2.1 Notes I. Matter Matter—all material you can hold or touch; anything that has mass and takes up space --Every sample of matter is either an element, a compound, or a mixture. Atoms: smallest particle that has properties of an element

Element: -cannot be broken down into similar substances -each element is made of only one kind of atom -each element has a symbol (Al, B) -elements combine chemically to make compounds

4. Compounds are different from the elements that make them

-NaCl, sodium chloride

4. Compounds are different from the elements that make them -NaCl, sodium chloride -sodium is highly combustible

4. Compounds are different from the elements that make them -NaCl, sodium chloride -sodium is highly combustible -chlorine is deadly

4. Compounds are different from the elements that make them -NaCl, sodium chloride -sodium is highly combustible -chlorine is deadly -when the two combine chemically, they form a substance that we eat every day -Each molecule of a compound contains two or more elements that are chemically combined.

5. Molecule: smallest unit of a substance that exhibits properties of the substance -made of atoms -act as a unit -may be made of the same element F 2, Br 2, O 2, N 2, S 8

6. Chemical formulas represent compounds. -Subscript tells how many atoms of each element are in the compound -Numbers in front show # of molecules

H 2 O 1 molecule of water 2 atoms of hydrogen 1 atom of oxygen

3C 12 H 22 O 11 3 molecules of sugar 12 carbon atoms 22 hydrogen atoms 11 oxygen atoms

II. Pure Substance / Mixture Pure substance: matter that has a fixed composition and definite properties ex:

II. Pure Substance / Mixture Pure substance: matter that has a fixed composition and definite properties ex: pure grape juice Mixture: combination of pure substances that are not chemically combined. ex: *Elements and compounds are pure substances, but mixtures are not.

Mixtures 1. Heterogeneous: not uniformly mixed ex

Mixtures 1. Heterogeneous: not uniformly mixed ex 2. Homogeneous: uniformly mixed ex

3. Miscible: liquids that dissolve into each other ex

3. Miscible: liquids that dissolve into each other ex 4. Immiscible: liquids that do not dissolve into each other ex

5. Gases can mix with liquids -carbonated drinks are homogeneous mixtures of liquid and carbon dioxide, CO 2

Make a graphic organizer with these words: Compound Element Heterogeneous Homogeneous Matter Mixture Pure Substance

compound, element, heterogeneous, homogeneous, matter, mixture, pure substance

 Properties of Matter › Pg

 Physical properties are characteristics that can be observed without changing the identity of the substance. › Ex. Shape and mass › Ex. Color, volume, texture

 At room temperature and under atmospheric pressure, all samples of pure water are colorless and liquid.

 Use senses to observe some basic physical properties.  You can observe the state of a substance, the physical form of a substance. › Solid, liquid, and gas

 The temperature at which a substance changes from a solid to a liquid is the melting point.  The temperature at which a liquid changes to a gas is the boiling point.  A characteristic of any pure substance is that its boiling point and its melting point are constant if the pressure remains the same. › At constant pressure, pure water always has the same boiling point and the same melting point.

 Other physical properties that can be measured are: › Strength › Hardness › magnetism › Conducts heat › Conducts Electricity

 Clean or dirty  If something will fit into another thing or not  Clothing matches  Etc.

 Density is a measurement of how much matter is contained in a certain volume of a substance.  Density = mass/volume  D = m/v  Density of a solid is expressed in g/cubic cm  Density of a liquid: g/mL

Find the density of an object that has a mass of 10.0 grams and a volume of 2.5 cubic centimeters. D= m/v

 Read pg. 55

 A chemical property describes how a substance changes into a new substance, either by combining with other elements or by breaking apart into new substances.  Chemical properties are generally not as easy to observe as physical properties.

 Flammability is the ability to burn. › A chemical property of wood is flammability A substance always has its chemical properties, even when you cannot observe them. A substance that does not burn has a chemical property of nonflammability.

Another chemical property is the reactivity of elements or compounds with oxygen, water, or other substances. Reactivity is the capacity of a substance to combine with another substance. Ex. When iron is exposed to oxygen, it rusts.

 You can observe physical properties without changing the identity of the substance.  You can observe chemical properties only in situations in which the identity of the substance changes.  Many substances have either chemical or physical properties in common. › Usually NOT both!

 Changes of Matter › Pg

 A physical change affects one or more physical properties of a substance without changing the identity of the substance. › Ex. Breaking chalk, dissolving sugar in water, sanding a piece of wood, mixing oil and vinegar, cutting, crushing, melting, etc.

 During a physical change, energy is absorbed or released.  After a physical change, a substance may look different, but the arrangement of atoms that make up the substance is not changed.

 When you stir sugar into water, the sugar dissolves and seems to disappear.  Look at Figure 3 on page 60.  When sugar dissolves, the sugar molecules become spread out between the water molecules.  The molecules of the sugar do not change. › Therefore, dissolving is a physical change.

 Some materials are useful because of their ability to change and combine to form new substances.  The burning of the compounds is a chemical change.  A chemical change happens when one or more substances are changed into entirely new substances that have different properties.  The chemical properties of a substance describe which chemical changes can happen.

 Look on pg. 61 at Figure 4  When a battery dies, the chemicals inside the battery have changed.  The oxygen you breathe is undergoing a series of chemical changes and reactions.  Leaves changing colors.  Etc.

 When you mix ingredients together when baking, the interaction of the ingredients together is much different than it would be if each of the ingredients were by themselves.

 A change in odor or color is often a clue that a chemical change has occurred.  Chemical changes often cause color changes, fizzing or foaming, or the production of sound, heat, light, or odor.

 Because new substances are formed in a chemical change, a chemical change cannot be reversed by physical changes.  Most are impossible to reverse. › Under the right conditions, some chemical changes can be reversed by other chemical changes.

 A mixture is a combination of substances that are not chemically combined.  A compound is made up of atoms that are chemically combined.  As a result of this difference, mixtures and compounds must be separated in different ways.  Mixtures can be separated by physical changes, but compounds must be broken down by chemical changes.

 Because mixtures are not chemically combined, each part of a mixture has the same chemical makeup that it had before the mixture was formed.  Each substance keeps its identity.  Therefore, mixtures can be separated by physical means.

 If components of a mixture have different boiling points, you can heat the mixture in a distillation device.  Another technique for separating mixtures is to use a centrifuge.

 Some compounds can be broken down into elements through chemical changes.  Electric currents can be used to separate some compounds.  Other compounds undergo chemical changes to form simpler compounds.