Reactions of group 1 metals
Summary
TLDRThis educational demonstration explores the reactivity and physical properties of alkali metals—lithium, sodium, and potassium—through various reactions. The video showcases their heating in air, interaction with chlorine, and response to water, highlighting increasing reactivity. It emphasizes safety, visibility for observation, and the use of tools like circuit testers to demonstrate conductivity. The metals' tarnishing rates and the spectacular potassium reaction are key points, with practical tips for conducting the experiments safely and effectively.
Takeaways
- 🔥 Lithium, sodium, and potassium are alkali metals that react differently when heated in air, chlorine, and water, demonstrating their reactivity trends.
- 👀 Visibility can be a challenge during these experiments due to the small amounts of metal used, suggesting the use of a video camera and projector for better observation.
- 📝 It's recommended to have observers, such as students, draw up a table to record observations and predictions, enhancing learning through active engagement.
- 🎥 Performing the reactions of potassium last is advised for maximum impact, as they are the most dramatic and visually impressive.
- 🔩 Alkaline metals are stored in oil to prevent reactions with moisture, highlighting the importance of proper storage and handling.
- ✂️ Cutting the metals demonstrates their physical properties, with lithium being difficult to cut, indicating its hardness compared to sodium and potassium.
- 💡 The metals' ability to conduct electricity is showcased, with a circuit tester used to illustrate this property.
- 🔥 When heated, the metals react with air, showing different rates of tarnishing and melting, with potassium reacting the quickest.
- 🌈 The use of moist indicator paper tests the presence of sodium oxide and other residues, providing a method to confirm the reactions' products.
- 💧 The metals' reactions with water are also demonstrated, with lithium producing a squeaky pop sound when reacting, indicating the release of hydrogen gas.
Q & A
What are the three alkali metals demonstrated in the script?
-The three alkali metals demonstrated in the script are lithium, sodium, and potassium.
Why are alkali metals stored in oil?
-Alkali metals are stored in oil to protect them from reacting with moist air, which could cause them to tarnish or even ignite.
What physical property is demonstrated by cutting a piece of lithium?
-The physical property of lithium demonstrated by cutting is its hardness, as it is quite difficult to cut, indicating its solid nature.
How does the shiny silver surface of lithium change over time?
-The shiny silver surface of lithium tarnishes over time when exposed to air.
What is the purpose of using a circuit tester with lithium?
-The circuit tester is used to demonstrate the electrical conductivity of lithium, a physical property of alkali metals.
Why is it recommended to dry off the oil from the metal before heating?
-The oil must be dried off before heating to ensure that only the metal reacts with the air, and to prevent the oil from interfering with the experiment or causing a fire.
What is the significance of the blue cone of a Bunsen flame?
-The blue cone of a Bunsen flame represents the hottest part of the flame, which is used to heat the metal for the experiment.
How does the tarnishing rate of potassium compare to lithium and sodium?
-Potassium tarnishes much quicker in air than lithium and sodium, indicating a higher reactivity.
What is the observable color change when potassium is heated in air?
-When potassium is heated in air, an observable purple flame can be seen, which is indicative of the potassium's reaction with oxygen.
What is the purpose of using moist indicator paper in the experiment?
-Moist indicator paper is used to test the presence of moisture in the residue left after the metal has reacted with air, helping to identify the formation of metal oxides.
How is the reaction of lithium with water demonstrated in the script?
-The reaction of lithium with water is demonstrated by adding a small piece of lithium to tap water in a boiling tube, followed by adding an indicator to confirm the production of hydrogen gas.
Outlines
🔥 Introduction to Alkaline Metals' Reactivity
This paragraph introduces an experimental demonstration focusing on the reactivity of alkaline metals—lithium, sodium, and potassium—when heated in air, exposed to chlorine, and reacted with water. It emphasizes the importance of visibility for observing the small amounts of metals used and suggests using a video camera and projector for better viewing. The paragraph also mentions the physical properties of these metals, such as their light weight and electrical conductivity, and recommends creating a table for students to record observations and predictions. The demonstration starts with heating the metals in air, showing the process of cutting the metals and their initial reactions, including the tarnishing of their surfaces. Special precautions regarding the storage of these metals in oil to prevent reactions with moist air are highlighted.
🔬 Observations of Alkaline Metals' Reactions
The second paragraph continues the demonstration by detailing the reactions of lithium, sodium, and potassium when heated in air. It describes the process of cutting and preparing the metals, noting the ease of cutting potassium compared to lithium. The paragraph also discusses the metals' quick tarnishing when exposed to air and their ability to conduct electricity, demonstrated using a circuit tester. The reactions are conducted using a Bunsen burner flame, with the metals melting and reacting with the air, producing oxides that can be tested with moist indicator paper. The paragraph concludes with the setup for a chlorine reaction, including the preparation of chlorine gas and the safety measures to ensure the gas does not escape during the experiment.
💧 Reactions of Alkaline Metals with Water
The third paragraph describes the reactions of lithium, sodium, and potassium with water. It outlines the steps for conducting these reactions, including drying the metals with a paper towel before introducing them to water. The paragraph explains the addition of an indicator to confirm the production of hydrogen gas during the reaction. A specific test is mentioned, where a small piece of lithium is added to tap water and the gas is ignited with a lighted taper, resulting in a 'squeaky pop' sound, indicating the presence of hydrogen. This paragraph focuses on the observable phenomena and the experimental procedures for safely conducting these reactions with water.
Mindmap
Keywords
💡Alkaline Metals
💡Reactivity
💡Physical Properties
💡Conductivity
💡Tarnish
💡Heating in Air
💡Moist Indicator Paper
💡Chlorine
💡Water Reaction
💡Rubidium and Caesium
💡Periodic Table
Highlights
Demonstration of reactions of lithium, sodium, and potassium with air, chlorine, and water to show similarities and reactivity trends.
Use of video camera and projector recommended for visibility of small metal samples.
Suggestion to have the audience draw up a table to record observations and predictions.
Order of experiments from lithium to potassium for maximum impact.
Physical properties of alkaline metals demonstrated through cutting and handling.
Storage of alkaline metals in oil to prevent reaction with moist air.
Lithium's difficulty in cutting and its shiny silver surface that tarnishes over time.
Lithium's ability to conduct electricity demonstrated with a circuit tester.
Light weight of lithium pieces passed around for audience perception.
Safety precautions advised for handling alkaline metals.
Heating metals in air requires drying off oil and using a roaring Bunsen flame.
Testing of metal residue with moist indicator paper to identify oxides.
Sodium's quicker tarnishing compared to lithium when exposed to air.
Potassium's ease of cutting and its rapid tarnishing in air.
Conductivity of potassium demonstrated with a circuit tester.
Melting and burning of potassium with a Bunsen flame showing a purple flame.
Preparation of chlorine in a gas jar for metal reactions.
Reaction of lithium with water producing hydrogen gas confirmed with a pop test.
Transcripts
This demonstration shows the reactions of lithium, sodium and potassium
on heating in air, in chlorine and with water
and also shows some of their physical properties. We hope to show the similarities
between the metals and also their trend in reactivity.
Visibility can be a problem when doing these sets of
experiments due to the very small amounts of metal that you'll be using.
If you have access to a video camera and projector
this could work very well for your students to be able to see the small detail.
There are a lot of observations to be made by the audience
and it is probably worthwhile getting them to draw up a table
like this one to fill in while they watch. This could be extended to include room for
predictions about rubidium and caesium.
For greatest impact do the reactions of potassium last as they are the most spectacular.
Periodic table order seems logical
and builds to the most spectacular at the end.
The first experiment is going to be heating in air.
In preparation we need to cut some of the metal and this is an ideal opportunity
to show some of the physical properties. First of all
we should point out that all the alkaline metals that we are using are stored in oil.
Take some of the metal out of the container using some tweezers and place on a tile.
We're going to cut a small amount of the metal off this large chunk.
As you can see with the lithium, it's quite difficult to cut.
There we go. And you can see clearly the shiny silver surface. Over time this this does tarnish.
I'm going to put this big chunk of lithium back in the container.
A second physical property that can be demonstrated
is the ability of the metal, in this case lithium, to conduct electricity.
I'm going to cut a small piece of lithium. There you go.
Pick up the piece of lithium and drop it on to petri dish.
Pass it around the class so that the audience can get an impression of how light in weight it is.
Warn students not to touch the metal,
taping the lid on to the petri dish if necessary. Next, you will need to cut
a 3 mm cube piece of metal in order to heat in air.
Before we heat in air, you need to dry off the oil from the metal using some paper tissue.
We no longer recommend using hexane to dissolve the oil
because there have been fires when washing up due to some residues.
Place the little bit of metal on a flat brick.
When heating the metal, you need to use a roaring bunsen flame
and position the metal at the top of the blue cone which is the hottest part.
You can test the white residue with moist indicator paper.
Next we're going to look at reaction with sodium metal.
Again, indicate to your class that sodium is stored in oil
to protect it from reacting with moist air.
We need to cut a piece of sodium off this large piece.
You can see the lovely shiny silver surface
that tarnishes much quicker than the lithium in air.
I'll just put this back in here.
We can use a circuit tester to show that it conducts electricity.
Cut off a small piece ready to heat in air.
Dry off the piece of sodium
and place it on a brick ready to heat.
Again, with a roaring bunsen flame, you can see it melting
and reacting with the air.
We can again test the residue of sodium oxide with some moist indicator paper.
This is the reaction of potassium in air.
Again, the potassium is stored under oil and we need to cut a piece off.
You can see it is much easier to cut. This is much softer.
There's the shiny silver surface which tarnishes
quickly in air, much quicker than with the lithium and sodium.
Again, we can use the circuit tester to show clearly that it conducts electricity.
And then we need to cut off a small piece to heat it in air.
It very quickly melts.
You can just see a purple flame.
For this you will need some previously prepared chlorine stored in a gas jar
sealed with Vaseline. You should make sure that
there is a green colour of the gas in the gas jar.
You should also make sure
that the opening of the gas jar is smaller
than the brick so you don't lose the chlorine out
when you put it over the burning piece of metal.
Heat the metal up until it's burning
You can see that one goes much quicker.
Lithium, dry it off with a paper towel.
Put it in the water
When the reaction's finished you can add some indicator.
Add some indicator
To confirm the gas is indeed hydrogen
add a very small piece of clean lithium to a little tap water
in a boiling tube. Wait for a few seconds
and pop the gas with a lighted taper. A squeaky pop.
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