Lesson 5 - Classifying Chemicals Using Properties

Lesson 5 - Classifying Chemicals Using Properties

Vocabulary

matter, mechanical mixture, mixture, properties, pure substance, solution

Matter can be classified as either a mixture or a pure substance. Mixtures contain at least two substances. If you can see the different parts of the mixture it is called a mechanical mixture.

Ex. Soil, granola cereal, concrete

If the substance appears to be one substance, it is called a solution.

Ex. Vinegar, pop, coffee

Properties of mixtures depend on the proportions of the parts. Have you ever made lemonade using too much powder? That'll make ya pucker!

Ex. Sweetness of pop, hardness of cement

Pure substances have properties that are always the same. You can identify an unknown substance by testing its properties.

Ex. Salt, carbon, gold

Click on the item that is not a mechanical mixture?

Which item is a solution?

What made it possible for you to determine whether or not it was a mechanical mixture? What about the other substances? Is it hard to tell them apart?

Of course. It is hard to determine whether they are solutions or pure substances by just looking at them. You must take into consideration all of their physical properties. Remember...Properties are characteristics that you can use to describe or identify different substances!

Can you name three properties that would be useful or helpful in determining whether they are solutions or pure substances?

We can check whether the melting point, boiling point or density on the labels match the information in the table below. If they do match, we can say the the substances are more than likely a pure substance.

In the following lab you will examine samples of unknown substances. While you examine these substances you need to try and classify them as either a mechanical mixture, a solution or a pure substance.

Make sure you read and then write out the lab before you begin. Remember to follow the safety precautions of working in the lab and have all of your materials prepared before you start!

LAB 5: CLASSIFYING CHEMICALS WITH DATA (Write out the lab).

PROBLEM: How can you classify unknown materials as mechanical mixtures, solutions or pure substances?

HYPOTHESIS: How do you think it is going to turn out? Use the facts you already know to come up with a guess that might really make sense.

MATERIALS:
-12 samples of unknown materials
-data table about properties of pure substances (See below).

TABLE: PROPERTIES OF SOME PURE SUBSTANCES

PURE SUBSTANCE	MELTING POINT (0C)	BOILING POINT (0C)	DENSITY (g/cm3)	APPEARANCE
ethanol (alcohol)	-115	78	0.8	clear colourless liquid
aluminum	660	Substance decomposes(break apart) rather than change state.	2.7	silvery-coloured solid
sodium bicarbonate (baking soda)	Substance decomposes(break apart) rather than change state.	Substance decomposes(break apart) rather than change state.	2.2	white solid
copper (II) sulphate (bluestone)	Substance decomposes(break apart) rather than change state.	Substance decomposes(break apart) rather than change state.	2.3	blue solid crystals
carbon (diamond)	3500	3930	3.5	colourless solid crystals
carbon (graphite)	4000	3930	2.3	grey-black solid
copper	1084	2336	9.0	shiny reddish solid
glycerol (glycerine)	18	Substance decomposes(break apart) rather than change state.	1.2	colourless thick liquid
iron	1535	3000	7.9	grey solid
lead	327	1750	1.3	blue-grey solid
calcium carbonate (limestone)	Substance decomposes(break apart) rather than change state.	Substance decomposes(break apart) rather than change state.	2.9	grey-white solid
naphthalene	80	216	1.2	white solid
sodium chloride (table salt)	801	1465	2.2	white solid
calcium hydroxide (slaked lime)	Substance decomposes(break apart) rather than change state.	Substance decomposes(break apart) rather than change state.	2.2	white solid
sucrose (sugar)	170	Substance decomposes(break apart) rather than change state.	1.6	white solid
sulphur	113	445	2.1	yellow solid
tin	232	2270	7.3	silvery-yellowish solid
water	0	100	1.0	clear colourless liquid

Download Properties of Pure Substances

PROCEDURE:
1. Write out the lab and make sure you have two observation tables. (a rough copy and a good copy to submit with your lab). Observation table

2. Examine each sample and describe its properties. Make sure to note information on the labels.
**Remember. . . DO NOT OPEN THE VIALS!**

ANALYSIS:
1. Compare the properties of the unknown materials to the pure substances on the data table. Classify each unknown substance as a mechanical mixture, a solution or a pure substance.

2.
a) If an unknown sample is a pure substance, identify the pure substance.
b) If an unknown sample is a mechanical mixture or a solution, identify what pure substances it might contain.

CONCLUSION: You must say what you found out during the lab. You figure out whether your results agreed with your hypothesis or not. Put everything you observed together and try to make some sense out of it.
**Hint** The conclusion should answer the problem.

Lab Report Evaluation