Ácidos - Brasil Escola

Summary

In this introductory chemistry lesson, the professor explains acids, starting with their etymology from the Latin word 'acidus,' meaning sour. The video delves into three key acid definitions: Arrhenius (acids release H+ in water), Brønsted-Lowry (acids donate protons), and Lewis (acids accept electron pairs). Examples from daily life, such as acetic acid in vinegar, citric acid in citrus fruits, and phosphoric acid in sodas, are used to demonstrate the prevalence of acids. The professor also shares amusing anecdotes and encourages viewers to engage with the content on social media and podcasts.

Takeaways

• 😀 The word 'acid' comes from the Latin 'acidus', meaning sour or sharp, but not all acids are sour.
• 😀 The script introduces three main theories for defining acids: Arrhenius, Bronsted-Lowry, and Lewis.
• 😀 According to Arrhenius, an acid is a compound that releases H+ ions in aqueous solution.
• 😀 Bronsted-Lowry's definition states that acids are substances that donate a proton (H+), without the need for water.
• 😀 Lewis defines acids as substances that can accept a pair of electrons in a chemical reaction.
• 😀 Common acids in daily life include acetic acid (found in vinegar), phosphoric acid (used in soft drinks), and citric acid (found in citrus fruits).
• 😀 Carbonic acid is present in carbonated beverages, and it is one of the reasons why sodas are fizzy.
• 😀 Acids like acetylsalicylic acid (aspirin) and lactic acid (found in milk) are commonly encountered in everyday life.
• 😀 The formic acid from ant bites is mentioned, explaining the sharp pain caused by the sting due to its acidic nature.
• 😀 The script emphasizes the wide presence of acids in various foods, beverages, and even in natural occurrences like insect stings.

Q & A

What is the origin of the word 'acid'?

The word 'acid' comes from the Latin word 'acidus', meaning sour or tart, though not all acids have a sour taste.

What are the three common theories for defining acids?

The three common theories for defining acids are: 1) Arrhenius theory, which defines acids as substances that release H+ ions in water; 2) Brønsted-Lowry theory, which defines acids as molecules or ions that donate a proton (H+); and 3) Lewis theory, which defines acids as substances that accept a pair of electrons.

How does the Arrhenius theory define an acid?

The Arrhenius theory defines an acid as any compound that, when dissolved in water, releases H+ ions.

What is the Brønsted-Lowry theory's definition of an acid?

According to the Brønsted-Lowry theory, an acid is a molecule or ion capable of donating a proton (H+), regardless of whether it is in water.

What does the Lewis theory of acids entail?

The Lewis theory defines an acid as any molecule or ion that accepts a pair of electrons during a reaction.

Why is it not ideal to associate acids with sourness alone?

It is not ideal because not all acids taste sour. For instance, sulfuric acid or hydrochloric acid are acids, but they do not have a sour taste, and they are not safe to taste.

Can you give an example of an acid in everyday life?

An example of an acid in everyday life is vinegar, which contains acetic acid. Other examples include citric acid in citrus fruits and phosphoric acid in soft drinks.

What role does acetic acid play in vinegar?

Acetic acid is the active component in vinegar, typically making up 4 to 7% of the composition, contributing to its acidic and tangy taste.

How does carbonic acid form in beverages?

Carbonic acid forms in beverages like soda and sparkling water when carbon dioxide (CO2) dissolves in water, creating an effervescent reaction.

Why does the bite of a fire ant hurt?

The pain from a fire ant bite is caused by the injection of formic acid into the skin. This causes a burning or stinging sensation.