Chapter 2:Matter & Change

Matter Anything that has mass &

take up space

Mass = measurement of the amount of matter an object contains

Chemistry = the study of matter & the changes that it undergoes

Classifying Matter

Quantitative – numerical information

how much, how little, how big, how small

Qualitative – descriptive information

condition, color, size, shape, odor, texture

Properties of Matter1. Extensive – a property that depends on the amount of

matter in a sample ex. mass, volume, amount of energy 2. Intensive – a property that depends on the type of

matter in a sample ex. hardness, density, boiling point, electrical

conductivity

Substance – matter that has uniform & unchanging composition

has identical intensive properties… Why? because every sample has the same composition

3. Physical Properties – a characteristic that can be observed or measured w/out changing the identity of a substance

ex. color, odor, taste, hardness, density, melting/boiling points, state of matter

States of Matter – the physical forms in which all matter exists on Earth

Can you identify these 3 states?

Solid def. shape & volume shape

independent of container

particles are packed together

Liquid def. volume shape depends on container particles can move freely

Gas indefinite volume & shape particles move quickly & spread apart

Physical Changes – a change that occurs in the physical appearance of a substance, but does not change its identity

breaking, splitting, grinding, cutting, crushing

Ex. melting, boiling, freezing, evaporating, dissolving, condensing

4. Chemical Properties – relates to a substances ability to undergo changes that transform it into a different substance

easiest to see when a chemical is reacting

Chemical changes – a change that produces matter with a different composition than the original matter

ex. burning, rotting, rusting, reacting, cooking, digestion, respiration

Mixtures A combination of 2 or more types of matter Each component keeps its own identity & properties Components are only physically mixed & can be

separated using physical means

Chicken noodle soup

Cinnamon & Sugar

Air

Types of Mixtures1. Heterogeneous mixture -

a mixture in which the substances are not evenly distributed

Salad

Ice tea with ice

Oil & vinegar

2. Homogeneous mixture –

a mixture or ‘solution’ in which the substances are evenly distributed

Kool-Aid

Water

Stainless Steel

Phase – used to describe any part of a sample with uniform composition & properties

Homogeneous mixture

1 phase

Heterogeneous mixture

2 phases

1. Filtration – a technique that uses a porous barrier to separate a solid from a liquid

Can you think of any common applications?

Separating Mixtures

‘Plays’ on differences in physical properties

2. Distillation – a technique that can be used to physically separate most homogeneous mixtures based on differences in the boiling points of the substances involved

3. Chromatography – a technique that is used to physically separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material

Pure Substances

Every sample has same: characteristic properties composition

Are made of: one type of atom: element

Ex: iron, gold, oxygen

2 or more types of atoms: compound Ex: salt, sugar, water

Which are pure substances?

Element Simplest form of matter that has its own unique

set of properties Can not be separated into simpler substances

by physical or chemical means Each element is made up of a single type of

atom

ex. hydrogen, nitrogen, lead

Compound A substance that contains 2 or more elements

chemically combined in a fixed proportion Properties are different than the individual

elements

ex. Glucose (sugar)

Glucose – sweet, white solidCarbon – black, tasteless solidOxygen – colorless, tasteless gas Hydrogen – colorless, tasteless gas

Breaking Down Compounds Physical methods do not work Recall…

Chemical changes – a change that produces matter with a different composition than the original matter

Substances vs. Mixtures

Symbols & Formulas Chemical Symbol

each element is represented by a one- or two-letter symbol

Trends:1st letter = always capitalized2nd letter = always lowercaseSubscripts = indicate the relative proportions of the elements

in a compound

H K Au H2O C6H12O6

Hydrogen Potassium Gold Water Glucose

Chemical Reactions The process by which the atoms of one or more

substances are rearranged to form different substances

Occurrence can be indicated by changes in temperature, color, odor, & physical state

Also known as a chemical change Chemical properties can only be observed when

a substance undergoes a chemical change

The process of photosynthesis is a chemical reaction in which light energy, carbon dioxide and water, are transformed to create glucose and oxygen.

The photosynthetic chemical reaction can be shown by writing out the element symbols for each compound.

Reactants substances to the left of the arrow ‘ingredients’ CO2 and H2O

Products substances to the right of the arrow ‘what is made’ or produced C6H12O6 and O2

Recognizing Chemical Changes

1. Transfer of energy

Energy may be given off

in the form of heat or light

2. Change in color

Substances may

‘brown’

Indicators

How can you tell whether a chemical change

has taken place?

3. Precipitate

A solid that settles

out of a liquid mixture

4. Gas production

Indicated by the formation

of ‘gas bubbles’

Conservation of Matter During any chemical reaction, the mass of the

products is always equal to the mass of the reactants

+ O2

+ CO2 + H2O vapor

Conservation of mass also applies to physical changes…

10g of ice 10g of liquid H2O

Law of Conservation of Mass In any physical or chemical change, mass

is conserved i.e. Mass is neither created or destroyed