Teacher Slide

1. Teacher Slide • Have oil, corn syrup, and water to demonstrate different viscosities. • Have burner turned on low. Heat oil & corn syrup so that you can show how viscosity changes with temperature. • Clay and crackers to illustrate malleability v. brittle.

2. Mixtures Homogeneous Heterogeneous Bell work • 9/9/09 Q: Fill out this concept map and define the terms in the bottom three circles:

3. Section 2: Properties of Matter • Objectives • List examples of physical properties • Understand the usefulness of knowing physical properties • Identify processes to separate mixtures • Identify when physical changes occur

4. Vocabulary • Physical property • Viscosity • Conductivity • Malleability • Melting point • Boiling point • Filtration • Distillation • Physical change

5. Examples of Physical Properties • We learned to characterize matter based upon uniformity of composition. • We’ll now learn to categorize matter based upon its physical properties. • Physical Property: any characteristic of a material that can be observed without changing the composition of the substance

6. Examples of Physical Properties • Substances all around can be identified by many features. • They can be categorized by these features such as their color, taste, how they feel, their temperature • These are basic examples of physical properties that can be observed or measured. • There are many more examples which this section will cover.

7. Why Does it Matter? • If you were given a sample of water how could you determine if it was pure or not? • By taste? • Let’s say it’s salty. • Salt isn’t going to kill you but what if there were a tasteless, colorless, odorless poison, such as Botulinum toxin, in the sample. • You wouldn’t want to taste the sample then would you? • The point is that water, salt, and toxins all have physical properties, that if known, can help you determine what substance is what.

8. Examples of Physical Properties • Some of the more relevant physical properties in chemistry are: • Viscosity • Conductivity • Malleability • Hardness • Melting and boiling points • And density • But there are others. • This section is dedicated to surveying the physical properties of matter.

9. Examples of Physical Properties • Viscosity: the tendency of a liquid to keep from flowing… to resist flowing. • Take for instance, bottles of honey (or syrup) and vinegar. • Which flows faster? • If you were to pour out these bottles the vinegar would flow out much faster than the honey. • Viscosity describes how a fluid flows, more specifically how slow it flows compared to another fluid.

10. Viscosity • How do you describe viscosity? • As with most physical properties, the method is based upon the comparison between different samples. • The one that flows slower has higher viscosity.

11. Viscosity • Consider driving in Arizona compared to driving in Minnesota. • You would want to choose you motor oil depending on the temperatures outside. • Too viscous and the oil may not flow in cold temps. • Too thin and engine damage could occur.

12. Viscosity • Viscosity can be important considering many substances, such as oil. • Its resistance to flowing helps lubricate engine parts. • Viscosity can change with temperature. • So if you hear up oil it pours faster.

13. Viscosity v. Temperature • Examine the graph and tell me how does viscosity change with temperature?

14. Examples of Physical Properties • Conductivity: the ability to allow heat to flow • Materials are categorized by conductivity for many important reasons. • These come into play in everyday life and in industry as well • Conductors have high conductivity • They allow heat, and usually electricity, to flow very rapidly. • Insulators generally have poor conductivity • For example wood. Electricity and heat flow very slowly if at all throw the material. • Glass is also another insulator. • Inert gasses (such as argon) are others.

15. Materials for windows are chosen to reduce conductivity of heat between the inside and outside of homes. • The glass has low conductivity. • The “GAS FILL” is a noble gas, something like argon, which does not conduct heat.

16. Conductivity • When you cook what type of utensil do you use? • What happens when you use a metal spoon? • If conductivity is the ability of heat to flow what material is the most conductive? • A wooden spoon? • A metal spoon? • A plastic (nylon) spoon?

17. Examples of Physical Properties • Malleability: the ability to be hammered or pressed without shattering. • Materials that are malleable: • Metal • Clay • Wax

18. Malleability • Clay and wax are chosen for molds and sculptures because they can be shaped without them crumbling or shattering.

19. Other Examples of Physical Properties • Ductility: The ability to be permanently deformed; such as bent, stretched, warped, or drawn into wires. • A lot like malleability. • Usually metals, like copper, gold, zinc, steel. • The opposite of malleable & ductility is brittle. • Glass • Wood • Crackers

20. Examples of Physical Properties • Hardness is a relative description based upon observing which material can scratch the other. • Hardness is usually used as a comparison between two materials. • Such as diamonds are harder than glass.

21. Hardness • Tools for wood carving are chosen because they are harder than wood.

23. Other Examples of Physical Properties • Luster: a sheen or soft glow generated from a reflective surface. • Luster is often discovered when a material is polished. • Luster can come in a lot of forms. • The opposite would be matte or dull.

24. Examples of Physical Properties • Phase Changes • When a substance changes its state it is a physical property of the substance. • Example: When water boils some of the water molecules turn to a gas that rises to the top. • Example: When dry ice (solid carbon dioxide) changes to a gas it still remains carbon dioxide…it’s just the gas version. • When a substance changes state is an important physical property.

25. Examples of Physical Properties • Melting point: the temperature at which a substance changes from a solid to a liquid • Water “melts” from ice to water at around 33°F or 1°C • Boiling point: the temperature at which a substance boils, or changes from a liquid to a gas • Water boils at 212°F or 100°C

26. Examples of Physical PropertiesMelting and boiling points (pg 47) What do you notice about the units being used?

27. Quick Check Point. 1 minutes… Building Vocabulary • The temperature at which a substance changes from a solid to liquid. • the ability to allow heat to flow • The tendency of a liquid to resist flowing • The ability of a solid to be hammered without shattering • a sheen or soft glow generated from a reflective surface.

28. Examples of Physical Properties • Density: Ratio of the mass of a substance to its volume • It can be a valuable test to check for a substance purity or useful physical property for choosing a substance for a particular job. • Precious metals, fuels, chemicals are all examples of substances that are checked for purity by calculating their densities. • What is the equation for calculating density? • Density = mass/volume

29. Using Physical Properties • Physical properties are used for several purposes: • To identify a material • To choose a material for a specific purpose • To separate substances in a mixture

30. Using physical properties • Using properties to ID materials • This can lead to discoveries of unknowns • The process: • First identify the properties to test. • Do you want to calculate density, melting point, boiling point, conductivity? • Next test the sample. • Then compare the findings with known materials. • Use what’s already known to compare with your sample.

31. Melting and Boiling Points • Melting and boiling points are used all the time for very important reasons. • These physical properties allow substances to be separated by boiling point are to be chosen for particular uses. • Such as adding salt to water in increase the boiling point, which speeds up cooking times. • Such as metals are chosen to cook with because they conduct heat, but have very high melting points.

32. Density • Densities for all pure substances are known and can be found searching the internet. • If you have an unknown sample, how do you think that being able to calculate density could help determine it’s purity? • If something has impurities it would have variable mass and different densities.

33. Using physical properties • Using properties to choose materials • The properties of a substance determine which materials are used in specific ways • Choosing between materials based on their properties ensures effective products

34. Using physical properties • Read and annotate physical properties on the hand out given. • Discuss these questions with your group. • What are some physical properties of clay? Of the metal? Of the wax? • Which is more malleable? What are the different melting points (which is highest/lowest)? • Describe this process for making a sculpture? • Why is it important that wax has a lower melting point than clay?

35. Using properties to separate mixtures • The physical properties of a substance can be used for a variety of reasons, one being deciding what to use for a specific task. • Another use for knowing physical properties is purification, or isolating one specific substance from a mixture. • Two methods of separating substances from one another based upon physical properties are: • By filtration • And by distillation

36. Using properties to separate mixtures • Filtration: Is the process that separates materials based upon the size of their particles • Filters are chosen depending on the materials that are wanted OUT of the mixture • Range from strainers and sifts to filter paper and substances even more fine • Filters can be physical (such as a collander or coffee filter) or chemical (such as in DNA purification).

37. Choose the best filter for the job. • If you need to drain water from spaghetti. • If you want to filter the flavor out of ground coffee beans. • If you want to find bones in dirt.

38. Using properties to separate mixtures • Distillation: The process that separates substances in a solution based upon their boiling points. • Every substance has a unique boiling point. • With this fact, mixtures can be heated to boil out substances in solution. • Ex: purification of sea water.

39. Sea water in Purified water out

40. How Can This Help You? • Imagine you are stranded without drinking water. • What scientific technique could you use to purify a water source? • Distillation • Solar Still

41. Recognizing physical change • Physical change: occurs when some of the properties of a material change, but the composition of substances in the material remain the same • Some ways can be reversed • Such as melting and freezing • Example: Regardless of its state, either as ice or liquid or gas, water is always hydrogen and oxygen • Some can’t • Like cutting and slicing • Example: Getting your hair cut.

42. Summary • Physical properties include viscosity, conductivity, malleability, hardness, melting and boiling points, and density • Knowing physical properties allow us to identify a material, to choose a material for a specific purpose, and to separate substances in a mixture • Processes to separate mixtures include filtration and distillation • Physical changes occurs when some of the properties of the material change but the substances remain the same.

43. Study Hint: Physical Properties Cluster • Name 8 physical properties and describe the features of this property in the correct box. • Choose an example that demonstrates this property.

44. Comparing Viscosities 11 • Observe these samples. • Which of these samples has higher viscosity?