Why study chemistry?
1. It’s required.
2. It sounds interesting.
3. It’s unavoidable.
4. It truly is the central science.
Introduction: Matter and Measurement
Chapter 1 BLB 11th
Expectations
Classify matter Properties of matter g ↔ mL (using density) Solve for any variable in a formula. Metric unit conversions Other conversions: temperature, metric-
English, etc. Identify and work with significant figures.
1.1 The Study of Chemistry
Chemistry is everywhere! Matter is everywhere! Thus, chemistry matters!
Chemistry involves the study of matter – its properties and behavior.
Macroscopic observations are rooted in microscopic structure.
The Periodic Table of the Elements
Checking in…
Name an element:
Name a compound:
Name a mixture:
A. There are three atoms making up a water molecule.
B. The water molecule contains atoms of two different types of elements.
C. A water molecule has more than one bond.
D. A water molecule has a larger mass than the sum of masses of its constituent atoms.
Molecules
O2, H2O, CO2, C2H5OH, C2H6O2, C9H8O4
Models shown on p. 4
1.2 Classification of Matter
Matter – anything which has mass and takes up space.
States of matter (p. 7):1. Solid – rigid, regular
2. Liquid – fluid, irregular
3. Gas – open, random
Phases of matter
States of Matter
States of Matter
Physical or chemical separation?
The Periodic Table of the Elements
Elements
Group Activity
Assemble into groups of four or five.
Introduce yourself.
Work together.
Discuss, argue, and intellectually engage.
Record and report your group’s result.
Group Activity
Describe the contents of the containers.
Devise a plan to determine which liquid is in each of the two containers.
Description
Strategy for identification
1.3 Properties of Matter
physical – measured or observed without changing the identity of a substance, e.g. physical state, color, odor, density, boiling point
chemical – describes a substance’s reactivity, e.g. flammability, corrosiveness
extensive – depends on the amount of matter present, e.g. mass, volume
intensive – does not depend on the amount of matter present, e.g. density, color, temperature
Physical & Chemical Changes
Physical – change in appearance, not in composition, e.g. phase changes, separation of mixtures: filtration, distillation, chromatography
Chemical – new substance is formed as the chemical identities change, e.g. any chemical
Dissolve vs. react Explode vs. ignite
Physical or chemical?
Helium leaks out of a balloon? Growth of plants by photosynthesis? Salt added to a bowl of soup? Blood turning red upon exposure to air?
Mixture, compound, pure substance?
Fruit punch? Sugar? Milk? Gold? Tap water?
1.4 Units of Measurement (SI Units)
Volume – a derived unit
Angstrom Å 10-10 m
Temperature Scales
Temperature Conversions
°F → °C
°C → °F
°C → K
)32(9
5 FC
32)(5
9 CF
15.273 CK
Density
Density – mass per unit volume
D = m/V (g/cm3 or g/mL) Measured at a specific temperature Useful as a conversion factor (g ↔ mL) Most substances become more dense at lower
temperatures. Specific gravity – density of a substance
divided by the density of a reference substance (usually water); no units
Difference in density values is the reason some things float and others sink.
0.91
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
0 10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
Temp. (oF)
Den
sit
y (
g/m
L)
Ice, 0.917
Water, 0.99987
Density of Water
Calculate the volume (in mL) of 87.6 g of platinum. (DPt = 21.5 g/cm3)
1.5 Uncertainty in Measurement
Exact numbers have a defined value, e.g. 12-dozen, 2.54 cm/in; 1000 g = 1 kg; count of objects
All measurements have some degree of uncertainty; inexact
Types of error: systematic & random The last digit of a measured quantity is uncertain. The more significant figures, the greater the certainty. precision – agreement among data accuracy – agreement of data with true value
Different measuring devices have different uses and different degrees of accuracy and precision.
Significant Figures
nonzero numbers always significant
zeroes
before never
between always
behind sometimesw/decimal – yesw/o decimal - no
Significant Figures in Calculations
A calculated result can be no more certain than the data measured.
Mathematical operations (pp. 23-24)Averaging least number of decimal places+ and - least number of decimal placesx and ÷ least number of sig. figs.
Round off at the end at the end of a multi-step problem.
Sig. Fig. examples
1.6 Dimensional Analysis
Problem-solving strategies: Estimate and then calculate your answer.
Do the two agree? Get your units correct and your answer
should be correct. Report to correct number of sig. figs. Practice, practice, practice!