Preparing a soluble salt | 14–16 Practicals

Summary

The video demonstrates how to safely prepare copper sulfate crystals in a laboratory setting. It explains the key steps, including heating sulfuric acid, adding copper oxide, and filtering the solution. The presenter highlights safety precautions, such as using safer heating methods and wearing protective gear. The video also discusses the chemical reactions involved, particularly the neutralization of acid by a base. By following these instructions, viewers can create well-formed copper sulfate crystals and are encouraged to experiment with making other soluble salts while prioritizing safety.

Takeaways

• 🧂 Sodium chloride, or table salt, is a well-known example of a salt and has been historically used for preserving meat, cleaning wounds, and making soap.
• 🔬 In chemistry, salts are ionic compounds formed by the neutralization of an acid by a base. Sodium chloride is just one of many types of salts.
• 🧪 The process described in the script is about preparing a different salt: copper sulfate.
• 📚 The name of the salt has two parts: the first part comes from the metal, metal oxide, or metal carbonate, while the second part comes from the acid used in the reaction.
• 🛑 Safety is crucial, and the script emphasizes using safer methods, such as warming sulfuric acid in hot water instead of using a Bunsen burner.
• 🥽 Eye protection is mandatory throughout the experiment, and precise measurements are important for success.
• ⚗️ The experiment involves neutralizing sulfuric acid with copper oxide to form copper sulfate and water, ensuring the reaction is complete by adding excess copper oxide.
• 🚰 Filtration is used to separate the copper sulfate solution from the unreacted copper oxide, with fluted filter paper to improve the process.
• 🔥 Evaporation is used to concentrate the copper sulfate solution, with precautions to avoid overheating, and anti-bumping granules are added to maintain smooth boiling.
• 💎 If left to cool slowly, well-formed copper sulfate crystals can grow overnight. The experiment can be adapted to create other salts like copper chloride or zinc sulfate.

Q & A

What is the primary component of common table salt?

The primary component of common table salt is sodium chloride.

How has salt been used by humans throughout history?

Throughout history, humans have used salt to preserve meat, clean wounds, and make soap.

In chemistry, what does the term 'salt' refer to?

In chemistry, the term 'salt' refers to a group of ionic compounds formed by the neutralization of an acid by a base.

What salt is being prepared in the experiment described in the video?

In the experiment, the salt being prepared is copper sulfate.

How are the names of salts typically structured?

The name of a salt has two parts: the first part comes from the metal, metal oxide, or metal carbonate, and the last part comes from the acid used.

Why is the method of heating sulfuric acid in hot water safer than using a Bunsen burner?

Heating sulfuric acid in hot water is safer because it minimizes the risk of knocking over hot sulfuric acid or having it spill over during the reaction due to rapid reactions.

Why is excess copper oxide used in the reaction with sulfuric acid?

Excess copper oxide is used to ensure the reaction is complete and that all of the acid has been neutralized.

How is copper sulfate separated from the unreacted copper oxide?

Copper sulfate is separated from the unreacted copper oxide by filtration, using fluted filter paper.

What are anti-bumping granules used for in the experiment?

Anti-bumping granules are used to maintain a smooth boiling action without reacting with the particles in the flask.

What should you do if the solution starts spitting or popping during evaporation?

If the solution starts spitting or popping, you should turn off the heat immediately and never let the solution boil dry.

Outlines

00:00

🔬 Understanding Salt and Introduction to Copper Sulfate Preparation

This paragraph introduces salt as sodium chloride, an essential nutrient and a widely recognized compound. The term 'salt' in chemistry is explained as a group of ionic compounds formed by neutralizing acids with bases, with sodium chloride being just one example. The focus then shifts to the preparation of copper sulfate, describing it as a common and rewarding experiment. The salt’s name derives from its metal or acid components. While the process seems straightforward, numerous incidents are reported each year, prompting the use of safer methods in the lab. The paragraph concludes with the safety step of wearing eye protection and preparing sulfuric acid to begin the experiment.

05:01

🧪 Safer Method for Heating Sulfuric Acid and Mixing Copper Oxide

This paragraph details the safer approach to heating sulfuric acid by placing the boiling tube in hot water rather than using a Bunsen burner. It walks through the process of preparing the base by measuring copper oxide powder, gradually adding it to the acid, and stirring the mixture. The importance of this method lies in minimizing risks such as spilling hot acid or rapid reactions causing spillage. The chemical reaction is described as a neutralization where copper oxide reacts with sulfuric acid to form copper sulfate and water. Excess copper oxide ensures all the acid is neutralized.

🧹 Filtering and Removing Insoluble Copper Oxide

In this section, the unreacted copper oxide is filtered out of the copper sulfate solution using fluted filter paper. The process of folding the filter paper and setting up a filtration system with a funnel and conical flask is outlined. As the copper sulfate solution filters through, the black copper oxide remains in the paper as residue. This step is crucial to separate the soluble copper sulfate from the insoluble oxide.

🔥 Evaporation and Formation of Copper Sulfate Crystals

The focus here is on evaporating the filtered solution to concentrate the copper sulfate. Anti-bumping granules are added to ensure a smooth boiling process, and the Bunsen burner is turned on. The solution must simmer gently without boiling dry, as overheating could cause spitting or popping. The hot solution is carefully poured into an evaporating dish, and a wooden spill can be used to speed up crystal formation. The paragraph highlights the result: well-formed copper sulfate crystals. However, the crystals should not be taken home due to their hazardous nature.

🔧 Experiment Variations and Safety Precautions

This final paragraph encourages viewers to apply the same steps to create other soluble salts, such as copper chloride or zinc sulfate. The emphasis is on selecting the appropriate reactants and making a thorough risk assessment before beginning any experiment. The video ends with an invitation to use additional resources for designing experiments, reminding viewers to adhere to safety guidelines and to have fun while experimenting.

Keywords

💡Sodium chloride

Sodium chloride, commonly known as table salt, is an ionic compound composed of sodium and chloride ions. In the video, it is introduced as the most recognizable salt, serving as a comparison point to other salts, such as copper sulfate. Sodium chloride is also noted for its historical uses, such as preserving food and cleaning wounds.

💡Neutralization

Neutralization is a chemical reaction between an acid and a base to form a salt and water. The video highlights this process when copper oxide reacts with sulfuric acid to form copper sulfate and water, demonstrating the creation of a soluble salt.

💡Copper sulfate

Copper sulfate is a soluble salt created through the reaction of copper oxide and sulfuric acid. It is the main product in the video, and the preparation process involves several steps, including heating, filtration, and evaporation. The video showcases the formation of copper sulfate crystals, which are often used in chemical experiments.

💡Filtration

Filtration is a technique used to separate solids from liquids. In the video, it is used to remove unreacted copper oxide from the solution of copper sulfate. The black copper oxide remains in the filter paper as the residue, while the copper sulfate solution passes through.

💡Crystallization

Crystallization refers to the process by which a solid forms from a solution. In the video, copper sulfate crystals are formed after the solution is evaporated. The use of a wooden spill is mentioned as a way to encourage crystallization by providing a rough surface for the crystals to grow.

💡Sulfuric acid

Sulfuric acid is a strong acid used in the preparation of copper sulfate. The video demonstrates a safer method of heating sulfuric acid by placing it in a hot water bath instead of directly on a bunsen burner, to minimize risks during the experiment.

💡Copper oxide

Copper oxide is a black insoluble base used in the video to react with sulfuric acid, producing copper sulfate. The video explains that an excess of copper oxide is added to ensure that all the acid is neutralized during the reaction.

💡Evaporation

Evaporation is the process of removing excess water from a solution, concentrating it to allow crystallization. In the video, the copper sulfate solution is gently heated to evaporate water, which is a crucial step before the copper sulfate crystals can form.

💡Anti-bumping granules

Anti-bumping granules are small, inert particles added to a solution during heating to prevent violent boiling or 'bumping.' In the video, they are used when evaporating the copper sulfate solution to ensure a smooth, controlled boiling process.

💡Safety precautions

Safety precautions refer to measures taken to prevent accidents during experiments. The video emphasizes wearing eye protection, using safe heating methods, and handling chemicals like sulfuric acid carefully. It also reminds viewers not to take copper sulfate crystals home, as they are hazardous.

Highlights

Sodium chloride, commonly known as salt, is a key nutrient and has been used throughout history for preserving food, cleaning wounds, and making soap.

In chemistry, the term 'salt' refers to a group of ionic compounds formed by the neutralization of an acid by a base, with sodium chloride being just one example.

The name of a salt has two parts: the first comes from the metal, metal oxide, or metal carbonate, while the second part comes from the acid.

This experiment involves preparing copper sulfate, a soluble salt, through a practical method that emphasizes safety and correct procedures.

Heating sulfuric acid using hot water from a kettle is a safer method compared to using a Bunsen burner, as it reduces the risk of spills and accidents.

The reaction between copper oxide and sulfuric acid produces copper sulfate and water in a neutralization reaction.

Excess copper oxide ensures complete neutralization of the acid and a full reaction, leaving some unreacted copper oxide visible after the reaction.

Fluted filter paper is used to separate the copper sulfate from unreacted copper oxide, with the copper oxide acting as residue since it is insoluble.

Anti-bumping granules are added to ensure smooth boiling during evaporation, preventing rapid or uneven boiling.

The solution should be heated gently for two minutes, avoiding any spitting or popping noises, and never allowed to boil dry.

Crystals of copper sulfate can be formed by pouring the solution into an evaporating dish and letting it cool slowly.

Using a wooden spill inside the evaporating dish can speed up crystal formation by providing a rough surface.

Copper sulfate crystals can be hazardous, so it's important not to take them home despite their appealing appearance.

The experiment provides an excellent opportunity for students to practice making other soluble salts, such as copper chloride or zinc sulfate.

Safety precautions, like using student safety sheets and performing risk assessments, are emphasized throughout the process to ensure a safe and successful experiment.

Transcripts

The product we all instantly recognise and  know as salt is sodium chloride. Sodium  

chloride is the source of sodium, a key  nutrient in our diet. Throughout history,  

humans have been using salt to preserve  meat, clean wounds and make soap.

In chemistry, the term salt refers  to a group of ionic compounds  

formed by the neutralisation of an acid by  a base. Sodium chloride is just one example  

of a salt. Today I'm going to be preparing  a different soluble salt: copper sulfate.

The name of the salt has two parts: the  first part of the name comes from the metal,  

metal oxide or metal carbonate;  the last part of the name  

comes from the acid. This is a very rewarding  practical - especially if you get well-formed  

crystals at the end - this would explain  why this is such a popular experiment.

On first appearance, preparing a soluble crystal  in the lab is a straightforward practical. After  

all, all you need to do is follow a method.  However, every year a high number of incidents  

and accidents are reported. Here I'm going to show  you how to prepare some copper sulfate crystals.  

I'm going to point out where  things could potentially go wrong  

and where we're going to be using a safer method  than the standard one seen in the textbooks.  

But don't worry, we're going to follow  all the same steps, just in a safer way.

First things first, eye protection on! I'm  now going to measure out 15 centimetres-cubed  

of sulfuric acid using a measuring  cylinder and pour it into a boiling tube.

Next, I'm going to half fill this beaker  with hot water for my ready-boiled kettle.  

Now, I will gently stand the boiling tube in  the hot water for about two to three minutes.

While I wait, I will prepare the base. I  need to measure out between 1.8 and 2 g of  

black copper oxide powder using a measuring boat.  Now add half of the copper oxide to the acid...

agitate gently...

then place the boiling tube back in  the water. This method of heating the  

sulfuric acid is safer than heating it on a  bunsen burner, because it minimises the risk,  

of both knocking over hot sulfuric  acid when adding the copper oxide,  

and the very hot sulfuric acid spilling over the  beaker when the copper oxide is added, due to a  

rapid reaction taking place. When the reaction  subsides add the rest of the copper oxide.

You'll notice that some of the black copper  oxide powder remains. Let's take a moment to  

think about what has happened here. Remember a  salt has formed by the neutralisation of an acid  

by a base. Copper oxide has reacted with sulfuric  acid to form copper sulfate and water. This is a  

neutralisation reaction because the negative  sulfate ions have reacted with the positive  

copper ions to form copper sulfate and water.  We added an excess of copper oxide to ensure  

that the reaction has completed and that  all of the acid has been neutralised.

In this next step, we're going to  separate the product (copper sulfate)  

from the unreacted reactant (copper oxide)  using filtration. We will be using fluted  

filter paper. To do this we will start  by folding some filter paper in half...

opening it up and folding it in half again...

opening it up, half again...

and once more in half again.

We will then start  making indents between these segments.

Here is one I made earlier!

I have already placed a filter  funnel in a 100 centimetre-cubed conical flask  

and I will place my fluted  filter paper into my funnel.  

Now I'm going to pour my copper  sulfate into the filter paper.

Be careful when pouring that none of the  copper sulfate solution goes over the edge.  

The copper sulfate solution is now dripping  through the filter paper, down the filter  

funnel into the conical flask. And inside the  filter paper we can see some black copper oxide.  

The copper oxide is insoluble so cannot go through  the filter paper: this is called the residue.

Now we need to remove excess water by evaporation to  make a concentrated solution of copper sulfate.  

Before we start, I need to add two  to three anti-bumping granules.  

These will help maintain a smooth boiling action  

but do not react with any of  the particles in the flask.

Now, I'm going to place my  conical flask on my tripod  

and turn the bunsen burner  to the blue roaring flame.

It's important that you let this gently simmer  for two minutes only. If you hear any spitting  

or popping noises you must turn the heat off  immediately and never let the solution boil dry.

I'm going to use a heatproof glove to pour the hot  solution into the evaporating dish or petri dish.  

Pour it carefully.

If the crystals don't form  quickly we can use a wooden spill  

and place it inside the evaporating  basin. This will speed up the reaction  

as it creates a rough surface  for the crystals to form on.

As you can see, we have produced  some amazing copper sulfate crystals.  

If you leave them to cool slowly overnight  you could even end up with crystals  

that look like this. It might  be tempting to take them home  

but it's important that you don't because  they do carry three hazard warning symbols.

Now that you know how to make copper sulfate  crystals, starting with an insoluble oxide,  

why not use the same sequence of steps to  make other soluble salts? You will need to  

start by working out which reactants to use  and don't forget to use the student safety  

sheets to make a risk assessment before you  start. Why not use the additional resources  

attached to this video to design a plan to  make copper chloride or zinc sulfate crystals?

Thank you for watching, have  fun with your experiments!

Inspiring your teaching and learning.