fire to the steel wool by heating with a Bunsen burner from above. Keep the steel wool alight by blowing strongly through the glass tube onto the steel wool.

3. Once the steel wool has stopped burning (after about 10 minutes) allow it to cool for 5 minutes.

4. Find the mass of the metal can and steel wool. Record the value in your table.

5. Calculate the change in mass of the steel wool.

Notes: Answer the following questions:

1. What happened to the mass of the steel wool during the experiment?

2. Why does the mass of the steel wool change?

3. What compound could have been produced when the iron in the steel combined with oxygen?

4. Write a word equation for the reaction you have observed.

Copy and complete the following:

Steel contains mainly ______ .

_________ in air + ________

________ ________

Iron oxide is a _________ and has the mass of the ______ and ______. This explains why the steel __________ in mass when it burned.

Extension: Use the information in the table to answer the questions that follow.

Compound Name

Formula Elements present

magnesium oxide MgO magnesium + oxygen

calcium chloride CaCl2 calcium + chlorineiron oxide FeO iron + oxygen

sodium iodide NaI sodium + iodinecopper sulphide CuS copper + sulphur

1. Name the elements with the following symbols

a. Mg b. Fec. O d. Cae. Cl f. Cug. Na h. S

2. If two elements combine to make a compound, thecompound’s name will end with the letters “-ide”.

Name the following compounds.

a. iron and oxygenb. iron and iodinec. copper and chlorined. sodium and sulphure. CaSf. MgI2g. FeSh. NaCl

11. Fire Fighting

Fuels are chemicals we burn to release energy. In previous lessons we have shown that oxygen is required for a fuel to burn. Fire fighters use information regarding how a fire burns to work out how best to put out a fire.

Notes: Watch the video Fire. Then copy the following.

Fire fighters extinguish fires by removing one factor from the fire triangle. The fire triangle shows us the three things that must be present before a fuel will burn.

If one factor from the triangle is removed, then the fire will go out.

Collect: boiling tube 1 mol/l hydrochloric acidcandle in holderheatproof mat calcium carbonate powdermeasuring cylinder detergentstopper with delivery tube

You will now build your own fire extinguisher and use it to extinguish a burning candle.

oxygen

fuel

heat

Experiment: 1. Measure 20 ml of hydrochloric acid and pour it into your boiling tube.

2. Add 5 drops of detergent and mix gently.

3. Place your candle on a heatproof mat and light it.

4. Measure 3 spatulas of calcium carbonate powder onto a piece of scrap paper.

5. Assemble all your pieces of equipment together.

6. Add the calcium carbonate powder to the boiling tube and quickly place the stopper with its delivery tube in the neck of the boiling tube.

7. Direct the open end of the delivery tube at the burning candle to extinguish the flames.

Notes: Draw a labelled diagram of your experiment.

Answer the following questions.

1. What is produced during the reaction between the calcium carbonate and acid?

2. Which factors from the fire triangle are affected by your fire extinguisher?

12.Making MetalsWe use many objects made from a variety of different metals. Most metals are found in the ground combined with other elements. Before we can make a metal object we have to extract a pure sample of the metal from its compound.

The compounds found in the earth that we can use to extract pure metals from are known as ores.

Discuss: Which objects do you use daily that are made of metal?

Which metals are used to make these objects?

Notes: Write the sub-heading Extracting Copper

Collect: test tube mixture of carbon and clamp stand copper oxideBunsen burnerheat-proof mat

HEAT

Experiment: 1. Place a test tube in a clamp stand at a45 angle.

2. Add 2 spatula measures of the carbon and copper oxide mixture to the test tube.

3. Heat the test tube gently using a half open Bunsen flame for 2 minutes.

4. Open the air hole fully and roast the test tube until you observe signs of a chemical reaction.

5. Switch off the Bunsen and allow the equipment to cool before touching.

Notes: Answer the following questions using sentences in your jotter.

1. What evidence was there that a chemical reaction had occurred?

2. Which metal was produced during the reaction?

3. Suggest three uses for the metal you extracted from its ore.

Extracting IronVideo: Iron is a commonly used metal, it can be

extracted from its ore in a special type of oven known as a blast furnace.

Watch the short video showing you how iron is extracted from its ore.

Collect: A blast furnace diagram and stick it into your jotter.

Notes: Copy the heading Extracting Iron.

Use the information you saw during the video and page 46 of Starting Science book 2 to help you complete the labels for your diagram.

Write a word equation to show the overall reaction that occurs in a blast furnace.

Why is limestone added to a blast furnace?

Extension: Read page 46 of Starting Science Book 2 and answer questions 1 to 5 using sentences in your jotter.

13. What makes iron rust?Many things we use in our daily lives contain iron. If we leave iron open to the air it will rust. Rusting iron can cost a lot of money to replace.

In this lesson you are going to investigate what makes iron rust.

Discuss: Look at the examples of iron objects that have become rusted.

What do you think has caused the iron to rust?

Is rusting a chemical reaction? Why?

Notes: Copy the diagram and the table that follows.

Discuss: Look at the experiment set up a few days ago.

Carefully examine the surface of each nail. Which nail shows signs of rusting?

What must be present before the iron nail can rust?

What is the chemical name for rust?

Notes: Copy and complete the following

tube oxygen present?

water present?

rusting?

ABC

BB CA

water boiledwater

oildryingagent

When iron rusts it undergoes a ___________ change.

Iron changes from being present as an ____________ to forming a compound. The chemical name for rust is ________ ________.

A word equation for iron rusting would be:

iron + oxygen ______ _______

For iron to rust, _______ and ______ must be present with the iron.

Preventing Rusting

Iron objects are strong and cheap to make. Scientists have developed ways of protecting iron from oxygen and water. If we protect the iron from oxygen and water we can stop rusting from happening.

Discuss: Watch the video on rusting.

Can you think of an example of an iron object that is not rusty, even although it is left exposed to water and oxygen for a long period of time?

What is the surface of the iron object coated with to stop it from rusting?

Look at the set of nails coated with different materials.

Why has each nail not rusted?

Extension: Read page 47 of Starting Science Book 2.

Notes: Answer questions 1 to 5 using sentences in your jotter.

14.Speeding up rustingSome objects rust faster than others. Have you ever noticed that iron objects beside the sea rust faster than inland?

In this lesson you will investigate why iron objects rust at different speeds.

Discuss: Why could a car rust faster beside the sea,compared to inland?

Can you think of any other examples of environmental factors that could make iron objects rust faster?

Scientists use universal indicator to investigate the pH of a solution. Scientists can use a special rust indicator to investigate the rate of rusting. Rust indicator changes colour when rusting is happening.

yellow (no rusting) blue (rusting)

You will use rust indicator to investigate the effect of salt solution and acid on rusting.

Notes: Copy the diagram below.

AA

distilledwater

B

acid

C

salty water

Collect: 3 boiling tubes 3 iron nailsBoiling tube rack distilled watermeasuring cylinder salty water

acidrust indicator

Experiment: 1. Label 3 test tubes A, B and C.2. Measure 5 cm3 of distilled water into

tube A.3. Measure 5 cm3 of salty water into

tube B.4. Measure 5 cm3 of acid into tube C.5. Place an iron nail in each tube.6. Leave tubes for 10 minutes.7. Carefully add 5 drops of rust indicator

to each tube.8. Colour in your diagram to show the

colour present in each tube.

Discuss: Which tube(s) showed the most blue colour?

Which tube(s) showed the most rusting?

Why should you wash your car more regularly if you stay beside the sea?

What effect does the salt spread on the roads have on the undersides of our cars?

What could cause the presence of acid in the environment?

Notes: Copy the following.

Rust indicator changes colour from yellow to blue when rusting happens. The darker the blue colour the more rusting has happened.

Salty water and acid increase the amount of rusting that takes place compared to water on its own.

Pollution from factories and cars releases gases that can cause acid rain. Acid rain can cause iron objects to rust faster.

Extension: Read page 98 of Starting Science Book 1.

Notes: Answer questions 1 to 4 using sentences in your jotter.