1. Chapter 1: Matter & Measurement
Chemistry Lecture 3
Chapter 1: Matter & Measurement
Chapter Highlights
physical properties & states of matter
basic kinetic molecular theory
identify elements by name and symbol
atom, element, molecule & compound
physical versus chemical changes
homogeneous & heterogeneous mixtures
metric system
precision & accuracy and significant figures

2. Chemistry Lecture 3
Three States of Matter
In a chemical context, matter, can exist in one of three distinct forms, phases or states of matter.
Solids are rigid, have fixed volume and are noncompressible.
Liquids change shape but have a reasonably fixed volume and are essentially noncompressible.
Gases (vapours) readily change shape and volume & are highly compressible.

3. Physical & Chemical Properties
Chemistry Lecture 3
Physical & Chemical Properties
Properties of substances can be divided into physical and chemical.
Physical properties are those that describe a substance as it is. For example; colour, density, hardness, melting point etc.
Chemical properties are those that describe how a substance can be transformed. For example; flammability, solubility, corrosiveness, etc.

4. Basics of the Kinetic Molecular Theory
Chemistry Lecture 3
Basics of the Kinetic Molecular Theory
Used to interpret the behaviour of solids, liquids & gases
Definition: all matter consists of extremely small particles which are in constant motion.
the higher the temperature the faster the particles move
the kinetic energy of motion competes with the forces of attraction between particles
this allows for melting of a solid or vapourization of a liquid as the temperature increases

5. Substances have fixed compositions and distinct properties
Chemistry Lecture 3
Substances
Substances have fixed compositions and distinct properties
Pure substances are substances that are free from impurities.
Impurities are trace quantities of substances in a sample other than the principal component.
Most naturally occurring samples of matter consist of two or more substances.

6. Mixtures are combinations of more than one substance
Chemistry Lecture 3
Mixtures
Mixtures are combinations of more than one substance
Homogeneous mixtures: all species are in the same phase and uniformly distributed throughout the sample.
Heterogeneous mixtures: all species are not in the same phase or they are not uniformly distributed
Separated by
physical methods
MIXTURES
MATTER
gas, liquid, solid
PURE
SUBSTANCES
homogeneous
chemical methods
elements
compounds

7. Chemistry Lecture 3
Elements
Elements are substances that cannot be decomposed into simpler substances by chemical means.
Only a few of the elements are abundant on Earth.
Two elements comprise the majority of the Earth's crust
The human body concentrates three elements

8. Chemistry Lecture 3
Compounds
Compounds consist of more than one element united chemically in definite mass proportions.
The law of constant composition or law of definite proportions states that, for a given chemical compound, the mass proportions of the elements are always the same.
butane has chemical formula: C4H10

9. For example, there are 100 centimeters in a meter.
Chemistry Lecture 3
Measurement
The metric system of units is attractive since all related units differ by powers of ten:
For example, there are 100 centimeters in a meter.
SI (Système International d'Unités) is the recognized set of fundamental metric units for scientific measurement.
mass Kilogram (kg)
length Metre (m)
time Second (s)
electrical current Ampere (A)
temperature Kelvin (K)
light intensity Candela (cd)
amount of substance Mole (mol)

10. Metric uses prefixes to indicate subunits.
Chemistry Lecture 3
Metric System
Metric uses prefixes to indicate subunits.
For example;
1 centimeter (cm) = 1/100 meter = 1 x 10-2 m
1 millimeter (mm) = 1/1,000 meter = 1 x 10-3 m
1 nanometer (nm) = 1/1,000,000,000 meter = 1 x 10-9 m
Others quantities are derived from these.
Volume of a box is given by the product of the lengths.
One Liter is the volume of a box that is 10 centimeters on each side; 1 L = 1000 cm3 or 1 mL = 1 cm3.
Density is the ratio of mass to volume of a sample (g/mL). For a pure substance, density is constant.

11. Precision & Accuracy Precision is a measure of random error;
Chemistry Lecture 3
Precision & Accuracy
Precision is a measure of random error;
(the less the random error, the higher the precision)
Precision refers to the reproducibility of a measurement.
Accuracy is a measure of systematic error;
(the less the systematic error, the higher the accuracy)
Accuracy refers to the agreement of a measurement with the "correct" value.

12. Precision & Accuracy in Numbers
Chemistry Lecture 3
Precision & Accuracy in Numbers
Exact numbers are those that are infinitely precise.
Most exact numbers are integers, such as….
12 eggs = 1 dozen, and are not measurements
(1 mole = x 1023).
Inexact numbers result from measurements
and are subject to error.
Precision and accuracy represent the two types of error.

13. Significant figures reflect precision.
Chemistry Lecture 3
Significant Figures
Significant figures reflect precision.
All of the known digits are reported plus a last, estimated, digit.
For example:
a measurement with a metric ruler, graduated in mm, might be reported as "27.6 mm" showing what the scale actually has markings for (27 mm) and an estimate “between-the-lines" (.6 mm).

14. Application of Significant Figures
Chemistry Lecture 3
Application of Significant Figures
Question:
What is the difference between 4.0 g and 4.00 g?
Answer:
4.0 has two significant figures: 4.0 ± 0.1
4.00 has three significant figures: 4.00 ± 0.01
A balance has precision of ± g. How many significant figures should be reported for a sample that weighs about 25 g?
Five!!!