CHEMISTRY-CONCEPTS-Science.CHEM .ppt

CHEMISTRY-CONCEPTS-Science.CHEM

1. 1
Matter and Energy

2. 2
Properties
•Characteristics of the substance under
observation
•Properties can be either
directly observable or
the manner something interacts with other
substances in the universe

3. 3
Universe Classified
•Matter is the part of the universe that
has mass and volume
•Energy is the part of the universe that
has the ability to do work
•Chemistry is the study of matter
–The properties of different types of matter
–The way matter behaves when influenced
by other matter and/or energy

4. 4
Properties of Matter
•Physical Properties are the characteristics of
matter that can be changed without changing its
composition
–Characteristics that are directly observable
•Chemical Properties are the characteristics that
determine how the composition of matter changes
as a result of contact with other matter or the
influence of energy
•Characteristics that describe the behavior of
matter

5. 5
Classify Each of the following as
Physical or Chemical Properties
The boiling point of ethyl alcohol is 78°C.
Diamond is very hard.
Sugar ferments to form ethyl alcohol.

6. 6
Classify Each of the following as
Physical or Chemical Properties
The boiling point of ethyl alcohol is 78°C.
–Physical property – describes inherent characteristic
of alcohol – boiling point
Diamond is very hard.
–Physical property – describes inherent characteristic
of diamond – hardness
Sugar ferments to form ethyl alcohol.
–Chemical property – describes behavior of sugar –
forming a new substance (ethyl alcohol)

7. 7
•solid, liquid, gas
States of Matter
StateShape VolumeCompress Flow
SolidKeeps
Shape
Keeps
Volume
No No
LiquidTakes
Shape of
Container
Keeps
Volume
No Yes
Gas Takes
Shape of
Container
Takes
Volume of
Container
Yes Yes

8. Liquid water
takes the
shape of its
container.

9. 9
Changes in Matter
•Physical Changes are changes to matter that
do not result in a change the fundamental
components that make that substance
–State Changes – boiling, melting, condensing
•Chemical Changes involve a change in the
fundamental components of the substance
–Produce a new substance
–Chemical reaction
–Reactants  Products

10. 10
Classify Each of the following as
Physical or Chemical Changes
Iron metal is melted.
Iron combines with oxygen to form rust.
Sugar ferments to form ethyl alcohol.

11. 11
Classify Each of the following as
Physical or Chemical Changes
Iron is melted.
–Physical change – describes a state change, but the
material is still iron
Iron combines with oxygen to form rust..
–Chemical change – describes how iron and oxygen
react to make a new substance, rust
Sugar ferments to form ethyl alcohol.
–Chemical change – describes how sugar forms a new
substance (ethyl alcohol)

12. 12
Elements and Compounds
•Substances which can not be broken down
into simpler substances by chemical reactions
are called elements
•Most substances are chemical combinations
of elements. These are called compounds.
–Compounds are made of elements
–Compounds can be broken down into elements
–Properties of the compound not related to the
properties of the elements that compose it
–Same chemical composition at all times

13. 13
Classification of Matter
•Homogeneous = uniform throughout, appears to be one
thing
–pure substances
–solutions (homogeneous mixtures)
•Heterogeneous = non-uniform, contains regions with
different properties than other regions
Pure Substance
Constant Com position
Hom ogeneous
M ixture
Variable Com position
M atter

14. 14
Pure Substances vs. Mixtures
•Pure Substances
–All samples have the same physical and chemical properties
–Constant Composition  all samples have the same
composition
–Homogeneous
–Separate into components based on chemical properties
•Mixtures
–Different samples may show different properties
–Variable composition
–Homogeneous or Heterogeneous
–Separate into components based on physical properties
•All mixtures are made of pure substances

15. 15
Identity Each of the following as a
Pure Substance, Homogeneous
Mixture or Heterogeneous Mixture
Gasoline
A stream with gravel on the bottom
Copper metal

16. 16
Identity Each of the following as a
Pure Substance, Homogeneous
Mixture or Heterogeneous Mixture
Gasoline
–a homogenous mixture
A stream with gravel on the bottom
–a heterogeneous mixture
Copper metal
–A pure substance (all elements are pure substances)

17. 17
Separation of Mixtures
•Separate mixtures based on different physical
properties of the components
–Physical change
EvaporationVolatility
ChromatographyAdherence to a Surface
FiltrationState of Matter
(solid/liquid/gas)
DistillationBoiling Point
TechniqueDifferent Physical Property

18. 18
Energy and Energy Changes
•Capacity to do work
–chemical, mechanical, thermal,
electrical, radiant, sound, nuclear
•Energy may affect matter
–e.g. raise its temperature, eventually
causing a state change
–All physical changes and chemical
changes involve energy changes

19. 19
Heat
•Heat: a flow of energy due to a temperature
difference
1.Exothermic = A process that results in the
evolution of heat.
•Example: when a match is struck, it is an
exothermic process because energy is produced as
heat.
2.Endothermic = A process that absorbs energy.
•Example: melting ice to form liquid water is an
endothermic process.

20. 20
Units of Energy
•One calorie is the amount of energy needed to
raise the temperature of one gram of water by 1°C
–kcal = energy needed to raise the temperature of 1000 g
of water 1°C
•joule
–4.184 J = 1 cal
•In nutrition, calories are capitalized
–1 Cal = 1 kcal

21. 21
Energy and the Temperature of
Matter
•The amount the temperature of an object
increases depends on the amount of heat
added (Q).
–If you double the added heat energy the
temperature will increase twice as much.
•The amount the temperature of an object
increases depends on its mass
–If you double the mass it will take twice as much
heat energy to raise the temperature the same
amount.