Presentation on theme: "Why study chemistry? 1. It’s required. 2. It sounds interesting. 3. It’s unavoidable. 4. It truly is the central science."— Presentation transcript:
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.
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
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?
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.
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
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 places x and ÷ least number of sig. figs. Round off at the end at the end of a multi- step problem.
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!