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 11 th

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 O 2, H 2 O, CO 2, C 2 H 5 OH, C 2 H 6 O 2, C 9 H 8 O 4 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

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 m

Temperature Scales

Temperature Conversions °F → °C °C → °F °C → K

Density Density – mass per unit volume D = m/V (g/cm 3 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.

Density of Water

Calculate the volume (in mL) of 87.6 g of platinum. (D Pt = 21.5 g/cm 3 )

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 numbersalways significant zeroes beforenever betweenalways behindsometimes w/decimal – yes w/o decimal - no

Significant Figures in Calculations A calculated result can be no more certain than the data measured. Mathematical operations (pp ) Averaging least number of decimal places + and -least number of decimal places x 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!