This lab is designed to allow you to practice making observations in the lab. There are certain terms that you must be familiar with in order to do that.
MISCIBLE OR IMMISCIBLE
In PART 1, we are mixing liquids and determining whether they are miscible or immiscible. If they are immiscible, you must determine which liquid is on top and which liquid is more dense.
Two liquids that are miscible are mixed and the resulting liquid appears the same throughout. There is no evidence of layers resulting from this mixing.
An example of two miscible liquids are water and rubbing alcohol.
Two liquids that are immiscible are mixed, with two distinct layers forming as a result.
An example of immiscible liquids are oil and water.
SOLUBLE OR INSOLUBLE
In PART TWO, you will be dissolving a solid in a liquid, and determining the solubility of the pure substance in that given liquid.
If the pure substance is soluble in the given liquid, the resulting solution is clear, but it may not necessarily be colorless. You will be able to see through that liquid with no solids present. Occasionally the solid partially dissolves in the given liquid. This means that pure substance is soluble in the liquid, but more liquid is necessary in order to completely dissolve the solid. A SOLUBLE SUBSTANCE WILL PARTIALLY OR COMPLETELY DISSOLVE IN THE GIVEN LIQUID.
The solid that is being dissolved is called the solute and will be the lesser amount while the liquid that the solid is dissolved in is called the solvent and will be in a greater amount.
A liquid can be soluble in another liquid. In that case, the solute is still the lesser amount and the solvent is the greater amount.
Examples of soluble substances
1) Salt dissolved in water
2) Instant coffee dissolved in water.
The solid substance will not dissolve at all in the liquid no matter how long you stir or shake the mixture. You may be able to see through the liquid but all of the solid you added will be present. The liquid will appear to be cloudy due to the suspended insoluble solid.
An example of an insoluble substance is sand mixed into water.
PHYSICAL OR CHEMICAL CHANGE
In PART THREE, you are to determine if a chemical reaction occurs when you combine two solutions. If a chemical reaction occurs you must be able to state your evidence for your decision.
Two substances are combined and the result is that you have simply altered the appearance of the substances. You have not created a new product. If you get a color change that is lighter than the original substances without any other changes, you have altered the appearance through dilution.
An example is Big Red with water added, result is lighter red due to dilution.
CHEMICAL CHANGE or REACTION
Two substances are combined resulting in a new product or products. A chemical change is accompanied by any, all of, or a combination of the following: precipitation, effervescence, and color change.
EVIDENCE OF CHEMICAL CHANGE OR REACTION
A precipitate is an insoluble solid product that is formed due to the reaction. The solid may be distributed throughout the solution giving the solution a CLOUDY appearance. If the precipitate is throughout the solution you will not be able to see through the liquid, until the solid has been given the time to settle to the bottom. A precipitate can also fall immediately to the bottom of the container upon mixing the solutions.
A precipitate is present if the solution has a solid at the bottom of the container or if the solution is cloudy.
An example would be a yellow solution of potassium chromate mixed with a colorless solution of barium nitrate. The resulting solution is yellowish brown and cloudy. The yellowish brown precipitate will settle out over time.
Effervescence is the formation of gases which produces bubbles.
Examples of Effervescence:
Alka selser in water
A clear, colorless solution of sodium bicarbonate mixed with clear, colorless vinegar with bubbling resulting.
3) COLOR CHANGE
Any of the following are considered a color change indicating a chemical reaction.
a) A color that was not originally present in either of the reactants.
b) A color that is darker that one of the reactants.
c) A color that is lighter than one of the reactants and is accompanied by precipitation and/or effervescence.
Examples of Color Change:
A colorless liquid added to a colorless liquid resulting in a bright yellow liquid.
A light blue liquid is added to a colorless liquid resulting in a deep blue liquid.
A deep read liquid is added to a colorless liquid resulting in a light red liquid and effervescence.
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