Topics in ChemistryCompounds in Chemistry: Characteristics of Compounds Types of Mixture: Homogenous and Heterogeneous Mixtures Mixtures: Characteristics of Mixtures Physical Properties of Matter explained with Examples Chemical Properties of Matter explained with Examples Differences between Physical and Chemical Change Ionic Theory and Electrolysis Physical and Chemical Properties of Acids States of Matter: Characteristics of Solids Liquid State of Matter: Characteristics of Liquids Gaseous State of Matter: Characteristics of Gases Molar Mass, Worked Examples and Differences with Molecular Mass Elements: Characteristics of Elements Salts and Types of Salt in Chemistry Mixtures and Separation of Mixtures Mixtures and Separation of Mixtures - part 2 Mixtures and Separation of Mixtures - part 3 Physical Change and Chemical Change Concept of Ions and Electrolytes Grahams Law of diffusion, Worked Example and Importance
Academic Questions in Chemistry
Which of the following is NOT a characteristic of chemical change?
Which of the following statement is FALSE concerning a physical change _____.
The following substances will sublime EXCEPT _____.
Which of the following is a state of matter?
The ideal way of separating a mixture of blood is through _____.
Which of the following separation technique is used to separate an insoluble solid that sediments in a liquid?
A _____ mixture is said to be uniform all through.
The reaction involving an acid and a base is termed _____.
Mixtures will always require a form separation. The reason is because a mixture must contain more than one substance.
Take for instance, water (H2O) is a pure substance; but when we add common salt (NaCl) to it, the water no longer becomes pure (since it has been mixed with another substance).
Together, the water and salt are considered to be mixtures and thus may be separated in order to regain its constituents, that is, the salt and water respectively.
A mixture always contain two or more substances in any proportion.
Based on the uniformity of the mixture, we could classify a mixture as either homogenous or heterogeneous.
The liquid that dissolves the solid is known as the solvent. (Water in the above instance).
The solid that is dissolved by the solvent is known as the solute. (Salt in the above instance).
An example of a heterogeneous mixture is sand and water.
In chemistry, students are expected to work with substances like salts, acid and bases.
Recall that substances may be classified in two ways. These are:
Note: It is important to state that the technique for separating one mixture will vary with another. This is due to the different nature of components present in the mixture, together with their physical properties like boiling point, melting point and solubility among others.
Below are types of separation techniques (for separating mixtures):
Filtration is used as a method to separate an insoluble solid from a liquid. For instance, a mixture of:
Below is an image showing the Filtration process:
The material utilized in carrying out the process of filtration could be a filter paper, sieve with microscopic pores or even a cotton material.
The liquid that is collected into the filtration flask is known as the filtrate while the solid that remains on the filter paper is called the residue.
Note: Filtration is a commonly used process in the purification of a town’s water supply. In this case, filter beds are used.
Decantation is a process used for the separation of an insoluble solid from a liquid; and the insoluble solid must sediment (that is; settle at the bottom of the container), leaving a clear liquid above.
An instance where decantation can be used is in the separation of water and sand. Sand is insoluble in water and will sediment at the bottom, leaving a clear liquid above.
Sedimentation is a term used when an insoluble solid settle at the bottom of a container.
The clear liquid above the sediment is referred to as the supernatant.
During the process of decantation, we need to carefully pour off or decant the top/upper clear liquid (supernatant) leaving behind the insoluble solid (sediment) in the container.
Note: Although decantation may be quite similar to filtration with regards to what is separated, the fact remains that decantation is less effective since it cannot ensure complete separation of the insoluble solid from the liquid.
A separating funnel is used to separate two immiscible liquid, for instance, water and oil, kerosene and water, etc.
Note: The two immiscible liquids that are to be separated will usually have different densities or weights; and as a result, one will rise above the other.
With regards to water and oil, water has a higher density of 1.003g/m3 and will remain at the bottom (sinks) as the oil floats above it (since it has a lesser density of 0.811g/m3).
Immiscible or Non Miscible liquids are liquids that do not dissolve in each other.
Below is an image of a Separating Funnel:
When the mixture of the two immiscible liquid are put in the separating funnel, the tap/stopcock is opened and the liquid with the higher density is first collected (water in our case) followed by that with the lower density (oil).
A separating funnel is also called a separatory funnel.
Evaporation is used to separate the components of a soluble solid in a liquid and the solid must not be decomposed on heating.
A mixture of sodium chloride in water can be separated through evaporation.
The basic apparatus required to carry out evaporation are:
After evaporation, the liquid will be lost to the atmosphere while the solid (salt in our instance) remains in the evaporating dish.
The solid that remains in the evaporating dish is known as residue
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Amazing facts in Chemistry
The only letters that failed to appear on the periodic table are letters:
Gold and copper are the only two non-silvery colored metals. Please read some interesting facts about gold here
Copper is the only metal that is naturally antibacterial. This is why you would see some children carry copper water bottles to school
Water actually freezes faster when it’s warm than when it’s cold
Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy.
Please read on modification of Dalton's atomic theory here.
If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.
Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre
NOTABLE POINTS IN Chemistry