College Chemistry Ch1

Methods and measurement

Chemistry

the study of matter and the changes it undergoes

Matter

Anything that has mass and takes up space

Roles of Chemistry

Public health, pharmaceutical industry, food, science, forensic sciences, medical practitioners

Scientific Method

Observation, formulation of a question, pattern, recognition, develop series, experimentation, summarize information

Properties

characteristics used to describe different types of matter

Ways to categorize matter

1. by state

2. by composition

Three states of matter

solid, liquid, gas

Pure substance

A substance made of only one kind of matter and having definite properties.

Mixture

A combination of two or more pure substances that are not chemically combined

Element

A pure substance made of only one kind of atom

Compound

A substance made up of atoms of two or more different elements joined by chemical bonds

Homogeneous

Uniform composition, particles, well, mixed, thoroughly intermingled

Heterogeneous

Non-uniform composition, random placement

physical property

Observed, without changing the composition or identity of a substance

physical change

Produces a recognizable difference, in appearance of a substance without causing any change in its composition or identity (state change)

chemical property

Resulting in a change in composition, and can be observed only through a chemical reaction

Chemical reaction (change)

A chemical substance is converted into one or more different substances by rearranging, removing, replacing or adding atoms (H2+O= H2O)

intensive property

A property of matter, that is independent of the quantity of the substance (ex: color and melting point)

extensive property

A property of matter that depends on the quantity of the substance (ex: mass and volume)

Units

standard quantities used to specify measurements

Metric system

The decimal measuring system based on the meter, liter, and gram as units of length, capacity, and weight or mass.

English system

measurement system used for everyday measurements in the United States.

Mass

A measure of the amount of matter in an object

Length

Distance between two points

Volume

Amount of space occupied by an object

Time

Metric measurement unit is second (s)

significant figures

All the digits that can be known precisely in a measurement, plus a last estimated digit (information bearing numbers)

scientific notation

a method of expressing a quantity as a number multiplied by 10 to the appropriate power

Accuracy

The degree of agreement between the true value and the measured value

Error

The difference between the true value, and an estimation (random or systematic)

Precision

A measure of agreement of replicate measurements

Deviation

Amount of variation present in a set of replicate measurements

Temperature

The degree of hotness of an object

Temperature conversions

T°c=T°f-32/1.8

T°f=1.8xT°c+32

T°f —> T°c

Kelvin

Tk= T°c+273.15

Energy

the ability to do work

Kinetic energy

energy of motion

Potential energy

stored energy that results from the position or shape of an object

Joules

1calorie (cal)= 4.18 joules (J)

1 calorie (cal)

1 kcal=1 Cal =1000 cal

Concentration

The number or mass of particles of a substance contained in a specific volume

Density

D=m/v

specific gravity

=density of object (g/mL) / density of water (g/mL)