Classificação das soluções ​- Química - Ensino Médio

Summary

In this chemistry lesson, Professor Juliana Santiago introduces the classification of solutions, explaining the concepts of homogeneous mixtures, solvents, and solutes. She covers different types of solutions based on the physical state of the solvent—solid, liquid, and gas—and explores ionic and molecular solutions. The lesson also delves into solubility, defining the coefficient of solubility and explaining saturated, unsaturated, and supersaturated solutions. Through relatable examples like cooking and drinks, students learn how solutions behave, dissolve, and interact, with a focus on practical chemistry and everyday occurrences.

Takeaways

• 😀 Solutions are homogeneous mixtures of two or more substances, where the ions and molecules are evenly distributed.
• 😀 In everyday life, examples of homogeneous mixtures include hydrated ethanol (alcohol mixed with water) and homemade saline solution.
• 😀 A solution consists of a solvent, which is the substance in the larger amount, and a solute, the substance in the smaller amount.
• 😀 Solutions can be classified by the physical state of the solvent: solid, liquid, or gas.
• 😀 A solid solution, such as a metal alloy (e.g., bronze), consists of a solvent and solute in solid form.
• 😀 A liquid solution involves a solvent in liquid form, and the solute can be solid, liquid, or gas (e.g., salt dissolved in water or carbonated beverages).
• 😀 A gas solution consists of both solvent and solute in gas form, such as the air we breathe, which contains nitrogen, oxygen, and other gases.
• 😀 In a gas solution, nitrogen is the solvent since it is present in the largest quantity, not oxygen as commonly believed.
• 😀 Ionic solutions, like when salt (NaCl) dissolves in water, involve the dissociation of ions, which allows the solution to conduct electricity.
• 😀 Molecular solutions, such as when sugar dissolves in water, do not dissociate into ions and do not conduct electricity.
• 😀 Solubility refers to the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature, and it varies with temperature.
• 😀 A saturated solution occurs when the maximum solute is dissolved, while an unsaturated solution has less than the maximum. A supersaturated solution is unstable and can precipitate the solute out when disturbed.

Q & A

What is a homogeneous mixture, and can you give an example from the script?

A homogeneous mixture is a mixture where the components are evenly distributed, and you cannot distinguish one from another. An example from the script is the mixture of alcohol and water, where you cannot differentiate the two substances visually.

What is the difference between the solvent and solute in a solution?

The solvent is the substance present in the larger amount and is responsible for dissolving the solute. The solute is the substance present in the smaller amount and is dissolved by the solvent.

How does the physical state of the solvent affect the classification of a solution?

The state of the solvent determines whether the solution is classified as solid, liquid, or gas. For example, if both solute and solvent are in a solid state, the solution is classified as solid; if the solvent is liquid, the solution is classified as liquid; and if the solvent is gas, it is classified as gas.

Can you explain the example of bronze as a solid solution?

Bronze is an example of a solid solution, where the solvent is copper (present in the largest amount) and the solute is tin. It is not an element but a metallic alloy.

What is a liquid solution, and what are the states of the solute and solvent?

A liquid solution is formed when the solvent is in the liquid state, and the solute can be in a solid, liquid, or gas state. For example, when salt dissolves in water, the water is the solvent, and the salt is the solute.

What is an example of a gas solution, and how does it differ from a liquid solution?

An example of a gas solution is the air we breathe, which contains nitrogen as the solvent (present in the largest amount) and oxygen, argon, and other gases as solutes. Unlike liquid solutions, both the solute and solvent in a gas solution are in the gas phase.

What is the difference between ionic and molecular solutions?

In an ionic solution, the solute dissociates into ions when dissolved in the solvent, allowing the solution to conduct electricity. In a molecular solution, like when sugar dissolves in water, no dissociation occurs, and the solution does not conduct electricity.

What does solubility refer to, and how is it measured?

Solubility refers to the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature. It is measured in grams of solute per 100 grams of solvent, as shown in the script for sodium chloride (36 grams per 100 grams of water at 20°C).

What is a saturated solution, and how does it differ from unsaturated and supersaturated solutions?

A saturated solution contains the maximum amount of solute that can dissolve at a given temperature. An unsaturated solution has less solute than the saturation point, while a supersaturated solution contains more solute than it should, making it unstable.

How is the concept of solubility coefficient related to temperature?

The solubility coefficient indicates how much solute can dissolve in a specific amount of solvent at a given temperature. As the temperature changes, the solubility of a substance can increase or decrease.