Unit 1 Elements, Compounds, and Mixtures

1. Unit 1Elements, Compounds, and Mixtures

2. Mixtures, elements, compounds • Scientists like to classify things. • One way that scientists classify matter is by its composition. • Ultimately, all matter can be classified as mixtures, elements and compounds.

3. Elements

4. What is an element? • An element is a pure substance that cannot be separated into simpler substances by physical or chemical means. • A pure substance is a substance in which there is only one type of particle. • The particles of pure substances are exactly alike no matter their size or where they are found.

5. Element Element Substance that contains only 1 type of atom Examples: H, He, O, B … anything from periodic table--> that’s why it’s called the periodic table of elements

6. 90 different elements found in nature, the others are man-made

7. Every element has a unique set of properties • An element is identified by its unique set of properties. • These properties can be physical or chemical properties. • These properties do not depend on the amount of the element present.

8. Properties of Elements • Properties are not unique to the element. • Ex. He & Kr are both gases but have very different densities. He is lighter (less dense) than air while Kr is heavier (more dense) than air

9. Elements are classified by their properties • Elements are classified into groups according to their similar properties. • For example, elements that are shiny are classified into a group called metals. • You can predict some of the properties of an unfamiliar element by knowing the category to which it belongs.

10. The Three Major Categories of Elements • Metals • Non-metals • Metalloids • Metals are elements that are shiny and are good conductors of thermal energy and electric current. They are malleable and ductile. • Non-metals are elements that are not shiny, poor conductors of thermal energy and electric current. They tend to be brittle and non-malleable. • Metalloids are also called semi-conductors. These elements have the properties of metals and non-metals.

11. Why isn’t it a good idea to classify matter by its phases? • Because one kind of substance can exist in more than one phase – such as H20. And matter changes phases rather easily.

12. Why isn’t matter classified according to its physical characteristics, such as color? • Scientists wouldn’t find it very useful to group gold, sunflowers, and the sun together.

13. Atoms • The basic component of all matter. • The atom is the smallest particle of an element that has all of the chemical properties of that element. • Atoms consist of a nucleus of protons and neutrons surrounded by electrons. http://www.ktf-split.hr/glossary/image/atom.gif

14. Elements • A substance consisting of a single type of atom. • It cannot be broken down into different kinds of matter. http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/handouts/helium.GIF http://www.rentrain.com/resources/Helium%20Safety.jpg

15. Molecules • Compound of two or more atoms, the smallest unit of chemical compounds. • The smallest particle of a substance that has all of the physical and chemical properties of that substance. http://www.awwu.biz

16. Compounds • Most elements are not found alone in nature, but rather combined with other elements. • A compound is a pure substance composed of two or more elements that are chemically combined. • To be chemically combined, the elements in the compound need to have reacted with one another. • Most substances you encounter are compounds!

17. Every compound has a unique set of properties • Each compound has a unique set of properties that allows you to distinguish it from other compounds. • A compound has different properties from the elements that form it. • For example, table salt (NaCl), is made up of sodium and chloride, two dangerous elements on their own! • Observe how sodium and chlorine react to form salt! sodium chloride table salt + =

18. Properties: compounds vs elements • Properties of the compound can be very different from the properties of the individual elements that make up the compound • Na is a silvery, white metal that is explosive when combined with oxygen • Cl is a poisonous greenish-yellowish gas • NaCl is a white solid that is great on french fries.

19. Compounds can be broken down into simpler substances • Some compounds can be broken down into elements through chemical changes. • Some compounds are simply broken down into simpler compounds through chemical changes. • You cannot break a compound down through a physical change!!!

20. Breaking down compounds • Usually energy is necessary for a chemical change to happen • Apply heat • Apply electric current

21. Compounds in your world • Compounds are found in nature and industry. • Proteins are compounds that are found in all living things. They are all composed of nitrogen and other elements. • Carbon dioxide is another important compound. • In industry, compounds are often synthetically created.

22. Combinations of Elements:Compounds • A substance formed from two or more elements, with a fixed ratio determining the composition. • The elements lose their individual chemical properties and the compound has new properties. http://www.awwu.biz

23. Formulas Glucose -C6H12O6 • The formula which identifies the atoms and the number of each kind in the molecules of a compound. • The number and types of atoms in a molecule.

24. Formulas 6C6H12O6 Elements in the compound: Carbon Hydrogen Oxygen

25. Formulas:Subscripts 6C6H12O6 # of atoms of each element in a molecule of the compound: Carbon - 6 Hydrogen - 12 Oxygen - 6

26. Formulas:Coefficients 6C6H12O6 # of molecules: 6 molecules of glucose

27. Mixtures • A mixture is a combination of two or more substances that are not chemically combined. • Two or more substances together form a mixture if they do not react to form a compound. • Substances in a mixture retain their identity, they do not change into something else. • Mixtures can be physically separated through physical change. Ex: picking the pecans out of pecan pie, boiling salt water to remove the salt.

28. Combinations of Elements:Mixtures • A substance consisting of two or more substances mixed together. • Mixtures can usually be separated by mechanical means. • Two or more substances mixed together in such a way that each remains unchanged. http://www.seelecttea.com/

29. Notice the two types of mixtures, heterogeneous and homogenous. Suspensions, Solutions and Colloids are all considered mixtures. This is an important chart because it shows you visually how mixtures are categorized. The Big Picture

30. Common Techniques For Separating Mixtures • Distillation • Magnet • Centrifuge • Multiple Steps • Distillation is the process of separating a mixture through boiling. • Magnets can be used to separate a mixture by attracting the substance that is magnetic. • A centrifuge is a machine that separates a mixture according to the substances different densities. • Some mixtures can only be separated by multiple different steps.

31. Solutions • A solution is a mixture that appears to be a single substance but is composed of particles of two or more substances that are distributed evenly amongst each other. • Solutions are described as homogenous mixtures because they have the appearance of a single substance. • When substances are dissolved, the substance being dissolved is known as the solute and the substance into which it is dissolved is known as the solvent. • Soluble or insoluble? • We think of solutions as liquids, but they can also be gases (air) or solids (steel).

32. Solute vs solvent • Solute: the substance that dissolves in the solvent, must be soluble in the solvent. • Solvent: the substance in which the solute dissolves • Ex: sweetened tea • Solute is the sugar • Solvent is the tea

33. alloys • Not all solutions are liquid • Alloy are solid solutions of metals or nonmetals dissolved in metals • Steel is an alloy of nonmetal carbon dissolved in iron • An alloy is a homogeneous hybrid of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. • The resulting metallic substance usually has different properties (sometimes substantially different) from those of its components.

34. More about solutions… • Particles in a solution are extremely small. • This means that you may not see a cloudy mixture, it may look as if it is all one substance. That is because the particles are so small.

35. Heterogeneous Mixture Heterogeneous mixture Least mixed mixture does not appear to be the same throughout. Parts are easy to recognize and separate. Examples: granite, tacos, bowl of cereal, big Mac, Italian salad dressing, concrete, crunchy peanut butter, sandwich….

36. Homogeneous Mixture Homogeneous mixture Well-mixed, appears to be the same throughout. Particles are small, not easily recognizable and do not settle when the mixture is allowed to stand. Examples: glass, stainless steel, sugar dissolved in water…

37. A measure of the amount of solute dissolved in the solvent is known as the concentration of a substance. Knowing the exact concentration in a solution is very important in chemistry and in life. Dilute or concentrated? Expressed in grams per mL. Solubility refers to the amount of solute needed to make a saturated solution using a given amount of solvent. Ex: sugar in lemonade Expressed in grams per 100 mL. Concentration and Solubility

38. Concentration EX: “from concentrate” Solubility EX: “sweet, sweet lemonade” Concentration and Solubility

39. solubility • If you add too much sugar to a glass of iced tea, not all of the sugar dissolves • The maximum amount of sugar that can be dissolved depends on the solubility of the sugar at a certain temperature

40. temperature • Most solids are more soluble in liquids at higher temperatures • Gases become less soluble in liquids as the temperature is raised • Soft drinks go flat faster when warm. The gas that is dissolved in the soft drink cannot stay dissolved when the temperature increases.

41. Dissolving solids faster in liquids • Mixing or stirring- causes solute to separate from one another • Heating- causes solute to move more quickly • Crushing- increases the amount of contact the solute has with the solvent

42. What affects how quickly solids dissolve in liquids? • Most of the solutions that you are familiar with are of a solid dissolved in a liquid. • Several factors affect how quickly the solute will dissolve. • Mixing – stir or shake to make particles spread out more evenly and to speed up dissolving. • Heating – this causes particles to move more quickly thus speeding up the process of dissolving. • Crushing – crushing or grinding up the solute increases the amount of contact b/t the solute or solvent and increase how quickly the dissolving takes place.

43. Suspensions • A suspension is a mixture in which particles of the material are dispersed throughout a liquid or gas but are large enough that they settle out. • The particles in a suspension are insoluble, so they settle out. • Suspensions are called heterogeneous mixtures b/c the different components are easily seen. • Ex: snow globe, muddy water, salad dressing • Suspensions can be separated by passing them through a filter.

44. Colloids • A colloid is a mixture that has the properties of both a solution and a suspension. • A colloid is a mixture in which the particles are dispersed throughout but are not heavy enough to settle out. • Examples: Jello, milk, fog, mayonnaise, stick deodorant, whipped cream

45. colloids • The particles in a colloid are much smaller than the particles in a suspension. • Particles are large enough to scatter light. • Colloid can not be separated by filtration • Particles are so small they can pass through a filter

46. One Element The Same Element (Gas) (Solid)

47. Another element A mixture of two elements This one likes to go round in pairs as a gas (molecules)

48. This is not a mixture, it is a COMPOUND of two different elements This is just a mixture of two elements

49. Element, Compound or Mixture ?

50. Element, Compound or Mixture ? Element