Ch 2 Section 2 Flashcards Preview

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Flashcards in Ch 2 Section 2 Deck (59):
1

Measurements represent

Quantities

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A quantity is something that has

Magnitude, size, or amount

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Quantity is not the same as a

Measurement

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Units of measurement compare

What is to be measured with a previously defined size

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Nearly every measurement is a

Number plus a unit with choice of unit depending on quantity being measured

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SI

Le systéme international d'Unités
Measurement system agreed on by scientists all over the world

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SI system adopted in

1960 by General Conference on weights and measures

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SI has

7 base units with most other units derived from these 7

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SI units are defined in terms of

Standards of measurement

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Standards are objects or natural phenomena that are of

Constant value
Easy to preserve and reproduce
Practical on size

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Numbers are written in a form that is

Agreed upon internationally

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Prefixes added to names of SI units represent

Quantities that are larger or smaller than the base units

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Centi

1/100

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1 cm

1/100 of a meter

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SI standard unit for mass is

Kilogram

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Gram

1/1000 of a kg

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Gram is more

Useful for measuring masses of Small objects

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For even smaller objects (measuring mass)

Milligram is used

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1 mg

1/1000 of a gram

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Mass is determined by

Comparing mass of an object with a set of standard masses that are part of the balance

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Measurements are

Quantitative information.

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Weight is a measure of the

Gravitational pull on matter

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Weight is typically measured on a

Spring scale

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As the force of gravity on an object increases

Weight increases

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SI standard unit for length is

Meyer

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1 km

1000 m

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To express shorter distances the

Cm is often used

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Combinations of SI units form

Derived units

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Derived units are produced by

Multiplying or dividing standard units

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Pascal

kg/ m x s^2

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Prefixed can also be added to express

Derived units

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Volume is the amount of

Space occupied by an object

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Derived SI unit of volume is

m^3

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One m^3=

Volume of a cube whose edges are 1 m long

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The cm^3 is often used to

Express the volume of materials in a chem lab

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m^3=

1000000 cm^3

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When chemists measures volumes of liquids and gases they often use

A non SI unit called the liter

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Liter=

1 decimeter cubed

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1 liter =

1000 cm cubed

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1000 mL=

1 L

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mL and cm^3 are

Interchangeable

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Density

Ratio of mass to volume
Mass/volume

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SI unit for density is derived from

Base units for mass and volume- kg and m^3- and can be expressed as
kg/m^3

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Density is often expressed as

g/ cm^3 it g/mL

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Densities of gas are generally expressed as

kg/m^3 or g/L

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Density is a characteristic

Physical property of a substance

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Density doesn't depend on the size of the same because

As the samples mass increases, it's volume increases proportionately, and the ratio of mass to volume is constant

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Density can be used as

A property to help identify a substance

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Density varies with

Temperature

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Most objects expand as temperature increases thereby

Increasing in volume

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Density usually

Decreases with increasing temperature

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A conversion factor is a

Ratio derived from the equality between two different units that can be used to convert from one unit to the other

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Each conversion factor equals 1 because the

2 quantities divided in any conversion factor are equivalent to each other

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Because conversion factors are equal to 1 they can be multiplied by other factors in equations

Without changing the validity of the equations

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Dimensional analysis

Mathematical technique that allows you to use units to solve problems involving measurements

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Quantity sought =

Quantity given x conversion factor

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It is always best to begin with an idea

Of the units you will need in your final answer

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Conversion factors can be derived if you know the

Relationship between the unit you have and the unit you want

59

1 m

10 decimeters