Matter and Its Properties 1

Chemistry – the study of the composition, structure, and properties of matter and of the changes that occur in matter Composition – refers to the types of atoms and their relative proportions in a sample of matter 2

Mass – a measure of the amount of matter List some units used for mass: Matter has 2 General Properties Matter – anything that has mass and takes up space Volume – the amount of three- dimensional space an object occupies List some units used for volume: All matter is composed of atoms 3

Mass vs. Weight Mass is a measure of the quantity of matter in an object while….. Weight is defined as the force produced by gravity acting on mass Mass is measured in g or kg (metric) or slugs (English) Weight is measured in newtons (metric) or pounds (English) 4

We can study the properties of matter. They may be physical properties or they may be chemical properties. List some chemical properties of the fireworks: List some physical properties of this substance: 5

Physical Physical Property – a characteristic that can be observed or measured without changing the identity of the substance ( melting point, boiling point, color, odor, density, hardness) List more here: Physical Change – a change in a substance that does not involve a change in the identity of the substance (grinding, cutting, melting, boiling) List more here: 6

Physical Properties Density – It is the amount of mass contained in a specified volume Density can be used to identify substances. For example, you can determine whether an object that appears to be gold is actually gold based on its density. Just determine its mass and its volume and then use the density formula. D= m V The density of gold is 19.3 g/cm 3 Density can be determined without changing the gold chemically so this proves that density is a physical property. So if the density of the unknown is not 19.3 g/cm 3, it’s not gold. 7

Physical Properties of Metals Malleability – can easily be hammered or rolled into sheets Ductility- can easily be drawn into a wire Examples: copper and gold are both malleable and ductile. gold leafcopper wire 8

Phase Changes are Physical Changes SOLIDLIQUIDGAS melting evaporation sublimation Reverse sublimation or deposition freezing condensation 9

Phase Changes: Freezing - changing from a liquid to a solid Melting – changing from a solid to a liquid Condensation – changing from a gas to a liquidEvaporation – changing from a liquid to a gas Sublimation – changing from a solid to a gas Deposition – changing from a gas to a solid 10

Classifying Matter According to its State Solid – definite volume, definite shape Liquid – definite volume, indefinite shape Gas – indefinite volume, indefinite shape 3 Main States: Solid, Liquid, Gas } three main states 11

Chemical Chemical Property – relates to a substance’s ability to undergo changes that transform it into different substances (Ex: charcoal burning in air) Chemical Change – a change in which one or more substances are converted into different substances Reactants – the substances that react in a chemical change Products – the substances that are formed by the chemical change Rusting: chemical change 12

We can observe the physical and chemical properties of the same substance. For example, the physical properties of mercury are: Silver-white, liquid metal In the solid state, mercury is ductile and malleable and can be cut with a knife. The chemical properties of mercury are: Combines readily with sulfur at normal temperatures. Reacts with nitric acid and hot sulfuric acid. Oxidizes to form mercury (II) oxide upon heating in the air. 13

Indications of a Chemical Reaction 1.Color change (unexpected) 2. Formation of a precipitate (solid) 3. Formation of a gas 4. Temperature change increase (heat is given off) = exothermic reaction decrease (heat is absorbed) = endothermic reaction Chemical Reactions - Signs of a Reaction 14

Indications of Chemical Reaction cont’d 5. Light is emitted 6. Change in volume 7. Change in electrical conductivity 8. Change in melting or boiling point 9. Change in smell or taste 10. A change in any distinctive chemical or physical property 15

Matter mixtures elements compounds homogeneous heterogeneous solutions suspensions Pure substances Separated by chemical means Separated by physical means

Classification of Matter Pure Substance – has a fixed composition and differs from a mixture in the following ways: 1.) Every sample of a given pure substance has exactly the same characteristic properties. 2.) Every sample of a given pure substance has exactly the same composition. Pure substances can be classified as either an element or a compound. List some elements here: List some compounds here: 17

Basic Building Blocks Atom – the smallest unit of an element that maintains the chemical identity of that element Element – a pure substance that cannot be broken down into simpler, stable substances It is composed of one type of atom Iron: Element 18

Atom vs. Element All matter is made of atoms. There are 116 different kinds of atoms. An element is made of just one kind of atom. For example, silver is an element and a piece of silver is made of a large number of identical atoms of silver. One speaks of an atom of (the element) silver. A single atom is seldom called an element. Think about the diagram below: 19

Molecules and Compounds Molecule – the physical representation of two or more atoms chemically combined in fixed ratios. d different Compound – a pure substance comprised of two or more different types of atoms chemically bonded in fixed ratios. All compounds are molecules but not all molecules are compounds. 20

Diatomic Elements Diatomic Elements are elements that exist in nature as two atoms of their own kind chemically bonded together. They are classified as elements but… Hydrogen - H 2 Nitrogen - N 2 Oxygen - O 2 Fluorine - F 2 Chlorine - Cl 2 Bromine - Br 2 Iodine - I 2 We call them molecules too!!!! 21

Molecules of a compound can be represented several ways: a molecular formula, a structural formula, a ball-and-stick model, and a space-filling model. For example, the molecular formula of a aspirin is C 9 H 8 O 4 The structural formula for aspirin is The ball and stick model for aspirin is The space filling model for aspirin is 22

SO 2 O 2 Fe C 6 H 12 O 6 Pb(NO 3 ) 2 H 2 Molecule; compound Label the following using atom (A), molecule (M), element (E), compound (C). Molecule; element Atom; element Molecule; compound Molecule; element 23

A compound can be broken down into smaller units (elements). Decomposition by Heat 24

Compounds can be made from elements. 25

Classification of Matter Mixture – a blend of two or more kinds of matter, each of which retains its own identity and properties Types of Mixtures: homogeneous or heterogeneous + Salt Water: Choc. Chip Cookie: 26

Homogeneous mixtures are uniform throughout and do not settle out upon standing undisturbed. Homogeneous Mixture Solutions

This type of homogeneous mixture is composed of two parts. When mix together they are uniform throughout, just one phase Solute: It is the dissolved substance and it is present in smaller quantity Solvent: It is the dissolving substance and it is present in larger quantity + SOLUTESOLVENT Solution They cannot be separated by filtering or centrifuging. Salty water: uniform throughout

A centrifuge is a machine that uses centrifugal force to separate particles of varying density

Solution This is how solutions appear at molecular level. Solute: sugarSolvent: water 30

Heterogeneous mixtures do not have the same composition, properties and appearance throughout. Heterogeneous Mixture Homogeneous mixture Heterogeneous mixture

Muddy Water : An example of heterogeneous mixture (also called a suspension) After some hours

There are mixtures all around us. Can you think of some? Listthem here. Categorize them as homogeneous or heterogeneous. 33

Distinguishing Compounds from Mixtures A compound is composed of two or more elements chemically combined. A mixture is composed of two or more substances physically combined. The properties of a mixture reflect the properties of the substances that it contains. The properties of a compound are often different than the elements that make it up. The composition of a compound remains constant, meaning that sodium chloride is always 39% sodium and 61% chloride. The composition of a mixture may vary depending on how much of each material was combined. + sodiumchlorine sodium chloride View video Salt water is a mixture that has properties of both the salt and the water. 34

Let’s Practice /bhs/teachers/Dana/chemphys.ht ml 35