Gas Tests

Concept 2: Gas Tests

Success Criteria & Vocabulary

Criteria you should assess yourself on to be confident in your knowledge of Concept 2: Gas Tests. Vocabulary you must learn to be able to understand a question and answer it confidently.

Click this drop-down menu to see the Success Criteria.

I can describe the gas tests for hydrogen, oxygen, and carbon dioxide.
I can perform the gas tests in a group setting, safely.
I can describe my observations from the gas tests.

Click this drop-down menu to see the list of Vocabulary.

Glowing splint test: Test for oxygen gas.

Limewater: Solution that turns cloudy when carbon dioxide is bubbled through it.

Lit splint test: Test for carbon dioxide gas that uses a splint.

Pop test: Test for hydrogen gas.

Tasks

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Copy of MW Y9 Gas Test STUDENT RESOURCE.docx

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Task called 'Gas Tests'.

Concept 2: Support Notes

How to test for Oxygen Gas = Glowing Splint Test

Glowing splint test instructions:

Put a small amount of manganese dioxide (powder) into a test tube and add hydrogen peroxide (liquid). These chemicals will react together to create oxygen gas.
Hold your thumb over the test tube to collect the gas inside the test tube.
Remove the thumb quickly and place a glowing splint into the test tube.
If the splint re-ignites then it is likely the gas produced was oxygen.

Explanation:

Oxygen is needed for combustion (burning carbon from the wooden splint). If oxygen is present in a test tube, a GLOWING SPLINT re-ignites when it is held inside that tube and exposed to a high concentration of oxygen.

How to test for Hydrogen Gas = Pop Test

Pop test instructions:

Put a small piece of magnesium ribbon into a test tube with a small amount of hydrochloric acid. These chemicals will react together to create hydrogen gas.
Hold your thumb over the test tube to collect the gas inside the test tube.
Remove the thumb quickly and place a lit splint into the test tube.
If the gas makes a loud, high-pitched 'POP!' then it is likely the gas produced was hydrogen.

Explanation:

Hydrogen ignites in air. So if hydrogen is present in the test tube, a lit splint held near the mouth of the test tube will ignite with a squeaky POP!

How to test for Carbon Dioxide Gas = Lit Splint Test OR Limewater Test

Lit splint test instructions:

Put a small amount of calcium carbonate with hydrochloric acid in a test tube. These chemicals will react together to create carbon dioxide gas.
Hold your thumb over the test tube to collect the gas inside the test tube.
Remove the thumb quickly and place a lit splint into the test tube.
If the LIT SPLINT is extinguished (flame goes out), then it is likely that the gas produced was carbon dioxide.

Explanation:

Carbon dioxide displaces (removes) oxygen from the test tube. If there is no oxygen, a flame cannot keep burning, so the flame will be extinguished.

Limewater test instructions:

Put a small amount of calcium carbonate with hydrochloric acid in a boiling tube. These chemicals will react together to create carbon dioxide gas.
Place a bung with a delivery tube over the boiling tube.
Place the free end of the delivery tube into a test-tube filled with clear limewater.
Observe the gas bubbling into the limewater.
If the limewater turns cloudy, then it is likely that the gas produced is carbon dioxide.

Explanation:

Carbon dioxide is a colourless gas and LIMEWATER is a solution of calcium hydroxide in water, which is also colourless. The carbon dioxide gas reacts with the limewater and changes it into calcium carbonate, which is not soluble (cannot dissolve) in water and appears as a milky white colour.

This University Professor demonstrates what happens when hydrogen and oxygen gases react near a flame.

Clear demonstrations of how to test for oxygen and carbon dioxide. Includes the limewater test and tealight candles, which we did not do in class. No sound.

Clear demonstration of how to test for oxygen, carbon dioxide, and hydrogen. There's also information on how to test for chlorine gas, but you don't need to know about this.

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