Reactions of group 1 metals

Summary

This 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

00:00

🔥 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.

05:03

🔬 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.

10:05

💧 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.

Keywords

💡Alkaline Metals

Alkaline metals refer to the elements in Group 1 of the periodic table, which include lithium, sodium, and potassium. These metals are highly reactive due to having a single electron in their outermost shell, making them eager to lose this electron to achieve a stable electron configuration. In the video, alkaline metals are shown reacting with air, water, and chlorine, demonstrating their reactivity. The script mentions storing these metals in oil to prevent reactions with moisture in the air, highlighting their sensitivity to environmental conditions.

💡Reactivity

Reactivity in chemistry refers to the tendency of a substance to undergo a chemical reaction. The video script illustrates the reactivity of alkaline metals by showing their reactions when heated in air, exposed to chlorine, and when reacting with water. The trend in reactivity is a key theme, with potassium being the most reactive and thus producing the most dramatic reactions, which are saved for last for maximum impact.

💡Physical Properties

Physical properties are characteristics that can be observed or measured without changing the substance's chemical identity. For alkaline metals, physical properties such as conductivity and density are demonstrated. The script mentions the shiny silver surface of lithium, which tarnishes over time, and the light weight of lithium, which is passed around for students to feel, indicating its low density.

💡Conductivity

Conductivity is the ability of a material to conduct an electric current. Alkaline metals are known for their high electrical conductivity due to the availability of their valence electrons. The script describes using a circuit tester to demonstrate that lithium conducts electricity, showcasing this property in a practical experiment.

💡Tarnish

Tarnish refers to the dulling or discoloration of a metal surface due to oxidation or other chemical reactions. In the context of the video, the shiny silver surface of alkaline metals is mentioned to tarnish over time when exposed to air, indicating a reaction with oxygen that forms an oxide layer on the metal's surface.

💡Heating in Air

Heating in air is a method used to observe the reaction of metals with oxygen at elevated temperatures. The script describes the process of heating small pieces of alkaline metals to observe their reactions with the oxygen in the air, leading to the formation of metal oxides and other compounds. This experiment is used to compare the reactivity of lithium, sodium, and potassium.

💡Moist Indicator Paper

Moist indicator paper is a type of pH indicator used to detect the presence of moisture or certain chemicals. In the script, it is used to test the residue left after the metals have reacted with air, indicating the formation of metal oxides. The change in color of the indicator paper provides a visual confirmation of the chemical reaction.

💡Chlorine

Chlorine is a halogen element that is highly reactive and is stored in a gas jar in the script. The video demonstrates the reaction of alkaline metals with chlorine, which is a test of the metals' reactivity with a non-metal. The script describes the setup for this experiment, including ensuring a small opening on the gas jar to contain the chlorine gas.

💡Water Reaction

The water reaction is a demonstration of the metals' reactivity with water, which is a common test for alkaline metals. The script shows lithium reacting with water to produce hydrogen gas, which is then tested with a lit taper to produce a 'squeaky pop' sound, indicating the presence of hydrogen.

💡Rubidium and Caesium

Rubidium and caesium are alkaline metals that are heavier than lithium, sodium, and potassium. The script suggests extending the experiment to include predictions about these metals, indicating a progression in the periodic table towards elements with even greater reactivity. This is an opportunity to discuss trends within the alkali metal group.

💡Periodic Table

The periodic table is a tabular arrangement of chemical elements by atomic number, electron configuration, and recurring chemical properties. The script mentions following the periodic table order for the experiments, which not only provides a logical structure to the demonstrations but also builds up to the most reactive metal, potassium, at the end.

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.