The solutions unit investigates when various compounds are dissolved into solution and its properties when in solutions.
Here are the vocabulary needed for the first section
- Pure substances
- Homogenous mixture
- Heterogeneous mixture
Do you recall what matter is?
As a recap, matter is anything that takes up space. Therefore anything that occupies would be considered as matter. Things such as your pen, the table, clouds, water, and the gas in a balloon can all be considered as matter since they take up a region of space. Even things that you cannot see such as gases would still be considered as matter.
But is all matter a solution that they are mixed in with something else or can there be pure substances?
Matter can be broken down into two main large subsections, pure substances, and mixtures.
Pure substances are basically matter than has not been mixed with any other substance. They are found in how they would be found naturally. All the properties in a pure substance would be the same as a whole. Examples are Oxygen, Nitrogen, (basically ALL elements on the periodic table), water, sugar and etc…
From the examples above, do you notice any striking categories?
Yes, you might be able to separate the above examples into two sub-categories, elements and compounds.
Elements – as in the elements found on the periodic table are pure substances. They are the ultimate pure substances since nothing can be more pure than the elements found on the periodic table. Nothing mixed together can form the elements of the Periodic table unless you bombard extra protons to form the new elements (which essentially is the theory behind the Big Bang). As an analogy, elements are like Lego pieces while compounds are the structures formed by many different Lego pieces.
The second sub-category is compounds:
Compounds are not elements since they require more than 1 element to form. Examples such as water, salt, sugar, DNA, and many others are considered as compounds because as a compound, they do not require any other substance to help them function. However, their properties are the same throughout the entire compound. For example, water is made up of 2 Hydrogen atoms and 1 Oxygen atom, when the elements are combined to each other; the H2O is now an entirely new substance by itself. The properties of water are for the entire water molecule, not the individual elements of hydrogen and oxygen. The water molecule does not need any other element to help it become “water”. Thus, it is a compound.
In this unit, since it is called Solutions, mixtures are the focus.
Mixtures can be broken down into two types of mixtures, homogenous and heterogeneous
What makes a mixture a mixture is that in a mixture, more than one “particle” exists. Salt water would be an example since the mixture would have salt plus water. If we were to take salt water and have it evaporated, it would separate the mixture into salt and water. A formal definition of a mixture is that the individual “particles” such as the water and salt would retain their own individual properties.
The two types of mixtures, heterogeneous and homogeneous can be confusing at times since some solutions can be quite ambiguous. The important aspect is to analyze if the mixture is either evenly distributed or unevenly distributed. If we look at salt, the mixture would be a heterogeneous mixture if the salt is mixed in with paper, something that can be easily picked out, compared to salt in water, in which the salt cannot easily picked out.
In heterogeneous mixtures, the substances can be easily distinguishable but again, they can be confusing at times.
Look at mayonnaise for an example, Mayonnaise looks like a homogeneous mixture since it appears to be evenly distributed, but if you let mayonnaise settle, the oil will be separated from the stirred egg yolk. Thus, mayonnaise would be classified as a heterogeneous mixture. To further classified heterogeneous mixture, mayonnaise would be an example of an emulsion mixture.
Emulsion mixture is when there are two liquids in the solution. Mayonnaise has egg yolk and oil, thus an emulsion. Another example of emulsion mixture is salad dressing (when stirred). The salad dressing will settle and separate into layers.
Another type of heterogeneous mixture is called a suspension. A suspension is when solids are mixed in with another liquid. The solid will be easily separated from the liquid making it still a heterogeneous mixture. Example: sand water, vegetables in soup etc…
In Homogeneous mixture, they are known as solutions. Recall, homogeneous solutions are evenly distributed in the solution. If a homogeneous solution is left out, it will not settle out into different layers. Furthermore, the solution cannot be easily filtered out.
Features of homogeneous mixtures:
What exactly is a solution?
- A solution contains two or more substances that are evenly distributed (homogeneous mixture)
- Solute and a solvent
- Solute – dissolved particles in a solution.
- Ex: sugar
- Solvent – dissolving medium in a solution
- Ex: Water
- Solute – dissolved particles in a solution.
If both dissolving substances are liquids, the dominant substance in the mixture will always be classified as the solvent.
Types of Solutions
|Liquid||Solid||Sugar in water|
|Liquid||Liquid||Alcohol in water|
|Liquid||Gas||CO2 in water|
|Solid||Solid||Brass (Cu and Zn)|
|Solid||Liquid||Dental amalgam (Hg in Sn)|
|Solid||Gas||Gas in carbon filters|
|Gas||Solid||Microparticles in air|
|Gas||Liquid||Gas in air|
- Describe and give examples of various types of solutions. Include: all nine possible types
- Describe the structure of water in terms of electronegativity and the polarity of its chemical bonds.
- Explain the solution process of simple ionic and covalent compounds, using visual, particulate representations and chemical equations. Include: crystal structure, dissociation, hydration
- Interpreting a a solubility curve of a pure substance in water and differentiate among saturated, unsaturated, and supersaturated solutions.
- Explain how a change in pressure affects the solubility of gases.
- Explain freezing-point depression and boiling-point elevation at the molecular level. Examples: antifreeze, road salt…
- Include: grams per litre (g/L), % weight-weight (% w/w), % weight-volume (% w/v), % volume/volume (% v/v), parts per million (ppm), parts per billion (ppb), moles per litre (mol/L) (molarity)
- Prepare a solution, given the amount of solute (in grams) and the volume of solution (in millilitres), and determine the concentration in moles/litre. (Molarity)
- Solve problems involving the dilution of solutions.
Include: dilution of stock solutions, mixing common solutions with different volumes and concentrations