Presentation on theme: "Foundations of Chemistry"— Presentation transcript:
1 Foundations of Chemistry Chapter 7Physical Science
2 Bell Work Ch7 L.1 Matter: anything that has mass and takes up space. Atom: a small particle that is a building block of matter.Substance: matter with a composition that is always the same.Element: a substance that consists of just one type of atom.Compound: a type of a substance containing atoms of two or more different elements chemically bonded together.Mixture: matter that can vary in composition.Heterogenous mixture: a type of mixture in which the individual substances are not evenly mixed.Homogeneous mixture:a type of mixture in which individual substances are evenly mixed.Dissolve: to form a solution by mixing evenly.
3 Matter Look around- what makes up objects around you? Things can be made up of different kinds of matter.What about things you can’t see?Air?Does it have mass? Does it take up space?IF YES TO BOTH= matter.Air= yesSound= noLight= no
4 Atom Small particle that is the building block of matter Diameter of hair is 1,000,000x bigger than diameter of an atomStructure of an atomNucleus (in center of atom)Protons***Have a positive chargeAtomic number= number of protons that determines properties of atomNeutronsHave a neutral chargeElectrons (floating around nucleus in electron cloud)Have a negative chargeThe size of an atom is roughly 10,000x wider than its nucleus.
5 Substances Matter with a composition that is always the same Substance is always made of the same combination(s) of atomsExamples: oxygen, aluminum, sugar, waterTwo kinds of substancesElementsCompounds
6 Elements A substance that is made up of only one kind of atom Periodic table of elementsAbout 115 kinds of elements (115 kinds of atoms)Each kind of atom has a different number of PROTONSAluminum has 13, Oxygen has 8An Atom with 13 protons is always aluminum. An atom with 8 protons is always oxygen.Substances can exist individually (Al) or in groups (O2)
7 CompoundsA type of substance containing atoms of two or more different elements chemically bonded together.Example: CO2One atom of carbon and two atoms of oxygenCarbon dioxide is a compound because it is always formed the same wayCompounds often have different properties from the individual elements that compose it
8 Chemical formulaThe combination of symbols and numbers that represents a compoundShow the different atoms in that make up a compound using the element symbolsExample: H2OTwo hydrogen atoms are bound to one oxygen atom
9 Mixtures Matter that can vary in composition Combinations of two or more substances that are physically blended togetherDO NOT combine chemicallyThey can be separated- filteringTwo kinds of mixturesheterogeneoushomogeneous
10 Heterogeneous mixtures A mixture in which individual substances are not mixed evenlyTwo samples of the same mixture can have different concentrations of the substancesExamples: two buckets of sand/water taken from the beach
11 Homogeneous mixtureA mixture in which the individual substances are evenly mixedTwo samples from a solution will have the same amounts of each substanceAlso known as a solutionSolvent: what is present in the largest amount, what is doing the dissolvingSolute: what is present in a smaller amount, what is being dissolvedExamples: Apple juice, air or salt water
12 Compounds vs Solutions Water is a compound so it does not varyComposition is ALWAYS the sameH2O is always H2O no matter how much you haveH is chemically bound to OSalt water is a solutionNaCl (salt) and H2O (water) are mixed together but NOT chemically boundCan add more salt to change relative amounts of salt relative to water= COMPOSITION CAN VARYCan’t use chemical formula to describe
14 Bell work Ch7 L.2Physical properties: characteristic of matter that you can observe or measure without changing the identify of the matterMass: the amount of matter in an objectDensity: mass per unit volume of a substanceSolubility: ability of one substance to dissolve in another
15 Physical properties The arrangement of atoms determines its properties Each element and compound has a unique set of propertiesHow they look, how they react etc.
16 States of matter ALL atoms that make up matter are constantly moving Solidparticles packed close together, not a lot of motionLiquidMore motion than a solid. Particles still can touch but they move around relative to one anotherGasMost motion of all three states. Particles move very quickly and spread out to fill their container
17 Size dependent properties Mass: The amount of matter in an objectThe larger the object the more mass it isValue depends on the size of the objectNOT THE SAME AS WEIGHT (weight changes with location but mass does not)Weight depends on gravityVolume: Amount of space something takes upOften measured in mL (milliliters)
18 Size independent properties Melting point: the point at which a substance changes from solid to liquidBoiling point: the point at which a substance changes from liquid to gas
19 Size independent properties cont’ Density: mass per unit volume of a substanceConductivity:Electrical- ability to conduct or carry an electrical currentThermal- ability to conduct thermal energySolubility: ability of one substance to dissolve in another
20 Separating mixtures Use physical properties things with a lower boiling point will boil off fasterCANNOT use physical properties to separate a compound into its elements
22 Bel work Ch7 L.3Physical change: a change in size, shape, form, or state of matter in which the matter’s identity stays the same
23 Physical changesDoes NOT become something different even though physical properties changeIdentity stays the same
24 Change in shape and size Can break things into smaller pieces or fold things into different shapes but doesn’t change the identity of the material
25 Change in state of matter To change the state, the movement of particles has to change (slower or faster)Adding thermal energyThink of this as adding heatParticles move faster until overcome bonds holding them togetherThe more energy added, the faster the particles moveCan change from solid to liquid (melting) to gas (vaporization)Sublimation= change directly from solid to gas
26 Change in state of matter cont’d Removing thermal energyThink of this as removing heatParticles move slowerThe more energy removed, the slower the particles moveCan change from gas to liquid (condensation) to solid (freezing)Deposition= change directly from gas to solidFreezing/Melting are reverse properties and occur at the same temperaturesame for boiling/condensation
27 DissolvingMixing evenly of substances whose identities do NOT change
28 Conservation of massDuring a physical change even though physical properties can change, the mass does not change
30 Bellwork Ch7 L.4Chemical property: is a characteristic of matter that can be observed as it changes to a different type of matterChemical change: is a change in matter in which the substances that make up the matter change into other substances with new physical and chemical propertiesConcentration: is the amount of a substance in a certain volume
31 Chemical propertiesObserve only when matter is changing identity (different than physical property)
32 Signs of chemical changes How do you know if a chemical change has happened? Some hints:bubblesenergy changeodor changecolor changeThese do not automatically mean a chemical change happened, ONLY if a new substance was formed.
33 Chemical reactions Particles can move and collide with one another If they hit each other with enough force they can break apart and then can form new bonds and new combinationsNew substances can form
34 Chemical formulasChemical equation: shows the chemical formulas of each substance in a reactionFormulas to the left of the arrow represent the reactantspresent before the reaction takes placeFormulas to the right of the arrow represent the productsnew substances present after the reaction takes place
35 Balancing chemical equations Remember that mass is conservedThe same number of atoms from each element should be on the left side and right side of the arrowC3H8 + O2 → H2O + 3CO2Is this balanced?If not, how can we balance it?
36 Rate of chemical reactions Particles move and collide with each other- the faster this happens the more the rate of a chemical reaction increases.
37 Rate of chemical reactions cont’d Things that affect rate of chemical reactionsHigher temperature= particles move fasterConcentration= more particles available to bump into each otherSurface area= affects reaction if one reactant is solid. More space for reactants to collide.
38 Homework Ch7 L.4 p.261 #1-10 Study for quiz Extra credit: Test prep: Outline all of chapter 7Test prep:p