Types of Matter: Chemical and Physical Changes
el 1: Examples of various types of matter at room temperature
Formula
State (or states)
Classification
Item
Al(s)
Solid
Element
Aluminum
H,(g)
Gas
Element
Hydrogen
(1)
H2O
Liquid
Compound
Water
NaCl(s) .
Solid
Compound
Table salt
H2O(o and NaCI(aq)
Aqueous solution
Homogeneous mixture
Salt water
H2O(t and many others
Aqueous solution
Homogenous mixture
Coffee black
H,O0 and other stuff
Liquid + solid
Heterogeneous mixture
Muddy water
Questions
1. Consider Model 1. How does the formula of an element differ from that of a compound?
2
Hypothesize on the meaning of the labels (s), (9), (g), and (aq) on the formulas.
Information: States of Matter
Matter can be classified by its physical state (or phase): solid, liquid, or gas. Most substances can
exist in each of the three states depending on temperature and pressure. For example, H2O is nounally
a liquid at room temperature, ice at temperatures below 0°C, and vapor at temperatures above 100°C.
Although we think of iron as a solid, it can be melted and even vaporized if the temperature is high
enough. Changes between these states are usually considered physical-not chemical- changes, since
the chemical formula is the same.
The phase labels (s), q), or (g) can be written after a formula to signify the physical state. So, H2O(g)
would mean gaseous water or water vapor.
5. Describe what is happening in this process: H200--* H2O(s)
6. Would the process in question 5 be considered a chemical or physical process? Explain.
Information: Classifications of matter
Chemistry is the science that deals with matter and the changes matter undergoes. Matter can be
divided into two main types: pure substances and mixtures of substances.
A substance cannot be separated into other kinds of matter by physical processes such as filtering of
evaporation, and is either an element or a compound. Compounds are made of two or more elements
chemically combined. The elements themselves cannot be separated into simpler substances even by
a chemical reaction.
On the other hand, mixtures can be separated by physical means. Mixtures that have the same
composition throughout are called homogeneous (salt water); those that do not are called
heterogeneous (Italian salad dressing).
Atoms of a single element can exist as individual atoms (aluminum) or in chemical combination for
form molecules (hydrogen). When atoms of two or more elements combine chemically they form
compounds (water). Subscripts following an element in the foiniula represent the number of atoms
of that element in the formula.
Model 2 : Flow chart for classifying matter
Matter
Pure Substance~—
Element
Compound
Mixture
Heterogeneous
Homogeneous
Exercises:
1. Using a periodic table, identify the elements represented in each formula, and state the number of
atoms of each element in the formula. The first one has been done for your.
a. NH3 (ammonia)
one nitrogen atom, three hydrogen atoms
b. C6H12O6 (glucose)
c. Mg(OH)2 (milk of magnesia),
d. H2SO4 (sulfuric acid)
e. C2HSOH (ethanol)
2. Find the names of the following elements.
a. Na ((#11)
b. K(# 19)
c. Ag (#47)
d. W(#74)
e. Au (#79)
f. Hg (#80)
g. Sn (#50)
h. Pb (#82)
i. Fe (#26)
j. Cu (#29)
k. Sb (##51)
3. Using the flow chart in Model 2 to help you, classify each of the following as either a mixture or
pure substance. For each substance, tell whether it is an element or a compound. For each mixture,
tell whether. it is homogeneous or heterogeneous.
b. air
a. a lead (Pb) fishing weight
c. apple juice
d. concrete
e. baking soda (NaHCO3)
f. beach sand
g. 14-karat gold ring
h. whole blood
i. 24-karat plated gold coin
j. helium in a balloon
k. dry ice (solid carbon dioxide)