Chapter 2 Matter and Change

What is Matter? Matter is anything that takes up space and has mass. Mass is the amount of matter in an object

Types of Matter Pure Substance- a particular kind of matter – pure - Elements - Compounds Mixture- more than one kind of matter, not chemically combined

What are Pure Substances? Substances which have a single composition throughout. These can be elements or compounds

Pure copper Sugar Tea (water, oil) (Cu) (C6H12O6) (Sugar, Water, tea)

Elements: Simplest form of matter Atoms: Smallest part of an element Periodic Table of Elements

Examples of Elements: Anything on here! Oxygen Gold Sodium Copper Calcium Silver Carbon Potassium Aluminum

Pure Substances Cont. Compounds: Two or more elements chemically combined Molecule: Smallest part of a compound A happy water molecule (H2O)

Sugar: a compound that has these three things chemically combined… 1. Carbon 2. Hydrogen 3. Oxygen A Sugar Molecule (C6H12O6 )

More examples of compounds: Salt (NaCl) Sodium Chlorine 2. Water (H2O) a. Hydrogen (2 atoms) b. Oxygen 3. Baking Soda (NaHCO3) a. Sodium b. Hydrogen c. Carbon d. Oxygen (3 atoms)

Lets Look at Salt (NaCl) Salt is a compound: meaning it has two or more elements chemically combined These two elements by themselves are VERY different The two elements? Sodium (Na) Chlorine (Cl)

Sodium (Na) Incredibly reactive, will explode in water (And yes, we are throwing this in water one day) Is a soft metal (you can cut it with a blunt knife)

Chlorine (Cl) A toxic, green gas Used to clean swimming pools (when combined with other stuff) The reason we almost didn’t have school that one day Poisonous! Dangerous!

Wait… So if we combine an element that EXPLODES IN WATER with… An element that COULD KILL US… We get…

The Compound Salt!!! (NaCl) The stuff we eat EVERY day…

Pause for a visual… https://www.youtube.com/watch?v=n2qbtvpedMU = https://www.youtube.com/watch?v=WVonuBjCrNo

A molecule is the smallest particle of a compound that acts as a unit A molecule is the smallest particle of a compound that acts as a unit. Water molecule. Molecules are made of a fixed ratio of atoms.

What is a chemical formula? A chemical formula tells the kind and number of atoms in a molecule. The formula uses the symbols of the element to identify the elements present and subscripts (lowered numbers beside the symbol) to indicate how many atoms are present.

Mixtures

Compound or Mixture Compound Mixture One kind of piece- Molecules More than one kind - Molecule or atoms Making is a chemical change Making is a physical change Only one kind Variable composition

Which is it? Compound Mixture Element

Properties Words that describe matter (adjectives) Physical Properties- a property that can be observed and measured without changing the substance. Chemical Properties- a property that can only be observed by changing the type of substance. Both physical and chemical properties can be used to help identify a substance

Physical Properties Color Melting Boiling

Chemical Properties Flammability Radioactivity Reactivity

Properties Words that describe matter (adjectives) Extensive Properties- only depends on the amount of matter Intensive Properties- only depends on the type of matter, not the amount Both intensive and extensive properties can be used to help identify a substance

Extensive Properties Volume Mass

Intensive Properties Density Luster Color

States of matter Solid- matter that can not flow and has definite volume. Liquid- definite volume but takes the shape of its container (flows). Gas- a substance without definite volume or shape and can flow Plasma high temperature low pressure electrons separate from nucleus Most common in the universe

States of Matter Definite Volume? Definite Shape? Temp. increase Com-pressible? Small Expans. Solid YES YES NO Small Expans. Liquid NO NO YES Large Expans. Gas NO NO YES

States of Matter Moderate Kinetic Energy - molecules move around more than in solids Low Kinetic Energy - molecules barely move High Kinetic Energy – molecules in rapid, constant motion

Condense Freeze Melt Evaporate Solid Liquid Gas

Another Way to Change States Pressure For some substances it will turn solids to liquids For others it will turn liquids to solids Silly putty Will turn gas to liquid- Compressor in refrigerator and AC

Physical Changes A change that changes appearances, without changing the composition. Examples? Chemical changes - a change where a new form of matter is formed. Also called chemical reaction. Not phase changes Ice is still water.

Mixtures Made up of two substances. Variable composition. Heterogeneous- mixture is not the same from place to place. Chocolate chip cookie, gravel, soil. Homogeneous- same composition throughout. Kool-aid, air. Every part keeps its properties.

What are homogeneous mixtures? Solutions are homogeneous mixtures. Solution particles are very small and compose molecules, atoms, or ions. Colloids are homogeneous mixtures. Colloid particles are larger than solution particles but do not settle as suspension do. Examples of colloids are fog, mayonnaise, jello, whipped cream. What is the Tyndall Effect and Brownian motion?

What are heterogeneous mixtures? Heterogeneous mixtures (suspensions) are made of larger particles than that of homogeneous mixtures. These particles remain suspended temporarily and will eventually settle or separate. Examples are chocolate milk, orange juice, muddy water.

What are liquid mixtures? Liquids which evenly mix are said to be miscible. Gasoline, antifreeze and water. Liquids which do not mix are said to be immiscible. Oil and water; oil and vinegar. Can gases mix with liquids? How do fish breathe? What are carbonated soft drinks?

Phases A part of a sample with uniform composition, therefore uniform properties Homogeneous- 1 phase Heterogeneous – more than 1

Separating mixtures Only a physical change- no new matter Filtration- separate solids from liquids with a barrier Distillation- separate because of different boiling points Heat mixture Catch vapor in cooled area Chromatography- different substances are attracted to paper or gel, so move at different speeds

Chromatography

How can physical changes be used to separate mixtures? Impurities mixed with water can be separated by distillation. What is distillation? Distillation is a process of separating parts of a mixture by differences in boiling points.

Solutions Homogeneous mixture Mixed molecule by molecule Can occur between any state of matter. Solid in liquid- Kool-aid Liquid in liquid- antifreeze Gas in gas- air Solid in solid - brass Liquid in gas- water vapor

Solutions Like all mixtures, they keep the properties of the components. Can be separated by physical means Not easily separated- can be separated without creating anything new.

Chemical Reactions Another name for chemical change When one or more substances are changed into new substances. Reactants- stuff you start with Products- What you make NEW PROPERTIES Because each substance has its own properties

Indications of a chemical reaction Energy absorbed or released Color change Odor change Precipitate- solid that separates from solution Not easily reversed Only clues not certainty

Chemical symbols There are 116 elements Each has a 1 or two letter symbol First letter always capitalized second never Some from Latin or other languages

Chemical symbols Used to write chemical formulas Subscripts tell us how many of each atom H2O C3H8 HBrO3

Conservation of Mass Mass can not be created or destroyed in ordinary (not nuclear) changes. All the mass can be accounted for. Mass at the start = mass at end

The Law of Conservation of Mass Matter cannot be created nor destroyed.

Energy The ability to do work. Work - cause a change or move an object. Many types- all can be changed into the other.

Types of energy Potential- stored energy Kinetic Energy- energy something has because its moving Heat- the energy that moves because of a temperature difference. Chemical energy- energy released or absorbed in a chemical change. Electrical energy - energy of moving charges

Types of Energy Radiant Energy- energy that can travel through empty space (light, UV, infrared, radio) Nuclear Energy – Energy from changing the nucleus of atoms All types of energy can be converted into others. If you trace the source far enough back, you will end up at nuclear energy.

Conservation of Energy Energy can be neither created or destroyed in ordinary changes (not nuclear), it can only change form. Its not just a good idea, its the law.

What about nuclear? E = mc2 energy = mass x (speed of light)2 speed of light = 3 x 108 A little mass can make a lot of energy Law of Conservation of Mass - Energy the total of the mass and energy remains the same in any change