Chapter 9 Classification of Matter

Element Quizzes and Test Schedule Quiz #1 – Dec. 1st Quiz #2 – Dec. 3rd Quiz #3 – Dec. 8th Quiz #4 – Dec. 10th Quiz #5 – Dec. 15th TEST ON ALL 75 – TBA

9-1 Composition of Matter Elements - a pure substance; matter in which all the atoms are alike. Examples: Carbon – pencil lead ( graphite ); diamonds; coal Copper – pennies ( solid before 1982 ), pipes Chlorine – to purify water, gas ( toxic ) There are more than 110 elements; 92 are natural Compound - made of two or more elements/atoms chemically combined. Water: H2O, Carbon dioxide: CO2, Sodium chloride: NaCl

9-1 Composition of Matter Substance – can be an element or a compound but it cannot be broken apart by physical means and it can only be split by a chemical reaction. Mixture – made of two or more substances that are NOT chemically combined so they can be separated by physical processes (heating, sifting, settling) They are not always in the same ratio or % composition. Examples: concrete, flavored grits, tea, Kool-Aid, soft drinks, blood, air, dry soup mixture, soup, fruit cocktail, instant cocoa.

Types of Mixtures Homogeneous mixtures – substances are evenly spread out; also known as SOLUTIONS. Ex – Kool-Aid, tea, vinegar, syrup, soft drinks. Heterogeneous mixtures – different materials can be distinguished. Ex – vegetable soup, fruit cocktail, concrete, grits. Colloid – a heterogeneous mixture that “never settles”. Ex – milk, gelatin “Jello”, fog, smoke, whipped cream Suspension – heterogeneous mixture in which visible particles “settle” in the liquid. Ex – muddy water, Italian dressing, liquid butter, some medicines.

9-2 Smog – Environmental Mixture Smog ( smoke+fog) is a form of air pollution; is a colloid of small invisible pieces of solid materials mixed with gases in the air. It is made of dust such as soil, ash from volcanic eruptions, soot from coal and auto exhausts, from industries and forest fires. The solid particles will mix with the moisture in the air (fog) to form the smog. When light hits the dust and water droplets in the air it is scattered and creates the “Tyndall effect”, causing a hazy appearance in the atmosphere.

9-3 Describing Matter Physical Properties – characteristics that you can observe without changing the substances that make up the material. Ex: size, shape, color, state, length, temperature, odor, magnetism, density, melting / boiling point. Physical change – a change that does not change the identity of the substance, just changes in the physical properties.

Describing Matter ( cont. ) Chemical Properties – characteristics of a substance that indicate if it can undergo a certain change; whether it is flammable, combustible, if it will rust, or if it is toxic. Chemical Change – a change of one substance to a different substance. It is usually indicated by various signs such as odors, foaming, explosions, and color changes.

Describing Matter The Law of Conservation of Mass – The mass of all substances present before a chemical reaction equals the mass of the substances remaining after the chemical reaction. Matter can not be created or destroyed, it simply changes from one form to another. If you measure the mass of a log before burning, and could capture all the smoke, gases, ashes, and soot when the log burns, they would have the same mass as the log before burning. This is true for any substance that changes form.