ch 1 - matter, energy, and measurements

central science

chemistry is often called the

matter

anything that has mass and takes up space

composition

the kinds of atoms that matter contains

structure

the arrangement of the atoms

macroscopic domain

in the realm of ordinary-sized objects

• observe directly through sight, touch

microscopic domain

too small to be seen - realm of atoms and molecules

• use microscopes to enhance human senses to see/observe. realm of imaginary

symbolic domain

special language of symbols to represent both macroscopic and microscopic domains

• symbols, chemicals formulas

change in identity

chemical symbols describe a chemical change

no change in identity

chemical change describing a physical change

solid, liquid, gas

states of matter

pure substance or a mixture

types of matter

pure substance

matter with distinct properties and composition

• does not vary from sample to sample

• fixed composition, can be represented with a single symbol or formula

• cannot be separated by physical means (only chemical)

element and compound

what are the two types of pure substances

mixture

two or more substances that are not chemically combined

• variable composition

• are separable by physical means such as filtration, distillation, chromatography

homogenous and heterogenous

two types of mixtures

elements

substances that cannot be decomposed into simpler substances

compounds

substances composed of 2 or more different elements, with atoms that are chemically combined

atoms

smallest building blocks of matter. they cannot be decomposed into simpler substances by ordinary chemical reactions

molecule

two or more atoms helps together by chemical bonds

molecule and compound

what is CO2

molecule and element

What is N2

atom and element

What is He?

composition

the number of each atom type present (chemical formula)

structure

the way in which the atoms are bonded together in 3D space

different properties

different structures =

heterogenous mixtures

mixtures that have non uniform composition, properties and appearance. composed of different pure substances

homogeneous mixture

mixtures that are uniform in their properties and composition. composed of different pure substances

solutions

another name for homogenous mixtures

accuracy

degree of reliability of a measurement

• how close the measurements are to the true value

• must compare measured values (average) to true value

• based on the method of instruments used to make measurements

precision

degree of reproducibility of a measurement

• how close the measurements are to one another

• based on the skill of the measurer

• a value with finite number of SF

• a unit

a measure ment always has two things:

significant figures

all certain digits + one estimated place

1. non zero digits are always significant

2. zeroes between two significant figures are significant

3. zeroes at the beginning of a number are never significant

4. zeroes at the end of a number are only significant if a decimal point is written in the number

4 rules of SF

coefficient

contains all significant figure information

exponent

indicates magnitude of the value (infinite sf)

know it yet?

learn how to rewrite numbers into scientific notation with appropriate sf!

rounded to the least significant decimal place

SF in addition and subtraction are ____

rounded to the number of digits that corresponds to the least number of significant figures in any of the numbers used in the calculation

SF in multiplication or division are _____

extensive

properties that depend on the amount of substance present

intensive

properties that do not depend on the amount of substance present, instead depends on Identity

1 cm³

1 mL =

m/v

Density equation

10^-9

Nano (n)

10^-6

Micro (u)

10^-3

Mili (m)

10^-2

Centi (c)

10^-1

deci (d)

10³

Kilo (k)

property

an attribute, quality or characteristic of something

physical state of a sample of matter

example of a property

temperature and pressure of the sample

the observed physical state of a sample of matter depends on ___ and ____

kinetic energy

keeps the molecules moving and apart

attractive forces between the particles

holding the particle to one another

kinetic energy

energy based upon MOTION of an object

potential energy

energy upon POSITION of a an object

sample temperature (thermometer)

the kinetic energy of the different samples is describe by _____

particle position from other particles (attractions)

Potential energy of the different samples is described by ____

Ek = ½ mv²

formula for Kinetic Energy:

Ep= a Q₁Q₂/d

potential energy equation:

repulsion

two positive point charges lead to ____

repulsion

two negative point charges lead to ____

attraction

a negative and positive charge leads to _____

distance decreases and PE increases

bringing two negatively charged particles together

distance decreases and PE decreases

separating two positively charged particles

distance increases and PE increases

breaking a chemical bond (separating two attracted atoms)

distance decreases and PE decreases

forming a chemical bond (bringing together two attracted atoms)

physical change

a change that does not change the identity of the substance

• typically reversible

• often times we are only changing the energy of the sample

chemical change

a change that does change the identity pf the substance

• a chemical reaction

• typically irreversible

chemical

physical or chemical: rusting on the bottom of a car

physical

physical or chemical: cutting a banana into slices

physical

physical or chemical: melting down a gold chain

chemical

physical or chemical: burning a wood log

physical

physical or chemical: chopping a wood log into sticks

physical

physical or chemical: crushing a soda can

physical

physical or chemical: dissolving sugar with hot water

chemical

physical or chemical: caramelizing white sugar in a hot pan

chemical

physical or chemical: growing my hair

filtration

removes solid from a heterogenous mixture

physical

physical or chemical: separation of a mixture

dilution

separates components of a homogenous mixture based on boiling point temperature

chromatography

technique to separate components of a homogenous mixture that contains substances with different tendency to stick to a surface (attractions)

physical properties

determined or measure without changing the identity of the substance

color, odor, melting/boiling point density

example of physical properties:

chemical properties

describe reactions with or conversions into other substances. these properties describe the chemical changes that are possible for a substance

• describe reactivity (ability to undergo chemical reactions