Class 10 Science Chapter 2 Acids Bases and Salts

You all learned about acids, bases, and salt in class  7. So, as you already know that all the acids are sour in taste and bases are bitter in taste. Also, acids change the blue litmus paper into red, and bases change the red litmus paper to blue. In Class 10 Science Chapter 2 Acids Bases and Salts we will learn more about acid, bases, and salts.

However, in your previous classes, you also learned about litmus and how it shows the difference between acids and bases. So, in this chapter, we are going to learn more about acids, bases, and salts. Also, in this chapter, there are some good activities from which you can check in your surroundings what things are acids and what are bases.

So, acids are very common in our food such as lime, oranges, etc which contain citric and ascorbic acid which is also known as Vitamin C. Even our body has its own kind of acid i.e. Hydrochloric acid. Likewise, some of the food is basic in nature like avocado, Bitter gourd, etc.

Class 10 Science Chapter 2 Acids Bases and Salts

Here in this section, we will look at a quick summary of acid bases and Salts from the previous class. So, these points will help you remember some important things which in turn will help you understand this chapter more efficiently.

• As we already know acids are sour and bases are bitter in taste.
• Also, bases are soapy when we touch them, so this is another way of knowing about the bases.
• Acid can turn blue litmus to red and bases can turn red litmus to blue.
• There are some substances that are not acidic or basic in nature, those substances are known as neutral.
• We use indicators to know about the substance which are acidic or which are basic in nature.
• Also, we know that acid and base neutralize each other and form a salt. So, by this, we can say that Salt is either acidic or basic, or neutral in nature.

Now in class 10 science chapter 2 acids bases and salts, we will see some more properties of these three. But first, let’s understand some basics about them.

What are Acids?

It is known as a chemical that donates protons or hydrogen ions or accepts electrons. It has a pH of less than 7. It turns blue litmus to red. It is sour in taste such as vinegar. Also, its structure is sticky in nature.

What are Bases?

It is known as a chemical species that gives away electrons and accepts protons. It has a pH of greater than 7. It turns red litmus to blue. It is bitter in taste such as baking soda. Also, its structure is soapy or slippery in nature.

What is a Litmus?

It is basically a solution that is purple in color, it is extracted from lichen. It is commonly used as an indicator, which we use to find out the nature of the particular thing i.e. acid or base.

Class 10 Science Chapter 2 Acids Bases and Salts

Our memory about the physical properties of acid bases and salts is refreshed now.  So, we are going to learn about the chemical properties of acids and bases and their reaction with metals in this section.

# Chemical properties of Acids and Bases

First, let’s see the properties of Acids:

• A liquid solution of acids can conduct an electric current. As it contains both strong and weak electrolytes.
• They have a sour taste.
• They change the color of some of the indicators like blue litmus turns red and phenolphthalein turns colorless.
• It reacts with active metals like sodium, calcium, etc.
• They react with base and form a compound named salt and water. When we add the base to the acid, the acid is neutralized.

In class 10 science chapter 2 acids bases and salts we will also learn about the properties of bases. So, now let’s see the properties of the base:

• Its liquid solution is also electrolyte in nature and can conduct electric current.
• They have a bitter taste in them and are found less frequently in foods as compared to acids.
• They change the color of the indicators like red litmus to blue and phenolphthalein to pink.
• These are less common as food but they are mainly present in many households products like soaps, etc.
• They don’t react with metals as acids do.

# Acid and Base react with each other

The reaction which occurs when acid and base react with each other is also known as neutralization reaction. When we combine both of them they give us the product i.e. salt and water. See the equation below:

Equation:

Here:

• Na → Sodium
• HCl → Hydrochloric acid
• NaOH → Sodium Hydroxide
• NaCl → Sodium Chloride (Common Salt)
• H2O → Water

Class 10 Science Chapter 2 Acids Bases and Salts

In this section of Class 10 Science Chapter 2 Acids Bases and Salts, we are going to discuss the common things in all of the acids and bases. Also, about how strong are acid and base solution.

# Common things in all of the Acids and Bases

Similarities are given below:

First, we talk about Acids:

• All acids generate hydrogen gas while reacting with metals.
• All acids turn blue litmus paper into the red.
• All of the acids have a pH of less than 7.
• All acids release hydrogen when we dissolve them in water.

Now, let’s talk about the Bases:

• All Bases turn red litmus paper into blue.
• All of the bases have a pH of more than 7.
• All Base has a bitter taste and soapy texture.
• All Bases release hydroxide ions when we dissolve them in the water.
• Some metals like Zinc and Aluminium reacts with a base to form hydrogen gas and salt, see the equation below:

Equation with Zinc:

Equation with Aluminium:

# How strong are Acid or Base Solutions?

Can we measure the concentration amount of acids and bases? Can we judge how strong a particular acid or base is? What if there is a way to measure the concentration of acid and base by only using 1 indicator or we can say by universal indicator.

Actually, there is a way, by using the most famous universal indicator which can give results about all the particular acid and base, known as pH scale. Huh!!, What is a pH scale? you ask.

pH: pH stands for “potenz” in german which means power. It contains numbers in them from 0 to 14. 0 will be most acidic and 14 will be most basic in nature. In general terms, pH indicates the concentration of hydrogen ions in the solution.

If a solution has a pH value of 7 it means it’s neutral and has no acid nor base in it such as water (H2O). But if a solution has a pH value of less than 7, then it means it has acid in it and acidic in nature. Also, if the pH value of a solution is greater than 7, then it means it has a base in it and it is basic in nature.

Class 10 Science Chapter 2 Acids Bases and Salts

In this section of Class 10 Science Chapter 2 Acids Bases and Salts, we are going to talk about the importance of pH in everyday life.

# Importance of pH scale in our life

Here we include all the importance of the pH scale.

1. pH effect in plants and animals

All the living organisms are able to survive if there is only a small change in pH value i.e. between 7 to 7.8. Although, their pH value can be changed if the pH value of rainwater becomes less than 5.6. By this, if the soil becomes too acidic we add quicklime, slaked lime, or chalk. Also, if the soil becomes more basic or we can say alkaline in nature then we have to add manure or compost.

2. pH effect in the digestive system

Our digestive system already has an acid in it i.e. Hydrochloric acid. As the human body has a physiological reaction that takes place on pH 7 to 7.8. If you ever feel indigestion or pain and irritation then it is because your digestive system produces more than usual HCl which has a pH value of 1 to 3. To resolve this problem we can use antacids like milk of magnesia and baking soda.

3. pH effect on tooth decay

This happens when the pH of the mouth becomes lower than 5.5. As we all know our teeth is the hardest substance in our body so, it doesn’t dissolve in water but can corrode due to low pH. You often hear that do not eat sweets in excess amount. It is because sweets produce acids in the mouth and not only sweets but all kind of food produces it. Which affects the tooth. To prevent this brush your teeth daily after eating too.

There is much more importance of pH in our everyday life. But these are the most common which everyone has faced in his life.

Class 10 Science Chapter 2 Acids Bases and Salts

In this section of Class 10 Science Chapter 2 Acids Bases and Salts, we are going to discuss salts.

# What is Salt?

Salts are an ionic substance that is formed when acid and base react with each other and neutralize each other. Also, salts have no electric charge on them.

# Family of Salts

There are mainly 3 families of salts all are given below:

1. Chloride Family: In this family name is given by an acidic radical of salt. Its example is Sodium Chloride (NaCl) and Calcium Chloride (CaCl2).

2. Calcium Family: This family has a name due to basic radical. Its example is Calcium Chloride (CaCl2) and Calcium Sulphate (CaSO4).

3. Zinch Family: Its name is based on basic radical. Its examples are Zinc Chloride (ZnCl2) and Zinc Sulphate (ZnSO4).

# pH value of Salts

• A Neutral salt has a pH value of 7.
• A salt that is acidic in nature has a pH value of less than 7.
• A salt that is basic in nature has a pH value of more than 7.

# Chemicals obtains from Common Salts

There are some chemicals which we can obtain from the common salt

1. Sodium Hydroxide
Equation:

Here:

• Sodium Hydroxide → NaOH

2. Bleaching Powder

Equation:

Here:

• Bleaching Powder → Ca(OCl)₂

3. Baking Soda

Equation:

Here:

• Baking Soda → NaHCO₃

4. Washing Soda

Equation:

Here:

• Washing Soda → Na₂CO₃.10H₂O

# Plaster of Paris (POP)

When we heat gypsum to 373K, then it losses water molecules that are present in it. And then it becomes another element known as calcium sulfate hemihydrate (CaSO₄.½H₂O). This is generally known as Plaster of Paris.

These are the substance mainly used by doctors and in hospitals while treating bone fractures. Although, POP is a white powder when we mix it with some water it becomes gypsum and gives solid. Its equation is given below:

Equation:

Class 10 Science Chapter 2 Acids Bases and Salts
1 Marker	2 questions
5 Marker	1 question
Total questions	3
Total marks	7
Class 10 Science Chapter 2 Acids Bases and Salts Blueprint 2021-22

According to the table, this chapter contains 2 questions of 1 mark each and one question of 5 marks. Please note that this marking scheme may vary in board exams.

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