Chapter 2: Matter & Change

Matter Anything that has mass & take up space Mass = measurement of the amount of matter an object contains Chemistry = the study of matter & the changes that it undergoes

Classifying Matter  Quantitative – numerical information how much, how little, how big, how small  Qualitative – descriptive information condition, color, size, shape, odor, texture

Properties of Matter 1. Extensive – a property that depends on the amount of matter in a sample ex. mass, volume, amount of energy 2. Intensive – a property that depends on the type of matter in a sample ex. hardness, density, boiling point, electrical conductivity Substance – matter that has uniform & unchanging composition has identical intensive properties… Why? because every sample has the same composition

3. Physical Properties – a characteristic that can be observed or measured w/out changing the identity of a substance ex. color, odor, taste, hardness, density,melting/boiling points, state of matter States of Matter – the physical forms in which all matter exists on Earth

Can you identify these 3 states? Solid  def. shape & volume  shape independent of container  particles are packed together Liquid  def. volume  shape depends on container  particles can move freely Gas  indefinite volume & shape  particles move quickly & spread apart

Physical Changes – a change that occurs in the physical appearance of a substance, but does not change its identity breaking, splitting, grinding, cutting, crushing Ex. melting, boiling, freezing, evaporating, dissolving, condensing

4. Chemical Properties – relates to a substances ability to undergo changes that transform it into a different substance  easiest to see when a chemical is reacting Chemical changes – a change that produces matter with a different composition than the original matter ex. burning, rotting, rusting, reacting, cooking, digestion, respiration

Mixtures A combination of 2 or more types of matter Each component keeps its own identity & properties Components are only physically mixed & can be separated using physical means Chicken noodle soup Cinnamon & Sugar Air

Types of Mixtures 1. Heterogeneous mixture - a mixture in which the substances are not evenly distributed Salad Ice tea with ice Oil & vinegar

2. Homogeneous mixture – a mixture or ‘solution’ in which the substances are evenly distributed Kool-Aid Water Stainless Steel

Phase – used to describe any part of a sample with uniform composition & properties Homogeneous mixture 1 phase Heterogeneous mixture 2 phases

1. Filtration – a technique that uses a porous barrier to separate a solid from a liquid Can you think of any common applications? Separating Mixtures  ‘Plays’ on differences in physical properties

2. Distillation – a technique that can be used to physically separate most homogeneous mixtures based on differences in the boiling points of the substances involved

3. Chromatography – a technique that is used to physically separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material

Pure Substances Every sample has same:  characteristic properties  composition Are made of:  one type of atom: element Ex: iron, gold, oxygen  2 or more types of atoms: compound Ex: salt, sugar, water

Which are pure substances?

Element Simplest form of matter that has its own unique set of properties Can not be separated into simpler substances by physical or chemical means Each element is made up of a single type of atom ex. hydrogen, nitrogen, lead

Compound A substance that contains 2 or more elements chemically combined in a fixed proportion Properties are different than the individual elements ex. Glucose (sugar) Glucose – sweet, white solid Carbon – black, tasteless solid Oxygen – colorless, tasteless gas Hydrogen – colorless, tasteless gas

Breaking Down Compounds Physical methods do not work  Recall… Chemical changes – a change that produces matter with a different composition than the original matter

Substances vs. Mixtures

Symbols & Formulas Chemical Symbol each element is represented by a one- or two-letter symbol Trends: 1 st letter = always capitalized 2 nd letter = always lowercase Subscripts = indicate the relative proportions of the elements in a compound H K Au H2OH2O C 6 H 12 O 6 Hydrogen Potassium GoldWaterGlucose

Chemical Reactions The process by which the atoms of one or more substances are rearranged to form different substances Occurrence can be indicated by changes in temperature, color, odor, & physical state Also known as a chemical change Chemical properties can only be observed when a substance undergoes a chemical change

The process of photosynthesis is a chemical reaction in which light energy, carbon dioxide and water, are transformed to create glucose and oxygen.

The photosynthetic chemical reaction can be shown by writing out the element symbols for each compound. Reactants  substances to the left of the arrow  ‘ingredients’  CO 2 and H 2 O Products  substances to the right of the arrow  ‘what is made’ or produced  C 6 H 12 O 6 and O 2

Recognizing Chemical Changes 1. Transfer of energy Energy may be given off in the form of heat or light 2. Change in color Substances may ‘brown’ Indicators  How can you tell whether a chemical change has taken place?

3. Precipitate A solid that settles out of a liquid mixture 4. Gas production Indicated by the formation of ‘gas bubbles’

Conservation of Matter During any chemical reaction, the mass of the products is always equal to the mass of the reactants + O 2 + CO 2 + H 2 O vapor

Conservation of mass also applies to physical changes… 10g of ice 10g of liquid H 2 O

Law of Conservation of Mass In any physical or chemical change, mass is conserved i.e. Mass is neither created or destroyed