TEKS

2. TEKS • describe heterogeneous and homogeneous mixtures.[.6D] • explain the similarities and differences between heterogeneous and homogenous mixtures.[.6E] • identify chemical examples of pure substances and mixtures.[.6F]

3. Basic Chemistry Principles

4. Tuesday

5. Pure Substances • Can be formed from elements or compounds • Consist of only one component with definite physical and chemical properties • Have the same composition throughout • Example: O2 or pure water

6. Elements • Are pure substances consisting of one type of atom • Cannot be broken down or changed into another substance • Combine with other elements to form compounds

7. Compounds • Are substances composed of two or more elements in specific ratios and bonded together through chemical forces • Example: Carbon dioxide is always composed of one carbon atom and two oxygen atoms • Are classified as either covalent or ionic

8. Common Compounds • Salt -Sodium chloride- NaCl • Baking Soda -Sodium bicarbonate – NaHCO3 • Caffeine – C8H10N4O2 • Aspartame – C14H18N2O5

9. Mixtures • Are substances held together by physical forces • this means individual molecules are near each other without altering their chemical structure • Can be homogeneous or heterogeneous

10. Mixtures & Pure Substances Example • Tap water contains molecules which are not water molecules,making it a mixture • Distilled water containsonly water molecules making it a pure substance

11. Homogeneous Mixture • Homogeneous: mixtures which are the same throughout, with identical properties throughout the mixture • Is also called a solution

12. Heterogeneous mixture • Heterogeneous: mixtures which have different properties when sampled from different areas • Different types of heterogeneous mixtures • Colloid • suspension

13. Colloid • A colloid is a homogenous mixture that contains large Particles Example: Milk

14. Suspension • A type of heterogeneous mixture whose particles settle out over time and can be separated from the mixture on standing

15. MATTER yes no Can it be physically separated? MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be chemically decomposed? Homogeneous Mixture Heterogeneous Mixture Compound Element Suspensions Colloids Solutions

16. Wednesday

17. Properties of Matter Physical and Chemical Properties Chemical Properties Physical Properties Reactions in the presence of Water, Air, Acid, Base What happens when heated Extensive Properties Depends on the amount _______________ Mass, Volume, Length, Shape Intensive Properties Do NOT depend on the amount ________________ E.G Color, Taste, Melting/Boiling Point, Luster, Hardness

18. Physical Changes • Are any changes not involving a change in a substance’s chemical identity • Occur when objects undergo a change that does not change their chemical nature • Involves a change in physical properties • physical properties include the following: • texture • shape • size • color • volume • mass • weight

19. Common Physical Changes in Food • Include the following: • cutting • mashing • boiling • melting • freezing

20. Freezing • Involves storing a food below the freezing point of water • safest temperature of freezer storage is below 0°F • Results in water transforming from a liquid state to a solid • Can have adverse effects on food quality • texture change, especially if food is not frozen quickly • altered color • freezer burn if exposed to air • increased food preparation time to account for defrosting time

21. Chemical Changes • Occur when bonds are broken and new bonds are formed between different atoms • Take place in everyday food production • Include the following common food reactions: • Non-enzymatic browning • leavening • fermentation

22. Non-Enzymatic Browning • Is browning caused by heat degradation of sugars or by the reaction between reducing sugars and a free amino group • Is commonly found in foods • Increases when there is a rise in temperature and with a rise in pH above 6.8

23. Leavening • Gives breads, cakes, muffins, pancakes and other foods the ability to rise and increase in volume • Occurs mainly during cooking • Involves a water or gas expanding for rising to occur

24. Leavening • Agents include: • baking powder • baking soda • baker’s ammonia • potassium bicarbonate • yeast • sourdough starter

25. Fermentation • Is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts or bacteria under anaerobic conditions • Implies the action of microorganisms is desirable • Is used in preservation techniques to create lactic acid in sour foods or for use in pickling foods

26. Separating Mixtures • Because mixtures are physically combined, the processes are used to separate themare based on the difference in physical properties of the substances. • 4 methods for separation

27. Filtration • Uses a porous barrier to separate a solid from a liquid

28. Distillation • Based on differences in boiling points of the substances • Heat mixture until substance with lowest boiling point boils to a vapor which is then condensed into a liquid

29. Crystallization • Results in formation of pure solid particles of a substance from a solution containing the dissolved substance

30. Chromatography • Separates the components of a mixture (called the mobile phase) on the basis of the tendency of each to travel or be drawn across the surface of another material (called the stationary phase)

31. 3.4 Elements and Compounds TEKS • 4. (D) Classify matter as pure substances or mixtures through investigation of their properties.

32. Chapters

33. Goals & Objectives • Explain the Periodic Table of the Elements • Identify and explain how chemical symbols, formulas and equations are used in food science • Discuss elements, compounds, mixtures and formulas • Compare elements and compounds • Analyze chemical and physical changes in food • Examine the occurrence of specific chemical reactions