Agree Learning Outcomes: Topic: C4.2 lesson 1 Testing for Gases Spec link: OCR (Kerboodle) C4.2.1 / C3.1.6 Collins C4.7 / C3.5 Time: 70 min Recorded Assessment: : Self evaluation tasks Review: Knowledge about ‘Formula of gases’ Present New Knowledge: Powerpoint slides Videos Agree Learning Outcomes: Recall tests for the four common gases (oxygen, hydrogen, carbon dioxide, chlorine) Identify the four common gases using the tests Explain why limewater can be used to test for carbon dioxide Apply To Demonstrate: Hands on practical session to demonstrate understanding Quiz and Plenary task Construct Meaning: Observe demonstrations and discuss to construct meaning

Match up the words with their descriptions Bell Match up the words with their descriptions The substance being broken down Test for Oxygen Positive electrode Test for Hydrogen Makes a ‘popping’ noise when lit Electrolyte Splitting a substance using electricity Anode Relights a glowing splint Cathode Negative electrode Anion Positive ion Cation Negative ion Electrolysis

Match up the words with their descriptions The substance being broken down Test for Oxygen Positive electrode Test for Hydrogen Makes a ‘popping’ noise when lit Electrolyte Splitting a substance using electricity Anode Relights a glowing splint Cathode Negative electrode Anion Positive ion Cation Negative ion Electrolysis

LO Learning objectives: Describe the tests to identify the four common gases (Oxygen, Hydrogen, Carbon dioxide and Chlorine) Identify the four common gases using these tests Explain why limewater can be used for testing CO2.

Learning Outcomes: Distinguish gases using chemical tests. LO Learning Outcomes: Distinguish gases using chemical tests. Describe how each test works. Recognise that carbon dioxide reacts with lime water to form an insoluble carbonate.

Video link for testing gases CM Video link for testing gases https://www.youtube.com/watch?v=LiAvDpl5aJA https://www.youtube.com/watch?v=uE_XSjGIDw4

Test for Hydrogen gas CM The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a ‘pop’ sound. The basis for this test is that hydrogen is reacting rapidly as a fuel by burning in oxygen. The product is water. Demo or Student Practical: Take 20 ml of 1M HCl in a test tube Add 2cm strip of Mg ribbon to the test tube with the HCl Invert an empty tube to collect the Hydrogen gas liberated during the reaction by the downward displacement of air Use a bung to prevent escape of gas Remove bung and immediately bring a burning splint to hear a popping sound to test the presence of Hydrogen gas. Note: Teacher’s discretion to decide whether to show a demo or have a class practical. Teachers to order equipment accordingly. Other alternatives : Demo only - Bursting of Hydrogen Balloon

Test for Oxygen gas CM Demo: Wear Eye Protection The test for oxygen uses a glowing splint inserted into a test tube of the gas. The glowing splint relights in oxygen. Demo: Wear Eye Protection In the 250ml Buchner Flask add 0.1g manganese (IV) oxide powder or 1g of granules Fill a 250ml measuring cylinder with water to collect the gas, this allows you to flush out the apparatus before collecting gas in boiling tubes. Ensure the delivery tube goes from the flask to under the Beehive. The beehive should be covered in water. Add about 20 ml of 20 vol Hydrogen Peroxide to the buchner flask Invert a boiling tube filled with water above the beehive shelf whilst still under water to collect the gas. Hydrogen peroxide breaks down to release Oxygen gas which is collected by the downward displacement of water Gently remove the boiling tube full of Oxygen gas ensuring the top has a bung to prevent the loss of Oxygen. Bring a glowing splint and introduce it within the boiling tube to see it getting re-lighted Note: Demo only. For demonstrating downward displacement of water and collection of Oxygen gas. Hydrogen peroxide breaks down to release Oxygen gas which is collected by the downward displacement of water (water in the inverted gas jar is pushed down while Oxygen gets collected on top). Manganese dioxide simply speeds up the process without reacting.

Test for Chlorine gas CM Demo: The test for chlorine uses litmus paper. When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white. Chlorine can also be bubbled into water and tested with litmus paper, which bleaches. Demo: Take a test tube half filled with freshly prepared Chlorine water solution Dip indicator paper and see it getting bleached. Note: Demo only. Teacher to specify on order list requesting Chlorine solution

Test for Carbon dioxide gas CM Test for Carbon dioxide gas The test for carbon dioxide uses an aqueous solution of calcium hydroxide (which is often called ‘limewater’). When carbon dioxide is shaken with or bubbled through limewater the limewater turns milky (it looks cloudy). What is happening with this test? Limewater is calcium hydroxide. When carbon dioxide is passed through limewater, the product formed is calcium carbonate. This white chalky substance (calcium carbonate) gives a milky appearance to the solution. Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

Test for Carbon dioxide - Student Practical ATD Test for Carbon dioxide - Student Practical Take about 20ml 1M HCl solution in one boiling tube/conical flask Add about 20ml of limewater to another boiling tube Add a spatula full of Calcium Carbonate or 2 to 3 medium sized marble chips to the HCl solution and seal the end with the bung on the delivery tube. Insert the other open end of the delivery tube into the boiling tube containing limewater solution Observe the limewater go from colourless to cloudy/milky Note: Takes care of Lesson objective 3.

Plenary: Match the images with the names of the listed gases 1 3 2 4 Chlorine Oxygen Hydrogen Carbon dioxide

Revision Link and Task list ATD Revision Link and Task list http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/chemicalre actions/preparinggasesrev1.shtml Tasks: Use the revision link above to explain the three ‘Methods of collecting gases’. (use pages 1 and 2 of the link) Copy the table and complete the blank cells given on page 3 of the link Write detailed notes for testing Oxygen, Hydrogen, Carbon dioxide and Chlorine. (page 4 of the link) Take the bitesize test Extension: Collins quiz at the end of topic 4.7 Depending on the time left after the practicals, the task list can be split as partly Class work and partly home work.

Answers to Collins Quiz 1. Definitely oxygen; 2. Definitely chlorine; 3. Possibly carbon dioxide; other gases will also put out a lighted splint; 4. Definitely carbon dioxide; 5. Possibly hydrogen; other gases (e.g. methane) react explosively with oxygen, but only hydrogen burns with a squeaky pop