Chapter 1 Study Guide

-example 1.2 pg 5 top paragraph

matter

Made of individual atoms

• have to be seen through STM

Scanning Tunneling microscope (STM)

uses an electrical current from a tiny needle to probe the surface of the substance

atoms are connected by “bridges”

electrons that interconnect

macroscopic world

• the world of cars, tables, and rocks

• The main job of scientists is to delve into the macro world and discover its “parts”

• example: sand on beach (solid substance, individual grains, silicon and oxygen)

microscopic world

made of atoms and molecules

• have to find the connection between both worlds

• have to think on the atomic level

variety of sustances

• Made up of only 100 atoms

• The way the atoms are organized in a given substance determines the properties of the substance

water

• most common and important substances on Earth

• composed of 2 atoms: (2) hydrogen and (1) oxygen

electrical current effect on water

• water is decomposed to hydrogen and oxygen

• the chemical elements themselves exist naturally as diatomics (2 atom) molecules

• it takes 2 molecules of water to furish the right number of oxygen and hydrogen atoms to allow for the formation of 2-atom molecules

• O= O₂

• H=H₂

decomposition of water

2H₂O -(electrical current)→ O₂ and 2H₂

• car uses a spark=opp way

2 fundamental concepts of chemistry

• Matter is composed of various types of atoms

• one substance changes to another by reorganizing the way the atoms are attached to each other

Scientific Method: This process contains the fundamental elements of science

• making observations (collecting data)

• suggesting a possible explanation (formulating a hypothesis)

• doing experiments to test the hypothesis

chemists

• really good problem-solving skills

science

• The framework for gaining and organizing knowledge

• plan of action: a procedure for processing and understanding certain types of information

observations

(qualitative/quantitative)

• can be witnessed and recorded

quantitative

measurement (# + un.)

theory/model

is a set of tested hypotheses that gives an overall explanation of some natural phenomenon

• interpretation or attempt to explain why something happened

• change as more people become available

• can change over time as questions never stop being asked; can be refined or replaced

• accepted theory=used for performing a new experiment

• human invention or educated guess

natural law

Such generally observed behavior is formulated into a statement

• a law summarizes what happens

law of conservation of mass

The observation that the total mass of materials is not affected by a chemical change in those materials

non-ideal scientific method

coupling of observations and hypotheses

• we tend to see what we expect to see and often fail to notice things that we don’t expect to see

• important to remember that scientists are human so there will be some bias

Galileo

was forced to recant his astronomical observations in the face of strong religious resistance

Lavoisier

father of modern chemistry, was beheaded b/c of his political affiliations.

progress of sciences

affected more by human frailties and our institutions than by the limits of science

2 systems of standardized units

1. English system (US)

2. Metric system (world)

International System (SI)

1960, this system is based on the metric system and units derived from the metric system

mass (fundamentals)

kg

length

m

time

s (sec)

temp

K

electric current

A (ampere)

amount of a substance

mol

luminous intensity

cd (candela)

tera (prefix)

• T

• 10¹²

giga

• G

• 10⁹

mega

• M

• 10⁶

kilo

• k

• 10³

hecto

• h

• 10²

deka

• da

  • 10

why use a prefix?

b/c the fundamental units are not always convenient(expressing the mass of a pin in kg is awkward), prefixes are used to change the size of a unit

volume

• uses length to find

• a cube that measures 1m on each side=1m³

decimeters (dm)

10 in a meter

• volume of the cube is 1m³ = 10dm³

cubic decimeter

• equals a liter and 10cm

• 1L=1dm³=10cm³=1000cm³

1cm³=1mL

1L=1000cm³=1000mL

common types of lab equipment used to measure liquid volume

• 100mL graduated cylinder

• 25mL pipet

• 50mL buret

• 250mL volumetric flask

mass

is a measure of the resistance of an object to a change in its state of motion.

• is measured by the force necessary to give an object a certain acceleration

weight

use the force that gravity exerts on an object to measure its mass

• response of mass to gravity, it varies with the strength of the gravitational field

buret

• 20.15mL shown=amount used

• Have to infer, but 0.1mL difference (meniscus)

• Last # is estimated (can change from person to person)

certain digits

the results show that the first 3 numbers remain the same regardless of who make the measurement

uncertain digit

The digit to the right of the certain digits (estimated)

• A measurement will always have some degree of uncertainty

uncertainty depends on

the precision of the measuring device

• want it to occur in later places

significant figures

certain digits + 1st uncertain digit

• last # is an assumed ± 1

• ex: 1.86 ± 0.01

25.00mL sample from a pipet and a 25mL graduated cylinder to measure 25mL, what’s the difference between them?

25mL mean between 24-26, whereas 25.00 mL means 24.99-25.0. The pipet shows much greater precision than the graduated cylinder does.

accuracy

refers to the agreement of a particular value with the true value

precision

refers to the degree of agreement among several measurements of the same quantity

• reproducibility

random error/indeterminate error

means that a measurement has an equal probability of being high or low.

• this type of error occurs in estimating the value of the last digit of a measurement

systematic error/determined error

this type of error occurs in the same direction each time; it is either always high or low

• precise measurements will avg out to be accurate only in the SE is absent

rules for counting sig figs

• nonzero integers=sig figs

• zeros

  • leading zeros= not sig figs

  • captive zeros= (between) sig figs

  • trailing zeros=sig figs (not if with decimal pt or exponential notation)

  • exact numbers=inf. sig figs

exponential notation

• the # of sig figs are easy to find

• less writing

example: (sig figs) 0.0105,0.050080,8.050 × 10^-3

• 3

• 5

• 4

rules for sig figs in math operations

• multiplication/division: use the least precise measurement (1.4) (same sig figs)

• add/subtract: the same # of decimal places as the least precise

example: 1.05×10^-3/6.135,21-13.8,2.560×8.8/275.15

• 1.05 ×10^-3

• 7

• 8.2

R=PV/T

r=gas constant

v=volume

p=pressure

t=temp

questions to ask when solving problems

1. what is my goal/where am I going

2. where am I starting/What do I know

3. how do I get there

unit factor method/dimensional analysis

used to convert a given result from one system of units to another (english-metric)

1m

1.094yd

2.54cm

1in

1kg

2.205lb

453.6g

1lb

1L

1.06qt

1ft³

28.32L

unit factor

conversions of length,mass, and volume in the form of an expression

• using the unit factor will never change its value

example: 2.85cm to in

2.85cm x 1in/2.54cm= 2.85/2.54 (in)=1.12in

example:7.00in to cm

(7.00)(2.54)=17.8cm

equivalence statement

1in to 2.54cm

example: 25.5in to cm

(25.5)(2.54)=64.8cm

example: 10.0km to miles

1km=1000m

1m=1.094yd

1760yd=1mi

(10.0)(1000)(1.094)/1760=6.22mi

example: 55mi/h to km/h

(55)(1760)/1.094/1000=88

example:15 km/L to mi/gal

15×1000×1.094/1760/1.06×4=35