1. Elements, Compounds, and Mixtures

2. Elements, Compounds, and Mixtures Chapter 9 – Section 1  Element: a substance that cannot be separated or broken down into simpler substances by chemical or physical means  Pure substance : a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. Each element contains atoms. It only has one type of particle or atom.  Each element has its own characteristic properties. Does not matter how much of the element is present. Characteristic properties include—physical properties: boiling point, melting point, and density and chemical properties: reactivity with acid. Elements may share certain properties. Look at elements on page 235.  http://www.science.co.il/PTelements.asp?s=Density http://www.science.co.il/PTelements.asp?s=Density

3. Elements, Compounds, and Mixtures Chapter 9 – Section 1  Elements are grouped into categories.  Metal : an element that is shiny and that conducts heat and electricity well  Nonmetal : an element that conducts heat and electricity poorly, non-shiny, solids tend to be brittle and unmalleable.  Metalloid : also called (semi-conductors) an element that has properties of both metals and nonmetals. Some are shiny and some are dull. Some are malleable and some are ductile. Also, some conduct heat and electricity well.  By knowing what category an element is in you can predict how it will react/behave.

4. Section 2  Compound: a substance made up of atoms of two or more different elements joined by chemical bonds.  Molecule: A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds. H 2, N 2, O 2 are molecules. H 2 O, C 6 H 12 O 6, and CH 4 are compounds.  Elements combine by reacting or undergoing a chemical change.  http://www.youtube.com/watch?v=OuFqtxZJRvM http://www.youtube.com/watch?v=OuFqtxZJRvM  Elements join in specific ratios. 8:1 for water. 8g of Oxygen for every 1g of Hydrogen. This is mass ratios. Also, can find element ratios.

6. Section 2  Compounds properties differ from those of single elements. Ex. Na, Cl, NaCl or Al + O  Al 2 O 3  Chlorine = dangerous gas and Na reacts violently with water, however, NaCl dissolves in water and does not explode.  http://www.youtube.com/watch?v=DgdtDSP9RPg http://www.youtube.com/watch?v=DgdtDSP9RPg  http://www.youtube.com/watch?v=6BK-ZU_nNXQ http://www.youtube.com/watch?v=6BK-ZU_nNXQ  http://www.youtube.com/watch?v=dmcfsEEogxs http://www.youtube.com/watch?v=dmcfsEEogxs  http://www.youtube.com/watch?v=ODf_sPexS2Q http://www.youtube.com/watch?v=ODf_sPexS2Q

7. Section 2  Breaking down compounds: sometimes they break down into simpler compounds. Sometimes these can be broken down to simple elements. Carbonic Acid  H 2 CO 3 or C 6 H 12 O 6  If a compound is broken down a chemical change has occurred. Heat and/or electricity can induce decomposition of a compound.  Compounds are all around us. Can you name some?

8. Elements, Compounds, and Mixtures Chapter 9 – Section 3  Mixture : a combination of two or more substances that are not chemically combined. Ex: pizza, orange juice, salad dressing. In a mixture there is no chemical change. Each component has its same composition as it did before the mixture. NO CHEMICAL CHANGE IN A MIXTURE!  Pg. 244 difference between compounds and mixtures.  Rocks are mixtures---conglomerate.

9. Mixtures vs. Compounds  Mixtures  Made of elements, compounds, or both.  No change in original properties of components.  Separated by physical means.  Formed using any ratio of components.  Compounds  Made of elements  Change in original properties of components  Separated by chemical means  Formed using a set ratio of components

10. Ways to Separate a Mixture  Distillation: separates a mixture based on boiling points of the components—ex: boil salt water to separate salt from water.  Magnet: can separate a mixture of aluminum and iron elements.  Centrifuge: Separates mixtures based on the densities of the components. Blood cells and plasma---plasma is less dense than the blood cells.  Filtration: you can filter the substances. Thicker elements will stay in the filter.

12. Section 3  Solution : a homogeneous mixture of two or more substances uniformly dispersed throughout a single phase. Does not have to be a liquid…a nickel is a combination of copper and nickel. It appears to be a single substance.  A heterogeneous mixture would have phases—two or more regions that differ in properties—ex: oil and vinegar.  When particles spread evenly throughout a mixture it is known as dissolving.  Solute : in a solution, the substance that dissolves in the solvent…ex: salt. A solute must be soluble---able to dissolve. If it is insoluble it forms a mixture that is not a solution.  Solvent : in a solution, the substance in which the solute dissolves….ex: water

15. Elements, Compounds, and Mixtures Chapter 9 – Section 3  Concentration : the amount of a particular substance in a given quantity of a mixture, solution, or ore. Basically, the amount of solute dissolved in a solvent. Can be expressed as g/ml.  Dilute: contains the same amount of solvent but less solute. Concentration of solute to solvent is small.  Concentrated: Has a large ratio of solute to solvent. Does not tell specific amount. Ex: 100g of sugar to 100g of water is more concentrated than 10g of sugar to 100g of water. But 10g of sugar in 100g of water is more concentrated than 1g of sugar in 100g of water.  Solubility : the ability of one substance to dissolve in another at a given temperature and pressure

17. Section 3  Gases become less soluble as temperature is increased.  Things that can affect how fast solids dissolve:  Mixing: stirring or shaking—solute spreads out faster.  Heating: causes particles to move quicker.  Crushing: solute increases its contact are with solvent.  Types of mixtures:  Suspension : a mixture in which particles of material are more or less evenly dispersed throughout a liquid or gas. If allowed to sit the particles will settle out…snow globe.  Colloid : a mixture consisting of tiny particles that are intermediate in size between those in solutions and those in suspensions and that are suspended in a liquid, solid, or gas. They do not settle out like those in a suspension and are generally smaller than particles in a suspension.