14.3 Composition of Matter Mixtures

Essential Question What Properties Do Solutions Have? Main Idea Mixtures are made up of two or more pure substances that are not chemically combined. Mixtures can be heterogeneous or homogeneous. Solutions are a type of homogeneous mixture. I.) Mixtures A. A mixture is made up of two or more substances that are not chemically combined. B. Each substance keeps its original properties. 1. Ex: Vegetable soup, trail mix, soil, concrete, fruit salad

C. A mixture does not have a definite compositon (unlike compounds) and cannot be represented by a chemical formula. D. Most matter is in the form of mixtures. E. Mixtures can be classified as homogeneous or heterogeneous 1. A heterogeneous mixture is unevenly mixed a. You can usually tell a mixture is heterogeneous by looking at it b/c you can see the different components.

2. A homogeneous mixture – is evenly mixed a. It appears to be made up of only one kind of matter b. Ex: air – made up of nitrogen, oxygen, and small amounts of other gases (CO 2 & H 2 O) c. Ex: salt water – water and salt d. Ex: steel (a solid) made up of iron, carbon and other elements

II.) Solutions A. Solutions are mixtures that are evenly mixed at the molecular level. 1. You can not see the particles that make up a solution. 2. Solutions have 2 parts: a solute and a solvent a. A solute is the substance that is present in the lesser amount b. A solvent is the substance present in the greater amount. Ex: sugar water

3. Substances that make up a solution keep their properties and can be separated. 4. most mixtures are made up of a liquid solvent and a solid solute a. Ex: water = has dissolved gases and minerals b. Ex: brass = a solid mixture of zinc and copper 5. The concentration of the solution – is the ratio of solute to solvent a. The ratios may vary in a solution

III.) Rate of Dissolving A. Dissolving takes place only at the surface of the solute where the solvent molecules come in contact with the solute particles. B. Dissolving increases with increased surface area of the solute and increasing the temperature of the solvent. 1. How to increase the surface area of the solvent: a. Ex: small piece of sugar dissolves faster than a sugar cube C. Saturated Solution – occurs when no more solute can be dissolved

IV.) Alloys A. An alloy is a solution of one or more metals and other solids. 1. alloys are made when the component substances are melted and mixed. a. Brass = 70% copper and 30% zinc b. Bronze = 90% copper and 10% tin c. Stainless Steel = 74% iron, 18% chromium, and 8% nickel d. Sterling Silver = 93% silver and 7% copper

2. Alloys are useful b/c they have different physical properties than the substances they are made of. a. Ex: Bronze = is harder than copper and more durable = also melts at a lower temperature which makes it easier to work with b. Ex: Steel is the combination of iron and carbon 1. the more carbon present in steel, the stronger the steel 2. the less carbon present in steel, the softer the steel

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