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Substances, Mixtures, Solubility. Chapter 21. Section 1: Substances . A substance is matter that has the same fixed composition and properties. Identity can be changed by chemical processes but not by physical processes. Elements.
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Substances, Mixtures, Solubility • Chapter 21
Section 1: Substances • A substance is matter that has the same fixed composition and properties. • Identity can be changed by chemical processes but not by physical processes.
Elements • An element is an example of a pure substance, it can NOT be broken down into simpler substances.
Compounds • A pure substance composed of two or more elements that chemically combine.
Compounds • Compounds also have fixed compositions. • The ratio in a compound is always the same. • Example: Water
Join in definite ratio • Ratio is according to the mass sizes. • Water is hydrogen and oxygen • 1 gram of hydrogen for every 8 grams if oxygen • 1:8 mass ratio of hydrogen to oxygen
To Form a Compound • The atoms must chemically combine through a Chemical Change! • Two or more elements react with one another.
Unique Set of Properties • Boiling Point • Melting Point • Density • Color • Reactivity with acid • Reacts when exposed to light
Breaking Down a Compound • Heat • Electric Current • Chemical Reaction
Common Compounds In Industry - Ammonia -Medicines -Food Preservatives -Synthetic Fibers • In NATURE • Carbon Dioxide • Sugar • Proteins • Water • Sea Shells- Calcium • Quartz
Mixtures • Mixtures are combinations of substanes that are not bonded together and can be separated by physical processes.
Mixtures • Unlike compounds, mixtures do not always contain the same proportions of the substances that they are composed of. Example: Lemonade
Mixtures • A heterogenous mixture is a type of mixture where the substances are not mixed evenly. • Example: Seeds in a watermelon
Mixtures • A homogenous mixture contains two or more substances that are evenly mixed on a molecular level but still are not bonded together. • Kool-aid
Mixtures • Another name for a homegenous mixture is a solution.
How does a solid solution form? • The substance that dissolves-or seems to disappear- is called the solute. • The substance that does the dissolving (or there is more of it) is called the solvent.
Precipitate • A precipitate is the solid that forms as a result of a chemical change. • Soap Scum
Liquid Solutions • In liquid, the solvent is a liquid. • Carbonated drinks are liquid-gas solutions. Carbon Dioxide is the gaseous solute and water is the solvent. • In liquid-liquid solutions, both solvent and solute are liquids.
Gaseous Solutions • In gaseous solutions, a smaller amout of one gas is dissolved in a larger amount of another gas. • The air you breathe is a gaseous solutions.
Solid Solutions • In solid solutions, the solvent is a solid. The solute can be a solid, liquid, or gas. • Brass and Steel are common solid solutions.
Solubility • Water is the universal solvent. • A solution in which water is the solvent is called an aqueous solution.