Chapter 7 Foundations of Chemistry

1. Chapter 7 Foundations of Chemistry

2. Essential Questions • What is a substance? • How do atoms of different elements differ? • How do mixtures differ from substances? • How can you classify matter? • What are some physical properties of matter? • How are physical properties used to separate mixtures? • How can a change in energy affect the sate of matter? • What happens when something dissolves? • What is meant by conservation of mass? • What is a chemical property? • What are some signs of chemical change? • Why are chemical equations useful? • What are some factors that affect the rate of chemical reactions?

3. What do you already know? • Move to the “true” or “false” side of the room based on your beliefs about the following statements TRUE FALSE The atoms in all objects are the same When wood burns, new materials form The weight of a material never changes, regardless of where it is You cannot always tell by an object’s appearance whether it is made of more than one type of atom When you stir sugar into water, the sugar and water evenly mix Boiling is one method used to separate parts of a mixture Temperature can affect the rate at which chemical changes occur

4. Matter • ___Matter____- Anything that has mass and takes up space. • Everything in the universe that you can see is made up of matter. • Is it matter? • Toaster ____ • Bowl of soup____ • Steam____ • Sound____ • Dust____ • Air____ • Heat____ • Flag____ • Bacteria____ • Light____

5. 1-Classifying matter • A ______________ is matter with composition that is always the same • Ex: Aluminum, water, oxygen, sugar • Two major types of substances • ____________ are substances that consist of just one type of atom • Elements are arranged in the periodic table substance Elements

6. 1-Classifying matter • A substance is matter with composition that is always the same • _____________ are substances containing atoms of two or more different elements chemically bonded together • Atoms are always combined in the same way • Compounds are represented by chemical formulas • H and O are atom symbols • 2 (subscript) tells you how many Compounds

7. 1-Classifying matter • Properties Compounds versus Elements • A compound will have __________________ than the elements that make it up Different properties

8. 1-Classifying matter • What is a mixture? • A _mixture___ is matter that can vary in composition • No chemical reaction • No compound formed • Each substance keeps its original _identity__ • _No Fixed Ratio__— not always the same

9. 1-Classifying matter Homogeneous Heterogeneous not evenly evenly

10. 1-Classifying matter • Homogeneous mixtures are also known as _______________ • Solutes dissolve into solvents • Dissolving means to form a solutionby mixing ___________ solutions evenly

11. 1-Classifying matter • Comparing Mixtures and Compounds elements both No change Change chemical physical any set

12. 1-Classifying matter

13. 2- Physical Properties • A _physical property__of matter can be observed or measured without changing the matter’s __identity_____. • Examples: • __color____ • Melting and boiling points • ___mass____ • Conduct electricity • Strength • Flexibility • State – __solid, liquid, gas__ • Density – the amount of mass in a given volume • _solubility___ • Ductility – ability to be draw into wires • Malleability – ability to be hammered into sheets

14. 2- Physical Properties _Viscosity__ - A liquid’s resistance to flow _Malleability__– Can be hammered into thin sheets

15. 2-Physical Properties • Size-dependent properties • These are properties of matter that depend on the size or amount of matter • Examples: mass and volume • Size-independent properties • These are properties of matter that do not depend on the amount of matter present • Examples: melting point, boiling point, electrical and thermal conductivity, solubility, and density

16. 2- Physical Properties • Mass & Weight • Mass– the amount of matter in an object. • The more matter in the object, the greater the mass • Mass of an object is the same regardless of the object’s location in the universe. • Mass vs. Weight • Mass and weight do NOT have the same meaning. • Weight– the measure of gravitational force exerted on an object. • Will change with location in the universe

17. MASS Measure of the amount of matter in an object Always the same regardless of location in universe Measured using a balance Expressed in grams WEIGHT Measure of gravitational force on an object Changes based on location in the universe Measured using a scale Expressed in Newtons(N) Difference Between Mass and Weight

18. Density • Density is a physical property that describes the relationship between mass and volume. • Density- the amount of matter in a given space or volume. • Basketball vs. bowling ball. • They both are the same size, but the bowling ball has more mass. • Since it has more mass, it has a greater density

19. Density Continued • Denser liquids go to the bottom of the container. • Think of vinegar and oil salad dressing • Density of solids. • Would you rather carry 1kg of feathers or 1kg of lead? • The lead would be much smaller to carry around. • An object will float on water if it is less dense than water • The object will sink if it is more dense than water.

20. Volume • Volume- The amount of space taken up, or occupied, by an object. • Because objects have volume, they cannot occupy the same space at the same time.

21. Liquid Volume • Units for Liquid Volume • L • mL • cm3 • Measuring Liquid Volume • Use graduated cylinder– more accurate • Meniscus – the curve at a liquids surface • Read liquid measurements from the bottom of the meniscus.

22. Volume of a regular shape • Regularly Shaped Objects • Units for solids • cm3 units (having 3 sides) • Volume = length (l) x width (w) x height (h) • Example: What is the volume of a block that measures: • Length: 3 cm Width: 5 cm Height: 7 cm

23. Volume of a regular shape • What is the volume of a box that has a length of 5 cm, a width of 1 cm, and a height of 2 cm? • What is the volume of a box that has a height of 10 cm, a width of 2 cm, and a length of 3 cm?

24. Volume of an irregular shape • Irregularly Shaped Objects • Same units as above • Use water displacement method. • Submerge object in a known amount of water and read the level change. • 1 mL = 1 cm3 • Ex. Graduated cylinder has 25.0 mL of water in it. After Tom places a paper clip in it, the water level rises to 28.6 mL. What is the paper clips volume?

25. Volume of an irregular shape • Initial Volume ___________ • Final Volume ___________ • Volume of object _________ • Initial Volume ___________ • Final Volume ___________ • Volume of object _________

26. 2- Density • To find density, you must first measure the mass and volume of the object. • The formula is: • Density = mass D = m volume V • The unit will be g/cm3 . You may also see kg/m3 or kg/L

27. 2- Density • What is the density of an object whose mass is 25g and whose volume is 10 cm3? • Suppose you have a lead ball whose mass is 454 g and density is 11.35 g/cm3. What is the volume of the ball?

28. 2 - Density • What is the mass of a 15 mL sample of mercury with a density of 13.55 g/mL? • A graduated cylinder contains 25 mL of water. When a 4.5 g paper clip is dropped into the water, the water level rises to 36 mL. What is the density of the paper clip?

29. 2-Density • Combination problem: • You have a substance that has a mass of 96.6g. When you place it into a graduated cylinder, the water rises from 10 mL to 15 mL. • Find the volume of the substance • Find the density of the substance • You think it might be copper (density= 8.96 g/mL) or gold (density =19.32 g/mL). Which material is it?

30. 3- Physical Changes • Physical changes do not form new substances. • A physicalchangeis a change in size, shape, form, or state of matter in which the matter’s identity stays the same • Examples include: • silver shaped into jewelry • Cutting a piece of wood • Tearing a piece of paper • Dissolvingsugar in water • Melting a popsicle

31. 3-Physical Changes • States of matter • Solids have very little energy and vibrate in place • Liquids have a little more energy and slide back and forth • Gases have the most energy and fly all over the place

32. 3-Physical Changes • Conservation of Mass • During a physical change, the physical properties of matter change, but the particles are the same as those present before the change occurred • The mass before a physical change has to be the same as the mass after a physical change

33. 4 - Chemical Properties & Changes • A chemical propertyis a characteristic of matter that can be observed as it changes to a different type of matter • Flammability – ability to burn • Reactivity is the ability of two or more substances to combine to form one or more new substances • Iron combines with water and oxygen to form rust.

34. 4-Chemical Properties and Changes • Physical versus Chemical properties

35. 4-Chemical Properties and Changes • A chemical changeis a change in matter in which the substances that make up the matter change into other substances with new physical and chemical properties • When you bake a cake, you combine flour, sugar, eggs, and several other ingredients. The product is the cake. You cannot unbake the cake and return to the original ingredients.

36. Signs of a Chemical Change • Several signs indicate a chemical change has taken place. These include: • Change in color • Change in odor • production of heat • fizzing and foaming, or bubbling • or formation of a precipitate (solid) • When you bake a cake you smell it baking, you see it browning, and when you cut it open you can see pockets of gas.

37. Color Change Copper will form a patina when exposed to moist air

38. Production of a Gas Carbon Dioxide gas forms when baking soda is mixed with vinegar.

39. Formation of a Precipitate Curds in cottage cheese form when acid is added to milk

40. 4-Chemical Properties and Changes • Physical versus Chemical Changes • DID THE CHEMICAL COMPOSITION CHANGE? • If yes, it’s chemical • If no, it’s physical Change in texture Grinding baking soda into a fine, powdery substance is a physical change Reactivity with Vinegar Gas bubbles are produced when vinegar is poured into baking soda