Foundations of Chemistry Chapter 7 Physical Science

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.

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= yes Sound= no Light= no

Atom Small particle that is the building block of matter Diameter of hair is 1,000,000x bigger than diameter of an atom Structure of an atom Nucleus (in center of atom) Protons*** Have a positive charge Atomic number= number of protons that determines properties of atom Neutrons Have a neutral charge Electrons (floating around nucleus in electron cloud) Have a negative charge The size of an atom is roughly 10,000x wider than its nucleus.

Substances Matter with a composition that is always the same Substance is always made of the same combination(s) of atoms Examples: oxygen, aluminum, sugar, water Two kinds of substances Elements Compounds

Elements A substance that is made up of only one kind of atom Periodic table of elements About 115 kinds of elements (115 kinds of atoms) Each kind of atom has a different number of PROTONS Aluminum has 13, Oxygen has 8 An Atom with 13 protons is always aluminum. An atom with 8 protons is always oxygen. Substances can exist individually (Al) or in groups (O2)

Compounds A type of substance containing atoms of two or more different elements chemically bonded together. Example: CO2 One atom of carbon and two atoms of oxygen Carbon dioxide is a compound because it is always formed the same way Compounds often have different properties from the individual elements that compose it

Chemical formula The combination of symbols and numbers that represents a compound Show the different atoms in that make up a compound using the element symbols Example: H2O Two hydrogen atoms are bound to one oxygen atom

Mixtures Matter that can vary in composition Combinations of two or more substances that are physically blended together DO NOT combine chemically They can be separated- filtering Two kinds of mixtures heterogeneous homogeneous

Heterogeneous mixtures A mixture in which individual substances are not mixed evenly Two samples of the same mixture can have different concentrations of the substances Examples: two buckets of sand/water taken from the beach

Homogeneous mixture A mixture in which the individual substances are evenly mixed Two samples from a solution will have the same amounts of each substance Also known as a solution Solvent: what is present in the largest amount, what is doing the dissolving Solute: what is present in a smaller amount, what is being dissolved Examples: Apple juice, air or salt water

Compounds vs Solutions Water is a compound so it does not vary Composition is ALWAYS the same H2O is always H2O no matter how much you have H is chemically bound to O Salt water is a solution NaCl (salt) and H2O (water) are mixed together but NOT chemically bound Can add more salt to change relative amounts of salt relative to water= COMPOSITION CAN VARY Can’t use chemical formula to describe

Homework Ch7 L.1 p.237 #1-11 Study for Quiz

Bell work Ch7 L.2 Physical properties: characteristic of matter that you can observe or measure without changing the identify of the matter Mass: the amount of matter in an object Density: mass per unit volume of a substance Solubility: ability of one substance to dissolve in another

Physical properties The arrangement of atoms determines its properties Each element and compound has a unique set of properties How they look, how they react etc.

States of matter ALL atoms that make up matter are constantly moving Solid particles packed close together, not a lot of motion Liquid More motion than a solid. Particles still can touch but they move around relative to one another Gas Most motion of all three states. Particles move very quickly and spread out to fill their container

Size dependent properties Mass: The amount of matter in an object The larger the object the more mass it is Value depends on the size of the object NOT THE SAME AS WEIGHT (weight changes with location but mass does not) Weight depends on gravity Volume: Amount of space something takes up Often measured in mL (milliliters)

Size independent properties Melting point: the point at which a substance changes from solid to liquid Boiling point: the point at which a substance changes from liquid to gas

Size independent properties cont’ Density: mass per unit volume of a substance Conductivity: Electrical- ability to conduct or carry an electrical current Thermal- ability to conduct thermal energy Solubility: ability of one substance to dissolve in another

Separating mixtures Use physical properties things with a lower boiling point will boil off faster CANNOT use physical properties to separate a compound into its elements

Homework Ch7 L.2 p. 246 #1-9 Study for quiz

Bel work Ch7 L.3 Physical change: a change in size, shape, form, or state of matter in which the matter’s identity stays the same

Physical changes Does NOT become something different even though physical properties change Identity stays the same

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

Change in state of matter To change the state, the movement of particles has to change (slower or faster) Adding thermal energy Think of this as adding heat Particles move faster until overcome bonds holding them together The more energy added, the faster the particles move Can change from solid to liquid (melting) to gas (vaporization) Sublimation= change directly from solid to gas

Change in state of matter cont’d Removing thermal energy Think of this as removing heat Particles move slower The more energy removed, the slower the particles move Can change from gas to liquid (condensation) to solid (freezing) Deposition= change directly from gas to solid Freezing/Melting are reverse properties and occur at the same temperature same for boiling/condensation

Dissolving Mixing evenly of substances whose identities do NOT change

Conservation of mass During a physical change even though physical properties can change, the mass does not change

Homework Ch7 L.3 p.253 #1-7 Study for quiz

Bellwork Ch7 L.4 Chemical property: is a characteristic of matter that can be observed as it changes to a different type of matter Chemical change: is a change in matter in which the substances that make up the matter change into other substances with new physical and chemical properties Concentration: is the amount of a substance in a certain volume

Chemical properties Observe only when matter is changing identity (different than physical property)

Signs of chemical changes How do you know if a chemical change has happened? Some hints: bubbles energy change odor change color change These do not automatically mean a chemical change happened, ONLY if a new substance was formed.

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 combinations New substances can form

Chemical formulas Chemical equation: shows the chemical formulas of each substance in a reaction Formulas to the left of the arrow represent the reactants present before the reaction takes place Formulas to the right of the arrow represent the products new substances present after the reaction takes place

Balancing chemical equations Remember that mass is conserved The same number of atoms from each element should be on the left side and right side of the arrow C3H8 + O2 → H2O + 3CO2 Is this balanced? If not, how can we balance it?

Rate of chemical reactions Particles move and collide with each other- the faster this happens the more the rate of a chemical reaction increases.

Rate of chemical reactions cont’d Things that affect rate of chemical reactions Higher temperature= particles move faster Concentration= more particles available to bump into each other Surface area= affects reaction if one reactant is solid. More space for reactants to collide.

Homework Ch7 L.4 p.261 #1-10 Study for quiz Extra credit: Test prep: Outline all of chapter 7 Test prep: p. 265-269