Lesson 3

Hey people! I had a great today during science lessons! I hope you guys too!:D Well, today, I've learnt about new topics! They are acids and bases! But I will talking about acids this week!:D Basically, I have summarize the important points about this topic! I tried to make this topic as interesting as possible but do approach me if you have any doubts!:D Enjoy!:))

Before I start....

What is acid?

Is it something salty? Is it sweet? What is that??

Basically, acid is --> a substance which produces hydrogen ions as the only positive ions when it is dissolved in water.

Acid have 4 properties. They are :

1. They have a sour taste.
2. Dissolve in water to form colourless solutions which conduct electricity.
3. Acids turn blue litmus paper red
4. Reacts and metals, carbonates and alkalines.

Here are some examples of the strong acids :

1. Hydrochloric acid
2. Nitric acid
3. Sulfate acid

Here are some examples of the weak acids:

1. Ethanoic acid
2. Malic acid
3. Tartaric acid
4. Citric acid

So how do we know the strength of the acids?

-->The strength of an acid depends on its degree of dissociation / ionisation in water to form hydrogen ions.

Therefore,

STRONG ACIDS = 1)acids that ionise / dissociate completely in water to produce hydrogen ions

2)There are no molecules left.

3)The properties and reactions of acids are due to these hydrogen ions.

Weak Acids = 1)ionises / dissociates incompletely / partially in water to produce few hydrogen ions

Concentration

-amount of a solute dissolved in a unit volume of the solution

So what does it mean by a concentrated acid?

-->one in which the proportion of acid to water is very high.

On the other hand, diluted acid is...

-->one in which the proportion of acid to water is low.

Wait a moment, HAVE YOU EVER WONDER WHAT'S THE IMPORTANCE OF WATER FOR ACIDITY?

1. Pure acids exist as molecules instead of ions.
2. Pure acids do not behave as acids as the properties of acids are due to the presence of hydrogen ions.
3. When acids are mixed with water, ionization of acids occurs, and hydrogen ions are produced. Therefore, acids can only behave as acids when they are dissolved in water.

As mentioned above, one of the properties of acids is that they react with metals, carbonates and bases. Here are the 3 formulas :

For metal :

Acid + Metal --> Salt + hydrogen

Oberservations :

1) Effervescence observed. Colourless, odourless gas evolved which extinguished a lighted wooden splint with a ‘pop’ sound.

2)Grey solid reduced in size (when in excess). Grey solid dissolves to form a colourless solution

3)Heat liberated.

For carbonates :

Acid + Carbonates --> Salt + Carbon dioxide + water

Observations:

1) Effervescence occurs. Colourless, odourless gas evolved which reacts with calcium hydroxide to form a white precipitate.

2) white solid dissolves to form colourless solution

For bases :

Acid + Bases --> Salt & water

Observations:

1) Heat is given out

2)White solid dissolves to form colourless solution

OKAY, I bet you guys also want to know what are some of the uses for acids besides knowing their chemical formulas.

USES of Acids :

1. Sulfuric acids :

(a) in making detergents

(b) in making fertilizers

(c)in car batteries

2. Ethanoic acid :

(a) (in vinegar) to prepare food

(b) in making adhesives such as glues

3. Hydrochloric acid :

(a) in leather processing

(b) in cleaning metals

Alright! I'm done here! Will be talking to you guys about bases is next week! Enjoy!:DD