chapter 2: matter & change. matter anything that has mass & take up space mass = measurement...
TRANSCRIPT
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