Little Miss "Element": An Overview of Elements, Compounds, and Mixtures

1. Chapter 2 Elements, Compounds, Mixtures

2. An Overview

3. Introducing Little Miss “Element” Hi! I am Little Miss “Element” I am PURE SUBSTANCE I cannot be broken down into any simpler substance by means of a chemical reaction* or electricity**! *Chemical process refers to chemical reaction or heat **Electricity refers to electrolysis

4. Elements Definition of an element: An element is a pure substance which cannot be split up into two or more simpler substances by chemical means. Sugar is not an element as it can be broken down into carbon and water.

5. Elements Note that an element: • Consists of only one kind of atom, • Cannot be broken down into a simpler type of matter by either physical or chemical means • Can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen).

6. Examples of elements Elements are made up of tiny particles Elements can be further classified into two groups: Molecules Atoms Is made up of two or more atoms that are chemically bonded together (note: these atoms are of the SAME element!!) Is the smallest particle of an element and has the same chemical properties of the element Hi, I am from the “Noble gas” family and I work alone We same same!!

7. Cu Na He O O O H H These are elements! Atoms of same element Molecules of same element Hydrogen gas element copper element helium element ozone sodium element

8. Atoms An element is made of tiny particles called atoms. The atoms of an element is different from that of another element.

9. Elements- Atoms Consists of only one kind of atom Microscopic view of the atoms of the element argon (gas phase).

10. Na H Cl What is an atom? Examples of models of atoms: Hydrogen atom Sodium atom Chlorine atom

11. For example, hydrogen is H2. Ozone is O3. Molecules Very few elements exists as atoms besides elements such as helium and neon. Most elements exist as molecules.

12. Hydrogen (H2) is a diatomic molecule. Ozone (O3) is a triatomic molecule. Molecules consisting of a few atoms are called polyatomic molecules.

13. Elements-Molecules Consists of only one kind of atom Microscopic view of the molecules of the element nitrogen (gas phase).

14. O O O O H H O Examples of molecules (elements) S S S S S S S N N S

15. Chemical Symbols of Elements Chemists use symbols to represent elements. For example, O represents oxygen while Fe represents iron. Know Chemical Symbols in Table 1 on page 58

16. Classification of Elements – Metals and Non-metals There are two major groups of elements – metals and non-metals. Iron is a metal. Oxygen is a non-metal. Metals and non-metals are grouped separately on the Periodic Table. There are some elements called metalloids which behave like both metals and non-metals.

17. What is an element? An element is a substance that cannot be broken down into two or more simpler substances by any chemical means. - They are arranged in the Periodic Table, classified as metals and non-metals. - They may consist of atoms of same element or molecules of the same element. Non-metals (including hydrogen) Metals (excluding hydrogen)

18. Summarising Elements Metals Non Metals Atoms Atoms Molecules

19. Compounds Note that a compound: • can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means), • has properties that are different from its component elements, and • always contains the same ratio of its component atoms.

20. Cu H H What is a compound? A compound is a substance which is made up of two or more elementschemically combined together. • Chemical reactions taking place. Qn: Is this a compound? Qn: Is this a compound? Qn: Is this a compound? O It only contains one type of element. It only contains one type of element. O It is not chemically combined. H H O

21. O N H H H H H So, what is a compound then? Water Ammonia gas Consists of two or more elements And They are chemically combined together!

22. Compounds Microscopic view of the molecules of the compound water (gas phase). Oxygen atoms are red and hydrogen atoms are white.

23. Making compounds from their elements Example: Making water (picture) lighted splint ELEMENTS COMPOUND hydrogen (colourless gas) oxygen (colourless gas) heat, light and explosion water (colourless liquid) Example: Making water (models) mixture of hydrogen and oxygen water heat, light and explosion Water molecule Hydrogen molecule Oxygen molecule

24. Making compounds from their elements Example: Making iron sulphide compound compound elements heat Iron + sulphur  iron sulphide +  heat yellow grey black

25. Summarizing • A compound is made up of two or more elementschemically joined together • A compound has a fixed composition • Every compound has a unique chemical formula • A compound has a completely different properties from its elements • A chemical reaction (decomposition or electrolysis) is needed to separate the elements in the compound

26. S S S S O O S N N S S S H O O O H N H C H H Molecules- Elements or compounds? • A molecule consists of two or more atoms of the same element, or different elements, that are chemically bound together. • It can be a molecule of an element • E.g. N2, O2, S8 • It can be molecule of a compound. • H2O, CO2, NH3

27. AIR Introducing Little Mr. “Mixture” Burp!!!! I am messy! I am formed when two or more substances joined together physically (without chemical bonds) I have the same properties as all the substances I am his best friend!

28. Mixtures Definition of a mixture: A mixture is not a pure substance as it contains a mixture of atoms of molecules which are not chemically combined together.

29. Mixtures • Note that a mixture: • consists of two or more different elements and/or compounds NOT chemically combined. • Can be homogeneous or non-homogeneous • can be separated into its components by physical means, and • often retains many of the properties of its components.

30. Mixtures Microscopic view of a gaseous mixture containing two elements (argon and nitrogen) and a compound (water).

31. Mixtures • Examples of mixtures include muddy water and air. Air is made up of gases such as nitrogen and oxygen mixed together.

32. Little Mr “Mixture” I do not have a fixed composition of the substances. • A Mixture can be: • element + element • element + compound • compound + compound • (Refer to page 59, Fig 4.7) He is a “boo-boo!” He can be separated to its substances by physical methods

33. A mixture of 2 elements A mixture of two elements, e.g. neon (Ne) and hydrogen (H2)

34. A mixture of 1 element and 1 compound A mixture of one element and one compound, e.g. hydrogen (H2) and ammonia (NH3)

35. A mixture of 2 compounds A mixture of two compounds, e.g. water vapour (H2O) and carbon dioxide (CO2)

36. Difference between mixtures and compounds.

37. Difference between mixtures and compounds.

38. Difference between mixtures and compounds.

39. Difference between mixtures and compounds.

40. Laugh what? I know I am a little “bushy and hairy” than you… Differences between mixtures and compounds *giggles* HeE stupid… VS Mr Messy Little Miss Compound

41. Comparison between mixtures and compounds Mixture Compound Separation /breakdown Components can be separated by physical methods Elements in a compound Cannot be separated by physical methods Properties (chemical / physical) Same properties as its components Properties are unique and different from its elements Energy Change No chemical change takes place when a mixture in formed A chemical reaction takes place when a compound is formed

42. Challenge Time • Is mineral water an element, mixture or compound?

43. Challenge Time • Are YOU an element, mixture or compound?

44. EXTRA! • Human body is made up of 28 elements? • About 99% our mass is made up of the 6 main elements • Oxygen (65%) • Carbon (18%) • Hydrogen (10%) • Nitrogen (3%) • Calcium (1.5%) • Phosphorus (1.5%)

45. The End……