accuracy – the degree of closeness of measurements of a quantity to that quantity’s true value. ...

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Transcript of accuracy – the degree of closeness of measurements of a quantity to that quantity’s true value. ...

accuracy – the degree of closeness of measurements of a quantity to that quantity’s true value.

buoyancy - the tendency or capacity to remain afloat in a liquid or rise in air or gas colloid – heterogeneous mixture with small particles that hang in the mixture compressibility – the ability to move (or squeeze) particles closer together dimensional analysis – a tool to find relationships between quantities using their

dimensions, or units extensive property – properties not inherent to matter itself, and dependent on the

amount of matter present heterogeneous mixture – a mixture of pure substances that is not the same throughout homogeneous mixture – a mixture of pure substances that is the same throughout intensive property – properties inherent to matter itself, and independent of the amount

of matter present precision – the degree which repeated measurements show the same results. scientific notation – a way of writing numbers that are too large or small to use

conventional decimal notation significant figures (sig. figs) – digits in a number that carry meaning contributing to its

precision suspension – heterogeneous mixture with large particles that settle to the bottom. Tyndall effect – light scattering by particles in a colloid viscosity – the measure of a resistance of fluid to flow; “thickness” of a liquid

All matter shares two specific characteristics All matter has mass All matter takes up space

All matter takes one of two basic forms Pure Substance – element or compound Mixture – homogeneous or heterogeneous

• Elements• Matter consisting only of atoms of the same

element

• Compounds• Matter consisting of atoms of different

elements chemically bonded to each other

Homogeneous Mixture

Heterogeneous Mixture

Separation of Mixtures – All mixtures are created by a physical process of mixing and can also be separated by some physical means

A mixture of pure elements that is the same throughout

All samples taken will provide the same proportion of pure substances within that mixture

Also known as a solution

A mixture of pure elements that is not the same throughout

Proportions of pure substances within the mixture are not the same in all samples

Includes colloids and suspensionsColloid – Heterogeneous mixture with small

particles that hang in mixtureSuspension – Heterogeneous mixture with large

particles that settle

Compounds Mixtures

All matter has one chemical structure

Matter has at least two pure substances

Making a compound involves a chemical process of combining elements

Making a mixture involves a physical process of combining elements and compounds

Separating a compound into elements involves a chemical process

Separating a mixture into pure substances involves one or more physical processes

Has a definite proportion by mass

The proportion of pure substances is variable

Pure SubstancesElements cannot be separated.

Compounds can only be separated through some form of chemical reaction.

MixturesAll mixtures are created by a physical process of mixing and can also be separated by physical means

Skimming – Using an instrument to remove floating material from a mixture

Decanting – Pouring off liquid to separate it from solid material at the bottom of the container

Filtering – Using a filter to separate material based on the size of particles

Distillation – Using heat to remove liquid from a mixture leaving behind solid material (evaporation) or a liquid with a very different boiling point (fractional distillation)

Magnetism – Using a magnet to separate magnetic substances from non-magnetic substances

Centrifuging – Using rotational motion to separate substances by mass

All matter can be described through a combination of characteristics called properties

There are two categories of propertiesPhysicalChemical

Descriptions of properties Intensive properties – properties inherent to the

matter itself independent of the amount of the matterExtensive properties – properties not inherent to

matter itself and dependent on the amount of matter present

A combination of intensive and extensive properties that can be observed without changing the substance itself

Describe the size, shape, appearance, amount, and physical attributes of the matter

Examples: Intensive– state of matter, melting point, boiling point,

density, color, crystalline structure, conductivity, malleability, ductility

Extensive– mass, volume, shape, texture, colligative properties

Intensive physical property of matter

States of matter:Solid

Liquid

Gas

Plasma – not discussed in this class

Particles are tightly packed

Particles can only vibrate in place

Rigid form of matter

Definite shape and volume

Generally the most dense state of matter

Least compressible

Particles are close together

Particles flow freely past each other

Definite in volume, but not in shape (takes the shape of its container)

Generally less dense than solids, more dense than gas

Much less compressible than gas, slightly more compressible than solid

Particles fly apart

Particles fully occupy the volume of the container

No definite shape and no definite volume

Generally the least dense state of matter

Most compressible

The ability to move (squeeze) particles closer together

The closer the particles are before attempting to move them, the less the particles can move Examples: particles of solids are very close

together and cannot move nearly as far as particles of gases that start out much further apart

Any change in matter that is accomplished without changing the substance into a new substance

The substances present before and after the change are of the same chemical structure as they were before the change

Includes any change to the size, shape, or state of the matter changed

Do not get confused by the words ice, water, and steam – melting, freezing, condensing, or evaporating water are physical changes – the chemical composition is not changed

Intensive physical property that measures of how tightly packed matter is

Directly related to the mass of matter and inversely related to the volume (both of which are extensive properties)

Formula: Density = Mass / Volume

Mass is measured in grams and volume for solids and liquids are generally measured in cm3 (mL) or L (Liters)

All chemical properties are intensive

Chemical properties can only be observed by changing the matter itself

Examples: reactivity, combustibility, ionization energies, electronegativity, electron affinity, corrosiveness

Any change in matter that produces a new substance

Always involves a chemical reaction

Involves a re-arrangement of the atoms present before the change