1.4 - 1.7 Solubility
1.4 Activity 5 : Defining diffusion, diluting and dissolving
Gases can diffuse into each other . This is because the particles in a gas are in a state of constant random motion.
Liquids can diffuse into other liquids. When the two liquids mix well in each other they are said to be soluble.The diffusing of one liquid ( the solute) into another ( the solvent) results in the dilution of the solute by the solvent.
The food colouring video here shows dilution in action.
Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.
Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to a solution.
Solids, liquids, and gases can all dissolve. Dissolving depends on the molecules of the substance doing the dissolving, called the solvent, and the molecules of the substance being dissolved, called the solute. Dissolving is the process in which these molecules interact and attract each other to form a solution.
Watch both the video and the animation carefully.
In your own words:
- Describe what happens.
- Try to explain what happens
- Explain why the colour spreads faster in the hot beaker
Use the each of the following words at least once:
food colouring, dissolve, particles , constant motion, soluble, water , faster , diffuse , diluted
1.4 - 1.7 What's the best solution?
Students should:
1.4 know what is meant by the terms: solvent, solute, solution, solution, saturated solution.
1.5C know what is meant by the term solubility in the units g per 100 g of solvent
1.6C understand how to plot and interpret solubility curves
1.7C practical: investigate the solubility of a solid in water at a specific temperature
Watch the video carefully and write down your answers to the questions before revealing them by clicking on each questions in turn.
The solublity of a substance is a physical property.
Other physical properties are :
- melting point
- boiling point
- density
- conductivity
The solublity of most solids increases as the temperature increases. This rule applies to most solids but is the opposite with gases. Gases become less soluble as the temperature increases.
The solubility of a substance is often measured in grams per 100g water. These are the units used in the video shown.
The solubility of copper sulfate is greater than that of potassium sulfate at all temperatures.
The solubility of potassium sulfate at 60oC is 18g/100cm3
What is a saturated solution ?
When a saturated solution is cooled - it becomes a super saturated solution and crystallisation takes place.
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