KS3 Science, Chemistry; Lesson 2: Dissolving

Summary

In this video, we explore the science of dissolving, breaking down key concepts like solvents, solutes, solutions, and saturation. Using simple demonstrations, the video explains how solids (like salt) dissolve in liquids (like water) at the particle level. Key terms are introduced, such as 'soluble' (can dissolve) and 'insoluble' (cannot dissolve). The video also covers factors that affect the dissolving process, including stirring, temperature, and the amount of solvent. Finally, it explains the concept of saturation, where the solvent can no longer dissolve more solute. This engaging and informative video offers both theoretical insights and practical demonstrations.

Takeaways

• 😀 Dissolving occurs when a solid or gas is mixed into a liquid, making the solid appear to disappear, although it is still present in the solution.
• 😀 A **solvent** is the liquid that dissolves a substance, while a **solute** is the substance being dissolved.
• 😀 The combination of a solute and solvent forms a **solution**.
• 😀 The terms **soluble** and **insoluble** describe whether a substance can dissolve in a liquid, with soluble substances able to dissolve and insoluble ones unable to do so.
• 😀 Stirring increases the rate of dissolving by helping particles of the solute find the gaps between the solvent molecules.
• 😀 Increasing the amount of solvent provides more space for the solute to dissolve, speeding up the process.
• 😀 Raising the temperature makes the solvent particles move faster, which allows the solute to dissolve more quickly.
• 😀 The **saturation point** is the maximum amount of solute that can dissolve in a solvent at a given temperature.
• 😀 At 25°C, water can dissolve up to 35.7 grams of salt per 100 milliliters, and the saturation point increases with temperature.
• 😀 A substance that cannot dissolve in a solvent is **insoluble**, like chalk or flour in water.
• 😀 Different liquids, like water, alcohol, or acetone, can be used as solvents, depending on the solute being dissolved.

Q & A

What is dissolving?

Dissolving is the process where a solid or gas is mixed into a liquid, and after some time, it appears to disappear, even though it hasn't. The solute particles fit into the gaps between the solvent particles.

What are the terms used for the components involved in dissolving?

The liquid that dissolves the solid is called the solvent, and the solid being dissolved is called the solute. The mixture formed by the solvent and solute is called a solution.

What is an example of a solute and solvent?

An example of a solute is table salt (sodium chloride), and an example of a solvent is water.

What happens when salt is dissolved in water?

When salt dissolves in water, the salt particles fit into the spaces between the water molecules. This makes the salt seem to disappear, but it is still present in the solution, which can be tasted (salty water).

How can the rate of dissolving be increased?

The rate of dissolving can be increased by stirring the mixture, adding more solvent, or raising the temperature. Stirring helps the particles move around faster, and higher temperatures make the particles move more quickly, allowing them to fit into the gaps more easily.

What is solubility?

Solubility refers to the ability of a substance (solute) to dissolve in a solvent. If a substance can dissolve, it is called soluble. If it cannot, it is insoluble.

What does the term 'insoluble' mean?

Insoluble means that a substance cannot dissolve in a given solvent. For example, chalk or flour is insoluble in water.

What is the saturation point?

The saturation point is the maximum amount of solute that can dissolve in a solvent at a given temperature. Beyond this point, no more solute can dissolve, and any extra solute will remain undissolved at the bottom.

How does temperature affect the saturation point of a solution?

Increasing the temperature allows the solvent's particles to move faster, which increases the saturation point. For example, at 25°C, 35.7 grams of salt can dissolve in 100 milliliters of water, but at 40°C, the saturation point increases to 40 grams of salt.

What is an example of a solute that dissolves well and one that doesn't?

Sugar and salt are examples of solutes that dissolve well in water (they are soluble), while substances like chalk or flour are insoluble and do not dissolve in water.