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1.2 Chemical Compounds

1.2 Chemical Compounds

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1.2 Chemical Compounds

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  1. 1.2 Chemical Compounds

  2. Elements • Recall that elements are just one typeof atom

  3. Compounds • Compounds are substances made from two or more different kinds of atoms • Most substances you see around you are compounds • Plastics, glass, water, wood, gasoline

  4. Properties of Compounds • Different compounds have very different properties • Remember there are physicaland chemical properties • Try to come up with examples of each

  5. Compound vs. Atoms • The key thing to remember: Properties compounds are different from the properties of the atoms it is made of Ex: Sodium (Na) metal is explosive in water and would surely hurt to eat, while chlorine(Cl)is a poisonous gas that would kill you if inhaled • But salt, sodiumchloride, is tasty on food and totally unreactive with water!

  6. Where do they come from? • Compounds are formed during chemical reactions • Remember the chemical reaction between chlorine gas and sodium metal to produce sodium chloride (salt) • Or the reaction between water and any alkali metal to produce hydrogen gas

  7. Chemical Formula • Compounds can be represented by a chemical formula • It tell the chemist which elements are in the compound • Its also shows how many atoms of each element are present in one unit of compound. • Ex: water, H2O is a compound • There are 2 hydrogen atoms and 1 oxygen atom for every molecule of water

  8. More examples of compounds • Look at the list of compounds onPg.12 • How many of each type of atom are in each compound?

  9. Mixtures • Two or more different substances that are NOT chemically combined • Can be separated by a physical process Ex: Salt water is a mixture -Salt a compound, NaCl dissolved in water, H2O, which is also a compound. Salt and water can be separated by evaporating the salt – a physical process

  10. Particle Pictures • The following particle pictures will help to visualize the difference between elements, compounds and mixtures • You should draw some examples in your notes to help you remember

  11. Element Compound Mixture