Chapter 17

 

Objectives: Differentiate between element and compound.

Differentiate between homogeneous and heterogeneous mixtures.

Compare and Contrast solution, colloid, and suspension.

 

Matter is made up of small particles called atoms.

A substance is an element or a compound that can not be broken down any farther and still maintain its properties. 

An element is a substance with atoms that are alike.

The list of elements can be found on the periodic table.

A compound is two or more elements combined.

A compound has atoms that are different.

Water and salt are two examples of compounds.

A mixture is a combination of substances that can be separated by physical means.

Homo – same               Hetero – different

Homogeneous mixture is evenly mixed and looks the same throughout.

Heterogeneous mixture is unevenly mixed and has distinctly different layers.

Another name for a homogeneous mixture is a solution.

Two special cases of a heterogeneous mixture are colloids and suspensions.

A colloid has particles that do not settle but scatter light.

A suspension has particles that settle and scatter light.

                        Concept Map of Matter

 

                                                            Matter

                                                                                                                                                                                                                                    Substance                                                                     Mixture

 

Element                        Compound                   Homogeneous              Heterogeneous

 

                                                                        Solution            Colloid             Suspension

 

 

 

Ex. Gold, silver salt, water                     kool-aid           milk                  orange juice

 

Examples of a colloid is fog, smoke, and milk.

Examples of suspensions are medicines that must be shaken up and orange juice.

 

 

 

 

 

 

 

Objective:  Identify and distinguish physical properties, physical changes, chemical properties, and chemical changes.

 

Physical properties are any characteristics of a material that does not change the identity.

Examples are color, shape, size, density, melting point, and boiling point.

Physical properties describe appearance, behavior and are used to separate materials.

Physical changes are a change in size, shape, or state.

Physical changes do not change the identity.

Chemical properties are characteristics that indicate that a substance can undergo a chemical change.

Examples are flammability and exposure to light.

Chemical changes are when a substance is changed into a new substance.

Examples are burning and rusting.

 

Objective – Discuss the conservation of mass in chemical changes.

The Law of Conservation of Mass states that mass can not be created nor destroyed.

The mass before a chemical change will equal the mass after a chemical change.

 

Ex.      Na   +    Cl   →   NaCl

 

If 36 grams of  Na is combined with 22 grams of Cl, how much NaCl is produced?

 

Na + Cl   =  NaCl

36 + 22   = x

58  = x

58 grams of NaCl is produced.

 

CH4      +     2 O2                    →              CO2               +          2 H2O

 

In the above reaction, 45 grams of CH4 are combined with 122 g of O2 to produce 87 grams of CO2.  How much water is produced?

 

CH4      +     2 O2                    →              CO2               +          2 H2O

45       +       122                     =             87                  +         x

167 = 87 + x

80 = x

80 grams of H2O