Download chemical change

Cornell Notes Paper
Topic: Changes in Matter
Date: 11/6/14
Source: ItC, 20-27
Main Topics
Detailed Notes
What happens to a substance
in a physical change?
 Physical change – alters the form or appearance of
matter but does not turn any substance in the matter
into a different substance (example – butter turned into
a sculpture looks different but is still butter, snow
melting)
 changes of state are physical changes – ice into water,
water into water vapor, water turning into ice…the
water looks different but is not a new material
 sugar water – when dissolved, sugar disappears but no
new substance is created. When water evaporates,
sugary crust is left in the pan – dissolving is a physical
change
 other physical changes – bending, crushing, breaking,
and chopping
 any change that alters only the shape or form of matter
is a physical change
 methods of separating mixtures – filtration, distillation
(both are physical changes)
What happens to a substance
in a chemical change?
 chemical change – a change in matter that produces
one or more new substances
o ex - a single substance breaking down into two or
more other substances (hydrogen peroxide
breaking into water and oxygen)
o ex - two or more substances combine to form
different substances (photosynthesis – several
compounds combined with energy, produce new
substances)
o ex - vapors from glue react with sweat/body
chemicals to form a white powder
o ex – Luminol reacts with blood – creates a new
substance that glows in the dark
Cornell Notes Paper
Topic: Changes in Matter
Main Topics
Examples of chemical change
Conservation of mass
(the law of conservation of
mass (LoCoM)
How are changes in energy
and matter related?
Date: 11/6/14
Source: ItC, 20-27
Detailed Notes
 ex - burning of natural gas on a stove. When burned,
methane combines with oxygen in the air to create
carbon dioxide and water vapor. Both substances
have different properties than methane.
 Other processes that result in chemical changes –
o combustion - rapid combining of fuel with
oxygen – creates heat, light, new substances
o electrolysis – electricity breaks compounds
into elements or simpler compounds – ex.
breaking water into hydrogen and oxygen
o oxidation - combining a substance with
oxygen – when iron rusts
o tarnishing - combining of bright metal with
sulfur – creates dark coating on metal –
tarnishing of brass
 LoCoM - matter is not created or destroyed in any
chemical or physical change
 ex - figure 5 on page 25 – new substances created,
but same atoms are simply rearranged
 Energy = the ability to do work or cause change
 KEY CONCEPT – every chemical and physical change
in matter includes a change in energy!
o Bending a paperclip takes energy
o ice melting absorbs energy from surrounding
matter
o candle wax burning gives off energy as light
and heat
 *** Like matter, energy is conserved in a chemical
change – it is never created or destroyed – can only
be transformed from one type to another
Cornell Notes Paper
Topic: Changes in Matter
Main Topics
Temperature and thermal
energy
Transforming chemical
energy
Date: 11/6/14
Source: ItC, 20-27
Detailed Notes
 Temperature – measure of how hot or cold something
is
 Thermal energy – total energy of the motion of all of
the particles in an object – thermal energy flows from
warmer to cooler matter
o ex - particles moving quickly bang into particles
nearby in a chain reaction
 Temperature and thermal energy are not the same
thing! But they are related.
 Thermal energy is released or absorbed when matter
changes – ex. ice absorbs thermal energy from its
surroundings when it melts leaving the surroundings
feeling cold
 endothermic change – a change in which energy is
absorbed (melting of ice)
 exothermic change – change in which energy is
released (combustion)
 Chemical energy – energy stored in the chemical bonds
between atoms
o CE is stored in foods, fuels, cells of your body –
we gain CE from the foods we eat
o burning fuel transforms CE and releases it as
thermal energy
o energy can change into other forms of energy