Chapter 3 The Driving Forces Exothermic & Endothermic Entropy.
DESCRIBE PHYSICAL & CHEMICAL CHANGES IN TERMS OF ENDOTHERMIC & EXOTHERMIC PROCESSES COS 5.0.
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Transcript of DESCRIBE PHYSICAL & CHEMICAL CHANGES IN TERMS OF ENDOTHERMIC & EXOTHERMIC PROCESSES COS 5.0.
DESCRIBE PHYSICAL & CHEMICAL CHANGES IN
TERMS OF ENDOTHERMIC & EXOTHERMIC PROCESSES
COS 5.0
WHAT YOU’LL LEARN• Explain the relationship between, matter atoms & elements• Categorize materials as pure substances or mixtures• Identify elements & compounds• Perform calculations involving density• Compare & Contrast physical & chemical properties• Determine how the law of conservation of mass applies to chemical changes• Compare & Contrast physical & chemical changes• Describe how to detect whether a chemical change has taken place.• Describe the four common states of matter.• List the different changes of state & describe how particles behave in each
state• Describe differences between endothermic & exothermic reactions
MATTER
COMPOSITIONMATTER
anything that has mass and takes up space (volume)
ATOMSsmallest particle of an element that has same properties of element
MOLECULES smallest unit of a substance that keeps all of physical and chemical properties of that substance.Two or more atoms that are chemically bonded
CLASSIFICATION
PURE SUBSTANCEPURE SUBSTANCE
• sample of matter, either a single sample of matter, either a single element or a single compound, that has element or a single compound, that has definite chemical and physical definite chemical and physical propertiesproperties
ELEMENTSELEMENTS
• substance that cannot be separated or broken down substance that cannot be separated or broken down into simpler substances by chemical meansinto simpler substances by chemical means
• Can be found as solids, liquids, or gasesCan be found as solids, liquids, or gases• Found on periodic tableFound on periodic table• Made of identical atomsMade of identical atoms• Pure substancesPure substances• Represented by abbreviations/symbols consisting Represented by abbreviations/symbols consisting
of one or two lettersof one or two letters• Examples: H, N, S, O, P, Au, Hg, NaExamples: H, N, S, O, P, Au, Hg, Na
COMPOUNDS
• substance made of atoms of two or more different elements that are chemically combined
• they always combine in same proportions.• Can be broken down through chemical means• Pure substances• Every compound is different from the
elements it contains.
CHEMICAL FORMULAS
• combo of chemical symbols and numbers to represent a substance.
• Subscript• represents number of atoms • located lower right of chemical
symbol
• Examples: NO2, NH3, NaCl, C6H6O6
MIXTURES• two or more substances that are NOT chemically
combined.• Variable composition• Each components retains their characteristic
properties• May be separated into pure substances by physical
methods• classified by how thoroughly the substances mix.• Two types
HOMOGENEOUS
may be pure substances or solutionsPure substances may be compounds or elementssubstances are evenly distributed “well mixed” Look/have the same composition throughout Particles are small and not easily recognizedcan be separated by physical means (dissolution, centrifuge, gravimetric filtering, etc.). Examples: milk, yogurt
HETEROGENEOUS
made of more than one kind of substance.substances aren’t mixed uniformly “least mixed”different particles in mixtures are large enough to be seeneasily separated by physical means (ie. density, polarity, metallic properties).
Matter Flowchart
MATTER
Can it be separated by physical means?
Homogeneous Mixture
(solution)
Heterogeneous Mixture Compound Element
MIXTURE PURE SUBSTANCE
yes no
Can it be decomposed by chemical means?
noyesIs the composition uniform?
noyes
PROPERTIES OF MATTER
PHYSICAL PROPERTIESPHYSICAL PROPERTIES
• characteristic of matter that can be directly characteristic of matter that can be directly observed without changing identity of observed without changing identity of substancesubstance
• you can see, such as color, shape, hardness, you can see, such as color, shape, hardness, and textureand texture
• easily measuredeasily measured
MASS
• amount of matter in an object• SI Unit: G r a m s (g)
WEIGHT
measure of pull of gravity on an object
SI Unit: N e w t o n s (N) Formula: W = m g
VOLUME
amount of space taken up by an object .
SI Unit: L i t e r s (L).
DENSITY
• mass per unit of volume
• Formula: Density = mass/volume
D = MV
D
M
V
Density1. An object has a volume of 825 cm3 and a density
of 13.6 g/cm3. Find its mass.
GIVEN:
V = 825 cm3
D = 13.6 g/cm3
M = ?
WORK:
M = DV
M = (13.6 g/cm3)(825cm3)
M = 11,220 g
DM
V
Density
2. A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid?
GIVEN:
D = 0.87 g/mL
V = ?
M = 25 g
DM
V
WORK:
V = M D
V = 25 g
0.87 g/mL
V = 28.7 mL
Density
3. You have a sample with a mass of 620 g & a volume of 753 cm3. Find density.
GIVEN:
M = 620 g
V = 753 cm3
D = ?
DM
V
WORK:
D = M V
D = 620 g
753 cm3
D = 0.82 g/cm3
Let’s Try Some More Density Problems
Density
1. If the mass of a rock is 500 g and its volume is 25 cm3, what is its density?
GIVEN:
M = 500 g
V = 25 cm3
D = ?
DM
V
WORK:
D = M V
D = 500 g
25 cm3
D = 20 g/cm3
Density
2. If the density of a liquid is 1.2 g/ml and its volume is 10 ml, what is its mass?
GIVEN:
V = 10 ml
D = 1.2 g/ml
M = ?
WORK:
M = DV
M = (1.2 g/ml)(10 ml)
M = 12 g
DM
V
Density
3. If Bob’s mass is 80 kg and his density is 1.6 kg/l, what is his volume?
GIVEN:
D = 1.6 kg/l
V = ?
M = 80 kg
DM
V
WORK:
V = M D
V = 80 kg
1.6 kg/l
V = 50 mL
BOILING POINT
• temperature and pressure at which a liquid becomes a gas
• liquid is still the same substance
MELTING POINTMELTING POINT
• temperature and pressure at which a solid becomes a liquid
VISCOSITYVISCOSITY
• resistance (difficulty) of a liquid to flow easily
• How “thick” or “thin” a liquid is
• high viscosity: Honey, motor oil, corn syrup
• low viscosity: water, milk, soda
CONDUCTIVITY
• ability to conduct heat or an electric current• High conductivity: metals (copper,
aluminum…)• Low conductivity: wood, rubber, plastic
MALLEABILEMALLEABILE
Ability to be hammered into a thin Ability to be hammered into a thin sheet.sheet.
DUCTILEDUCTILE
• Ability to be drawn into a thin wireAbility to be drawn into a thin wire
CHEMICAL PROPERTIESCHEMICAL PROPERTIES
• describes how a substance can change describes how a substance can change or react to form new substances. or react to form new substances.
FLAMMABILITYFLAMMABILITY
• ability of a substance to react in presence of oxygen and burn when exposed to a flame
REACTIVITY
• how easily a chemical reacts with other substances.
CHANGES OF MATTER
LAW OF CONSERVATION OF MATTER
• matter cannot be created nor destroyed.• It is just converted from one form to
another
SOLIDS SOLIDS Have a definite Have a definite
shapeshape Have a definite Have a definite
volumevolume Least amount of Least amount of
movement of movement of particles.particles.
Particles arranged Particles arranged in a regular pattern in a regular pattern and tightly packed.and tightly packed.
LIQUIDS• Have an indefinite
shape• Have a definite
volume• will assume the
shape of its container.• Particles are close
together but move about freely.
GASES
• Have an indefinite shape
• Have an indefinite volume
• Can fill any container
PLASMA
most common form of matter. makes up over 99% of the visible
universe dangerous, very high energy
(found in stars)
ENDOTHERMIC/EXOTHERMIC REACTIONS
Endothermic = heat energy is absorbed, cools surroundings
Exothermic = heat energy is released, warms surroundings
PHYSICAL CHANGES substance changes state but does not change
its chemical composition. Type of matter remains the same example: water freezing into ice, cutting a
piece of wood into smaller pieces
DISSOLVING
• to disintegrate, break up, or disperse• When a substance dissolves, the
molecules of the substance do not change.
Ways of Dissolving:• solid in a liquid,• gas in a liquid• liquid in a liquid
MELTING
to become altered from a solid to a liquid state usually by heat
endothermic ice cubes melting
BOILING
Change of a substance from a liquid to a gas.endothermic
two types:– Boiling:
• rapid • gas bubbles are produced throughout
– Evaporation• slow • occurs at the surface• is a cooling process• ocean water evaporates to form clouds & rain droplets
CONDENSATIONCONDENSATION
• Change of a gas to a liquid.
• exothermic
• water vapor turns into dew
SUBLIMATION
• Changing directly from solid to gas or gas to solid skipping the liquid state.
• endothermic
• formation of frost/snow & dry ice
FREEZING
• Changing from a liquid to a solid.• Particles lose kinetic energy and slow
down.• exothermic• water turns to ice
CHEMICAL CHANGES
• change of a substance into a new and different substance
• aka chemical reaction
• cannot be reversed by physical changes.
• impossible to “unbake” a cake.
CHEMICAL REACTIONS
Reactants: are the substances that enter a chemical reaction
Products: are the substances formed by a chemical reaction
CHARACTERISTICS & EXAMPLES OF CHEMICAL CHANGES
• Reaction with acids -------Digestion, fizzing• Reaction with oxygen (combustion) -------
Explosions, Burning• Ability to act as oxidizing agent -------- Rusting• Reaction with other elements ----- production of
heat, sound, light• Decomposition into simpler substances ------
change of smell, Decomposing• Corrosion ---- water lines becoming thin• Change in color -----Baking food• Production of a gas ------ Fermentation