Elements, Compounds and Mixtures

This presentation by Hooria Shahzad is about elements,compounds and mixtures. About their properties, composition and their differences.

1. ELEMENTS, COMPOUNDS & MIXTURES BY: HOORIA SHAHZAD

2. WHAT ARE ELEMENTS ? ELEMENT : is a substance made up of only one kind of atom. cannot be broken down into simple substances by physical or chemical means. have same atomic number. 118 elements are known. are represented by symbols.

3. EXAMPLES OF ELEMENTS DIAMOND COPPER NEON GAS

4. PERCENTAGES OF NATURALLY OCCURING ELEMENTS IN EARTH’S CRUST,OCEANS AND ATMOSPHERE CRUST OF EARTH OCEANS ATMOSPHERE Oxygen 47% Oxygen 86% Oxygen 21% Silicon 28% Hydrogen 11% Nitrogen 78% Aluminium 7.8% Chlorine 1.8% Argon 0.9

5. WHAT ARE COMPOUNDS? COMPOUND : is a substance made up of two or more elements chemically combined together. lose their original properties and produce new substances. can be broken down into simpler type of matter by chemical means but not by physical means. has different properties from its component elements.

6. EXAMPLES OF COMPOUNDS

7. CLASSIFICATION OF COMPOUNDS Compounds can be classified as ionic or covalent. Ionic compounds do not exist in independent molecular form. They form a three dimensional crystal lattice, in which each ion is surrounded by oppositely charged ions. These oppositely charged ions attract each other strongly, as a result ionic compounds have high melting and boiling points. A molecule is a true representative of the covalent compound and its formula is called molecular formula. A molecular formula is a chemical formula that shows the number and kinds of atom in a molecule.

8. SOME COMMON COMPOUNDS WITH THEIR FORMULAE COMPOUND CHEMICAL FORMULA Silicon dioxide (Sand) SiO 2 Sodium hydroxide (Caustic Soda) NaOH Ethane C 2 H 6 Calcium oxide (Quick Lime) CaO Calcium carbonate (Lime Stone) CaCO 3 Urea NH 2 CONH 2 Benzene C 6 H 6

9. WHAT ARE MIXTURES ? MIXTURE : is an impure substance made up of two or more elements physically combined together. c an be broken down by physical means. no chemical changes take place. s ubstances held together by physical forces . The properties of an elements in a mixture r emain same. has no formula.

10. EXAMPLES OF MIXTURES SALAD SOIL SOUP

11. TYPES OF MIXTURES THERE ARE TWO MAJOR TYPES OF MIXTURES: A Heterogeneous Mixture has differences throughout a sample. EXAMPLES: salt, pepper, cereal, rocks A Homogeneous Mixture is the same throughout a sample. EXAMPLES: salt water solution, iodine, vinegar HETEROGENEOUS HOMOGENEOUS Means “different” Means “the same”

12. MIXTURES VS. COMPOUNDS COMPOUNDS MIXTURES DEFINATION It is formed by the chemical combination of atoms of the elements. Mixture is formed by the simple mixing up of the substances. PROPERTIES In compounds the elements lose their original properties and form new substances which are entirely different from them. In mixtures the properties of an element remain same. COMPOSITION Compounds always have a fixed composition by mass. Mixtures do not have fixed composition. JOINED OR NOT The components cannot be separated by physical means. The components can be separated by physical methods. MELTING POINTS Compounds have sharp and fixed melting points. Mixtures do not have sharp and fixed melting points.

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