Physical Science Chapter 15 The Classification of Matter 1

15.1 Composition of Matter The Big Idea: Matter can be classified by what it is made of, by its physical properties, and by its chemical properties.

Matter is anything that has mass and takes up space

15. The Classification of Matter Composition of Matter: Matter can be either a pure substance (an element or a compound) mixture (either heterogeneous or homogeneous.) 3

15:1 The Composition of Matter Substance are either elements or compounds. 1. When all the atoms in a substance are alike, the substance is an element. ex: Gold (Au) or Oxygen (O) 4

15:1 The Composition of Matter 2. A compound is a substance with two or more elements combined in a fixed proportion. 5

15:1 The Composition of Matter Elements All substances are built from atoms. If all the atoms in a substance have the same identity, that substance is an element. The graphite in your pencil point and the copper coating of a penny are examples of elements. 3

15:1 The Composition of Matter Elements About 90 elements are found on earth. More that 20 others have been made in laboratories, but most of these are unstable and exist only for short periods of time. 7

15:1 The Composition of Matter Compounds Can you imagine yourself putting something made from a silvery metal and a greenish-yellow, poisonous gas on your food? 8

The Composition of Matter Compounds can not be broken down by physical means must be chemical means

15:1 The Composition of Matter Compounds Table salt is a chemical compound that fits this description. Even though it looks like white crystals and adds flavor to food, its components—sodium and chlorine—are neither white nor salty. 9

15:1 The Composition of Matter Mixture Two or more substances that can be easily separated by physical means form a mixture such as the pizza or soft drink shown. 10

15:1 The Composition of Matter Heterogeneous Mixtures Each substance keeps its own properties (each can be seen) Can be separated by physical means (with your hands) Can have 1 or more states of matter (solid, liquid, gas) 11

Heterogeneous Mixtures Examples Bag of M&M’s Jar of sand Granite Chocolate chip cookie

15:1 The Composition of Matter Most of the substances you come in contact with every day are heterogeneous mixtures. Some components are easy to see, like the ingredients in pizza, but others are not. For example, the cheese in pizza is also a mixture, but you cannot see the individual components. 12

15:1 The Composition of Matter Homogeneous Mixtures Each substance loses its own properties and takes on new properties. Looks the SAME throughout Can only have 1 phase (state of matter) at a time Ex: salt, milk, air, soda 14

15:1 The Composition of Matter Homogeneous Compounds Soft drinks contain water, sugar, flavoring, coloring, and carbon dioxide gas. Soft drinks in sealed bottles are examples of homogeneous mixtures. 13

15:1 The Composition of Matter Another name for homogeneous mixtures like a cold soft drink is solution. A solution is a homogeneous mixture of particles so small they cannot be seen without a microscope and will never settle to the bottom of the container. 15

15:1 The Composition of Matter Solutions remain constantly and uniformly mixed. 16

15:1 The Composition of Matter Colloids Milk is an example of a specific kind of mixture called a colloid. 4. A colloid is a type of heterogeneous mixture with particles that are larger than those in solutions but not heavy enough to settle out. 17

Colloid Examples Jello Ice cream Paint Fog/Smoke shampoo

15:1 The Composition of Matter Detecting Colloids One way to distinguish a colloid from a solution is by its appearance. Fog appears white because its particles are large enough to scatter light. Sometimes it is not so obvious that a liquid is a colloid. You can tell for certain if a liquid is a colloid by passing a beam of light through it. 18

Detecting Colloids A light beam is invisible as it passes through a solution, but can be seen readily as it passes through a colloid. This occurs because the particles in the colloid are large enough to scatter light, but those in the solution are not. A solution does not scatter light. The scattering of light by colloidal particles is called the Tyndall effect.

15:1 The Composition of Matter 4. Suspensions—a heterogeneous mixture containing a liquid in which visible particles settle. Some mixtures are neither solutions nor colloids. One example is muddy pond water. Pond water is a suspension, which is a heterogeneous mixture containing a liquid in which visible particles settle. 20 e

15.2 Properties of Matter The Big Idea: A physical property can be observed without changing the identity of the material. A chemical property describes whether it can undergo a chemical change. 27

15.2 15.2 Properties of Matter A. Physical Property—characteristic of a material which can be observed without changing the identity of the substance in material. Examples of physical properties are color, shape, size, density, melting point, and boiling point. 28

Appearance physical description of a substance 15:2 Physical Properties Appearance physical description of a substance How would you describe a tennis ball? You could begin by describing its shape, color, and state of matter. You can measure some physical properties, too. For instance, you could measure the diameter of the ball. 29

Behavior: how a substance acts 15:2 Physical Properties Behavior: how a substance acts Some physical properties describe the behavior of a material or a substance. Attraction to a magnet is a physical property of the substance iron. Every substance has a specific combination of physical properties that make it useful for certain tasks. 30

1. Appearance –physical description of a substance 15:2 Physical Properties 1. Appearance –physical description of a substance 2. Behavior—how a substance acts; for example, magnetism, viscosity, ductility 3. Physical properties such as size and magnetism can be used to separate mixtures. 31

Using Physical Properties to Separate Look at the mixture of iron filings and sand shown. You probably won’t be able to sift out the iron filings because they are similar in size to the sand particles. What you can do is pass a magnet through the mixture. 32

15:2 Physical Properties B. Physical Change—change in a substance’s size, shape or state of matter. 1. Substance does not change identity when it undergoes a physical change. 34

The Identity Remains the Same 15:2 Physical Properties The Identity Remains the Same Iron is a substance that can change states if it absorbs or releases enough energy—at high temperatures, it melts. Color changes can accompany a physical change, too. 35

The Identity Remains the Same 15:2 Physical Properties The Identity Remains the Same For example, when iron is heated it first glows red. Then, if it is heated to a higher temperature, it turns white. 36

15:2 Physical Properties 2. Distillation is a process for separating a mixture by evaporating a liquid and condensing its vapor. 37

15:2 Physical Properties Distillation The process for separating substances in a mixture by evaporating a liquid and recondensing its vapor is distillation. It usually is done in the laboratory using an apparatus similar to that shown. 38

Examples of Physical Changes crumpling a sheet of paper melting an ice cube casting silver in a mold breaking a bottle

15:2 Chemical Properties and Changes A chemical property a property used to characterize materials in reactions that change their identity. The tendency of a substance to burn, or its flammability, is an example of a chemical property because burning produces new substances during a chemical change. 39

15:2 Chemical Properties and Changes D. When one substance changes to another substance, a chemical change has occurred. 40

15:2 Chemical Properties and Changes The Identity Changes Clues such as heat, cooling, or the formation of bubbles or solids in a liquid are helpful indicators that a reaction is taking place. However, the only sure proof is that a new substance is produced. The only clue that iron has changed into a new substance is the presence of rust. 41

15:2 Chemical Properties and Changes 1. Some chemical changes are indicated by temperature change, smell, or bubble formation. Tarnish is a chemical reaction between silver metal and sulfur compounds in the air which results in silver sulfide. It can be changed back into silver using a chemical reaction. 42

15:2 Chemical Properties and Changes 2. Other chemical changes occur very slowly such as the formation of rust. 43

When the composition of the substance changes Chemical Change When the composition of the substance changes

Chemical Change How to know a chemical change has occurred: Color changes Absorbing or releasing energy Produces an Odor Precipitate (formation of solid) Production of Gas Burning

Chemical Change Examples: Rusting of nail Mold on food Bleaching Fireworks exploding Burning toast Leaves changing color

The Conservation of Mass 15:2 The Conservation of Mass Suppose you burn a large log until nothing is left but a small pile of ashes. At first, you might think that matter was lost during this change because the pile of ashes looks much smaller than the log did. 46

In fact, the mass of the ashes is less than that of the log. The Conservation of Mass In fact, the mass of the ashes is less than that of the log. 47

The Conservation of Mass However, suppose that you could collect all the oxygen in the air that was combined with the log during the burning and all the smoke and gases that escaped from the burning log and measure their masses, too. Then you would find that no mass was lost after all. 48

The law of conservation of mass matter can neither be created or destroyed. 52

The Conservation of Mass Not only is no mass lost during burning, mass is not gained or lost during any chemical change. F. According to the law of conservation of mass, the mass of all substances that are present before a chemical change equals the mass of all the substances that remain after the change. 49

Mass of reactants = mass of products 15:2 Math Skills Mass of reactants = mass of products 50