Chapter 3 Matter Properties and Changes

CHEMISTRY IS THE STUDY OF MATTER AND ITS CHANGES What is matter? Is everything matter? What is the difference between matter and energy? How does matter change?

Properties of Matter Matter is anything that has mass and volume (takes up space). Everything in the room is made of matter…including AIR All Matter is made of atoms. Atoms are the basic building blocks of matter

Categories for types of matter VOCABULARY USED TO CATEGORIZE MATTER ELEMENTS are single atoms or groups of single types of atoms (the element oxygen exists as O2 a group of 2 oxygen atoms) COMPOUNDS are two or more different types of atoms connected or chemically bonded together (water, H2O is a compound that has oxygen and hydrogen connected together) Compounds have UNIQUE properties different from the individual elements themselves MIXTURES are a physical combination of atoms without a connection or chemical bond (steel is a mixture of Fe and C) There are no bonds between the different atoms.

Which one is it…element, compound or mixture Carbon dioxide Air Iron and copper Steel Salad dressing Isopropanol (rubbing alcohol) H2 NaCl S8 N2 and O2 O2

DENSITY is a property of matter Density is a ratio that compares an objects mass to its volume. The unit for density is g/ L or g/ cm3 The units for density are always a mass unit (like grams) divided by a unit of volume ( like liters or mL or cubic cm) A large piece of Styrofoam has the same mass as a quarter, but the quarter has a smaller volume. The quarter has a greater density, because there is a greater amount of mass contained in a smaller space. We can compare the density of two samples to see if the samples are made of the same matter.

A 5-mL sample of water has a mass of 5 g. What is the density of water? An object with a mass of 7.5 g raises the level of water in a graduated cylinder from 25.1 mL to 30.1 mL. What is the density of the object? The density of aluminum is 2.7 g/mL. What is the volume of 8.1 g?

Properties of Matter Properties of matter can be physical or chemical. Physical properties are properties that can be observed or measured without changing the composition of the substance. Physical properties include density, color, odor, hardness, texture, taste, luster (shiny or dull), melting/freezing point (temperature) and boiling point

Extensive and Intensive Physical Properties Extensive properties depend on the amount of the substance present. Length, for example is an observable, extensive physical property. Intensive properties do not depend on the amount of substance. Density, for example is an intensive physical property, because the density of a substance does not change, no matter how much of the substance is present.

Chemical Properties Chemical properties of matter allow a substance to change composition as a result of contact with another substance or because of the application of thermal or electrical energy. If a substance is not reactive with another substance, that is a chemical property also. Examples of chemical properties include the ability to rust, burn, release gas, absorb or give off energy.

States of Matter All matter exists under normal conditions as either a solid, liquid, or gas. Plasma is also a form of matter. In which the atoms begin to break apart into electrons and cations (pronounced cat- ions) Bose-Einstein condensate is a state of matter only found at close to ABSOLUTE zero (This is 0 Kelvin.) It is more dense than a solid. In order from cold to hot or most dense to least dense: Bose-Einstein condensate, solid, liquid, gas, plasma Vapor is NOT the same as a gas!! A vapor is a word used to describe when a substance that is a solid or liquid at room temperature is heated enough to take a gaseous form.

Answer these questions in your notebook. Is ALL paper the same? What is paper made out of? Is there more than one ingredient? Is paper a compound or a mixture? How could you make a physical change to the paper? Do you still have paper after you make the physical change? With 3 other people around you, make 4 DIFFERENT PHYSICAL CHANGES to the papers. List two chemical changes that could be made with the paper.

Particles held tightly together Solid Liquid Gas Definite shape Definite volume Particles held tightly together Particles expand when heated Takes shape of container, but does not have to fill it Particles held close, but not tightly together Takes shape of containers and fills it completely No definite volume Particles are far apart, so it can be compressed

Changes in Matter Physical changes are changes which alter a substance without changing its composition. Examples are breaking glass, tearing paper, melting ice, cutting wood grating or sanding. Changes of state are physical changes. When energy is added to solid water, it changes to liquid water, when more energy is added, it is changed to gaseous water. All the time it is still water. Only a physical change has taken place.

Changes in Matter Melting and boiling points are intensive physical properties. The temperature when boiling occurs does not change when the amount of substance changes. Is the boiling point for one cup of water the same as the boiling point for swimming pool full of water? Intensive physical properties can be used to identify unknown substances.

Chemical Changes Chemical change is defined as one or more substances combining to become one or more new substances. Also known as a chemical reaction Examples of common chemical reactions include burning wood, rusting iron, fermenting of barley and hops to make beer, and explosions.

Chemical Changes Signs that a chemical reaction may have taken place include: Thermal energy (heat) is given off or absorbed Light is produced Precipitate (solid) is formed Color has changed permanently Gas is formed

Chemical Reaction vocabulary REACTANTS are compounds or elements that are combined to make a chemical reaction PRODUCTS are compounds or elements that are created or produced by a chemical reaction CHEMICAL REACTIONS ARE REPRESENTED BY AN ARROW REACTANTS PRODUCTS

The Law of Conservation of Mass states that mass is neither created nor destroyed in any process, it is conserved. Mass of reactants = Mass of products A student carefully placed 15.6 g of sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete, the student obtained 39.7 g of sodium chloride. How many grams of chlorine gas reacted? How many grams of sodium reacted?

Mass of reactants = Mass of products 15.6 g Na + ? g Cl = 39.7g NaCl 24.1g Cl = 39.7g NaCl - 15.6 g Na 24.1 g of chlorine gas is used in the reaction. Because the sodium reacts with excess chlorine, all of the sodium (15.6 g) is used in the reaction.

Law of Conservation of Energy In any chemical reaction or physical process, energy can be converted from one form to another, but it is neither created nor destroyed.

Classify each of the following as examples of physical or chemical changes Crushing an aluminum can Recycling used aluminum cans to make new cans Aluminum combining with oxygen to form aluminum oxide

Mixtures of Matter A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties. The composition of a mixture is variable. Mixtures can be heterogeneous or homogeneous.

Mixtures of Matter A heterogeneous mixture is one in which the substances still remain distinct. Examples include sand/ water, Skittles, fruit salad, vegetable soup. The existence of two or more distinct areas indicate a heterogeneous mixture. Two samples of the mixture could have DIFFERENT compositions

Mixtures of Matter A homogeneous mixture has a consistent composition throughout. It exists in one phase. Examples include salt and water, Kool-Aid, gold jewelry. Homogeneous mixtures are often referred to as solutions. Two samples from a homogeneous mixture have the SAME composition

Mixtures Example Gas-gas Gas-liquid Liquid-gas Liquid-liquid Air is primarily a mixture of nitrogen, oxygen, and argon gasses Gas-liquid Carbonated beverages contain carbon dioxide gas in solution Liquid-gas Moist air contains water droplets in air Liquid-liquid Vinegar contains acetic acid in water Solid-liquid Sweetened powder drink contains sugar and other solid ingredients in water Solid-solid Steel is an allow of iron containing carbon

Separating Mixtures A mixture is a combination of substances physically combined. Physical separation methods take advantage of known physical properties of individual components of a mixture. Filtration uses a solid barrier to separate heterogeneous mixtures of a solid and a liquid (sand & water). Distillation uses differences in boiling points to separate a homogeneous mixture.

Distillation

Separating Mixtures Crystallization separates a mixture and forms a solid that is pure. Like making rock candy.

Chromatography separates components of a mixture on the basis of the tendency of each to travel or be drawn across the surface of another material.

Elements & Compounds Elements are substances that cannot be broken down any further by either chemical or physical methods. Elements are pure substances. Elements have a unique name and chemical symbol. The symbol consists of one, two or three letters. The first letter is always capitalized and any following letters are lowercase.

Elements & Compounds The elements in the periodic table are grouped by patterns in their physical and chemical properties. In 1869, Dmitri Mendeleev organized the elements in rows and columns based on their masses. That was the first version of the periodic table. One of the greatest aspects of Mendeleev’s table was that it left spaces for elements not yet discovered!

Elements The horizontal rows in the periodic table are called periods The vertical columns are called groups or families. The table is called a “periodic” table, because the elements have patterns of similar properties as you move from period to period.

Elements & Compounds Compounds are two or more elements chemically combined. The names of compounds are written by using the element’s symbols. Salt is written NaCl, hydrochloric acid is written HCl. Compounds can be broken down into simpler substances, unlike elements. In order to do that, electrical or heat energy must be added. Compounds do not resemble the elements from which they are made. For example, salt, NaCl, is made from sodium (a silvery metal that burns when exposed to water), and chlorine (a greenish, poisonous gas). However, when these two combine, they form simple table salt that flavors food.

Law of Definite Proportions Regardless of the amount, a compound is always composed of the same elements in the same proportions by mass. Regardless of the amount of water it will always have the same percent by mass of oxygen and hydrogen The ratio of the mass of each element to the total mass of the compound as a percentage is called the percent by mass. Percent by mass % mass = mass of element x 100 mass of compound