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Do All Substances Dissolve? - Coggle Diagram
Do All Substances Dissolve?
Factors Affecting
Structure of the substance
The structure of a substance can greatly affect its solubility. A substance with high polarity will dissolve easier in something that also has a high polarity.
Temperature
The temperature of a substance can also affect its solubility.
A substance with a higher temperature increases the kinetic energy of its molecules allowing them to break down easier and thus dissolve.
Molecular Size
Molecular size is key for a substance to dissolve. A substance with large molecules is less soluble as this increases the difficult for the solvent to wrap around its molecules and dissolve them.
Variables
Independent Variables
Temperature of substance - temperatures of substances can affect solubility hence making this a valid independent variable.
Polarity of the substance - the polarity of the substance can affect its solubility as it determines the nature and strength of the intermolecular forces thus dictating the solubility of the solvent with the solute.
Dependent Variables
The dependent variable for this investigation would be the solubility of substance as this is what would change as the independent variable is manipulated
Controlled Variables
Solvent used
The solvent used is imperative to keep controlled as different Solvents have different structures and properties resulting in different levels of solubility. This could be kept controlled by only using 1 solvent such as water throughout the experiment
Temperature (If not Independent Variable)
Temperature can affect the substance's solubility by increasing its kinetic energy. This must be kept controlled as it would result in differing amounts of solubility if not controlled. To do so, a thermometer will be used to ensure the solute and solvent for each trial are kept at a consistent temperature.
Amount of Substance
The amount of substance must be controlled as using different amounts of the substance will result in lower or higher times of dissolving. To control this, a measuring cylinder will be used.
Uncontrolled Variables
Stirring Intensity and Speed
The speed and intensity at which the solvent and solute are stirred is an uncontrolled variable as it is unlikely to control this. To help control this variable an electric stirrer could be used at a consistent level.
pH of solvent and solute
The pH of the substance or the solvent could affect its solubility particularly if the substance is sensitive to ph changes. To minimise this you could perform a litmus test to ensure the pH of the solvent and solute is optimal.
Impurities
The presence of impurities in the substance is uncontrollable and could affect the substance's solubility. To reduce the impact of this variable one must ensure the substances being used are of high purity and could potentially conduct a preliminary purification process.
Background Information
What is a substance?
A substance is matter with a specific type of composition and properties. It cannot be physically separated into other components. Furthermore, substances can take 3 main forms, liquid, solid, and gas.
What types of substances are there?
There are two main types of substances, elements and compounds. Elements are substances that consist of only one type of atom whereas a compounds consists of two or more different types of atoms.
What is a solvent and a solute?
Together a solvent and solute make a solution. The solvent is the substance in which the solute is dissolved. It is usually greater in quantity compared to the solute. The solute is the substance that is dissolved in the solvent. It is usually lesser in quantity.
How do things dissolve?
The process of dissolution involves the breaking down of intermolecular forces holding the solute's particles together. The solvent and solute molecules collide together when mixed and this results in the breaking of the intermolecular bonds.
Limitations
The substance must be a liquid as to affect the solubility of a gas the manipulation of pressure is required, however, with the equipment present this is not possible.
The substance may also be limited by accessibility as well as safety. Certain substances may be hard to access or may be unsafe for a high school level experiment.
Furthermore, the equipment available is also limited. This could result in fewer experiments possible.