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Chemistry. Chapters 1 and 16. 2 types of chemical rxns :. exothermic- energy is released in the rxn exo - out takes place without help. endothermic- energy is absorbed in rxn endo - in have to have energy in order to occur. Chemistry.

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chemistry

Chemistry

Chapters 1 and 16

2 types of chemical rxns
2 types of chemical rxns:
  • exothermic- energy is released in the rxn
  • exo- out
  • takes place without help
slide3

endothermic- energy is absorbed in rxn

  • endo- in
  • have to have energy in order to occur
chemistry1
Chemistry
  • the study of the composition of substances and the changes they undergo
  • energy is involved in accomplishing these changes
slide6

all of those substances are chemicals

  • chemical- substance that has a definite composition
  • water- H2O
  • sucrose- C12H22O11
  • hematite- Fe2O3
branches of chemistry
Branches of Chemistry
  • 2 major:

1. inorganic- concerns substances that are usually without carbon

2. organic- study of substances containing carbon

subst from living things

types of research
Types of research:

1. basic research- carried out for the sake of increasing knowledge

chance discoveries can occur and have changed our lives!

slide9

2. applied research- carried out to solve problems

depletion of ozone layers by CFCs led scientists to develop new refrigerants

matter
Matter
  • Which of the following could be called matter?
matter1
Matter
  • anything that has a volume and a mass
    • mass- measure of the amount of matter

use a balance to measure

    • volume- amount of space a 3D object takes up
slide13

many forms of matter

  • fundamental building blocks of matter:
    • atoms and molecules

What’s the difference?

slide15

atom- smallest unit of an element that maintains the chemical identity of that element

  • molecule- smallest unit of a diatomic element or a compound that retains all the properties of that subst
  • elements generally make up molecules
slide17

these particles make up elements and compounds

  • What’s the difference?
  • elements- pure subst that CANNOT be broken down into simpler, stable subst; made of 1 kind of atom
slide18

compound- subst that can be broken down into simpler, stable subst

    • usu made from 2 or more kinds of atoms
properties of matter
Properties of Matter
  • used to distinguish between subst and to separate them
  • help to reveal unknown subst
  • ALL matter has many properties by which it can be grouped
  • properties are either intensive or extensive
intensive properties
Intensive Properties
  • do NOT depend on the amount of matter examined
  • same for a 0.5g sample as 500kg sample
  • ex: melting point, boiling point, density, conduction of electricity
extensive properties
Extensive Properties
  • DO depend on the amount of matter present
  • there will be a difference in a 0.5g sample and a 500kg sample
  • ex: volume, mass, amount of energy in sample
slide23

properties can also be grouped into 2 general categories:

1. physical properties- characteristic that can be observed or measured without changing the identity of the substance

ex: color, density, hardness, melting point, boiling point

slide24

2. Chemical properties- prop that matter exhibits as it undergoes changes that transform it into different subst

easiest to see as matter reacts to form new subst

ex: reactivity with oxygen, flammability

matter frequently goes thru changes 2 types of changes
Matter frequently goes thru changes2 types of changes:

1. physical chg- a change in a subst that does NOT involve a chg in the identity of the subst

ex: melting, boiling, grinding, tearing, cutting

slide26

2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst

ex: rusting, tarnishing, burning

slide27

some phy chg are part of an important class of chgs called change of state

    • phy chg of a subst from one state to another
    • 4 main states of matter:
    • STATES OF MATTER FOLDABLE
slide29

2. chemical changes- aka chemical reactions- a chg in which the subst is converted into different subst

ex: rusting, tarnishing, burning

chemical rxn
Chemical Rxn

magnesium plus oxygen yields magnesium oxide

Mg + O2 MgO

parts of chemrxn:

1. reactants- the substances that react in the chemrxn

arrow points AWAY FROM reactants

slide31

2. products- the subst that are formed by the chem chg

arrow ALWAYS POINTS TO products

3. arrow stands for yields

ex: p. 10 fig.7

energy
Energy
  • ALL changes (physical OR chemical) will involve energy
  • can be different forms, like heat and light
  • boundaries between phy and chemchgs are not always very clear
  • in any chg, the total amount of energy involved DOES NOT change
  • the Law of conservation of energy
classification of matter
Classification of Matter
  • tremendous variety of forms of matter
  • can be categorized into 2 groups:

1. pure substance- composition is same thruout

      • can be elements or compounds

2. mixture- contains more than 1 subst; can vary in composition and properties

pure substances
Pure Substances
  • every sample has a fixed composition
    • H2O (by mass, 88.8% O and 11.2% H)
  • every sample has exactly the same characteristic properties
  • properties can be used to identify the subst
  • either elements or compounds
mixtures
Mixtures
  • blend of 2 or more kinds of matter, each retaining its own identity and properties
  • usu physically combined and can be separated
  • properties of mixture are a combination of the properties of subst that make it up
  • 2 types of mixtures:
1 homo geneous mixtures
1. homogeneous mixtures
  • homo- same
  • looks the same thru-out
  • uniform in composition
  • aka- solutions
  • may be solids, liquids, gases
2 parts to a soln
2 parts to a soln:
  • solvent- part that does the dissolving

usu water

aka- the universal solvent

2. solute- part that is dissolved

2 hetero geneous mixture
2. heterogeneous mixture
  • hetero- different
  • may look different
  • composed of more than one phase
  • separated by boundaries called interfaces
elements
Elements
  • substances composed of only one kind of atom
  • ALWAYS have the same composition
  • ex: gold, mercury, hydrogen
compounds
Compounds
  • substances composed of more than one kind of atom always arranged in definite ratios
  • ex: copper II sulfate, CuSO4
  • sucrose, C12H22O11
in chemical changes
In chemical changes:
  • one or more subst are used up
  • 1 or more new subst are formed
  • energy is absorbed or released
evidence of chemical changes
Evidence of chemical changes:
  • color change
  • formation of precipitate (ppt)
slide43

gas bubbling

  • energy changes- heat, light
2 types of chemical rxns1
2 types of chemical rxns:
  • exothermic- energy is released in the rxn
  • exo- out
  • tend to take place without help
slide45

endothermic rxn- energy is absorbed in the rxn

  • endo- inside
  • have to have input of energy to occur
physical changes
Physical Changes
  • occur with NO changes in the composition
  • can be:
    • chgs of state
    • cutting/breaking
    • dissolving
    • distillation
    • fractional crystallization
energy1
Energy
  • phy and chemchgs ( ) always accompanied by energy changes
  • energy changes occur betw sys and surroundings
  • energy transfer as a result of temp difference is HEAT
  • can measure energy chg using units called Joules (J)
slide48

older unit used is calorie

  • 1 cal = 4.184 J
  • food calorie is a larger unit
  • 1 CAL = 1 000 cal
  • convert betw units
thermochemistry
Thermochemistry
  • study of the transfer of heat energy that accompany chemrxns and physical chg
  • temp- is a measure of the average kinetic energy of the particles in a sample of matter
  • greater KE, higher temp, hotter it feels
slide51

K= oC + 273

  • HEAT- measure of the total amount of kinetic energy of the particles in a sample of matter
  • ALWAYS moves from matter at a higher temp to matter at a lower temp
  • fig 1, p.532
specific heat
Specific Heat
  • Will you take a piece of the crust with your finger?
  • Will you stick your finger into the filling of the pie?
  • Why won’t you?
  • Is there a difference?
slide54

some materials tend to heat up and stay hotter longer than other materials

  • dependent on obj’sSPECIFIC HEAT
    • amount of energy required to raise the temp of 1 g of a subst by 1oC (or 1K)
    • Cp
    • units are: J/(goC)
    • Cp H2O= 4.184J/goC
    • table 1, p.533
slide55

use the formula:

q = m x Cp x Temp

heat = mass x specific heat x (Tf-Ti)

when heat is gained, Tf-Ti

when heat is lost, Ti-Tf

slide56

ex: How much heat energy is needed to increase the temp of 755g of Fe from 283oC to 403oC?

How much energy must a refrigerator absorb from 225g of water so that the temp of the water will drop from 35.5oC to 5.0oC?

What mass of water is required to absorb 470 000J of energy from a car engine while the temp increases from 25.0oC to 82.5oC?

Apiece of copper alloy with a mass of 85.0g is heated from 30.0oC to 45.5oC. In the process, it absorbs 523J of heat. What is its specific heat?

slide57

ex: How much heat energy is needed to increase the temp of 755g of Fe from 283oC to 403oC?

How much energy must a refrigerator absorb from 225g of water so that the temp of the water will drop from 35.5oC to 5.0oC?

slide58

What mass of water is required to absorb 470 000J of energy from a car engine while the temp increases from 25.0oC to 82.5oC?

  • Apiece of copper alloy with a mass of 85.0g is heated from 30.0oC to 45.5oC. In the process, it absorbs 523J of heat. What is its specific heat?
slide59

any heat lost by 1 quantity of matter must be gained by the other quantity of matter in a system

  • one will lose heat to the other until both are at the same temp
  • (law of conservation of energy)
  • fig 1, p.532
measuring temp
Measuring Temp
  • If a piece of gold with amass of 45.5g and a temp of 80.5oC is dropped into 192g of water at a temp of 15.0oC, what is the final temp of the system?
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