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18 Dec 2019

Metallic solids are solids composed of metal atoms that are held together by metallic bonds. They also tend to be good conductors because...

the electrons in metallic solids are tightly bound allowing other electrons to flow freely.

metals are malleable and can be pounded into sheets.

metals are ductile and can be pulled into wires.

the electrons in metallic solids are delocalized.

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64. Which of these statements about fatty acids are false? A. The physical state of a triglyceride with three unsaturated fatty acid tails would be a clear liquid. B. Complex lipids that contain mainly unsaturated fatty acids are liquids (oils) at room temperature C. Its best to use fats with high melting points in our diet. D. A disadvantage of the ability of saturated fats to pack tightly is that tightly packed, saturated fats clog arteries as atherosclerosis 65. Trans fatty acids A. are formed when vegetable oil is hydrogenated (for solidification). B. are found in fried foods C. have an atypical shape that affects their chemical activity D. are not flexible and can adhere to surfaces E. should be avoided because they are composed of partially hydrogenated (partially hardened) oils F. are all of the above 66 Which of these statements about fatty acids are false? A. When plants and animals build fatty acids they make the trans forms. B. Food manufacturers found that foods like chips with the trans form have a longer "shelf life" C Natural cis fatty acids tend to turn rancid and spoil D Although natural cis fatty acids turn rancid and spoil, it is the cis form that is used by the body. E.The process of hydrogenation, in which hydrogens are added to unsaturated fats, produces a mixture of saturated fatty acids and standard and trans forms of unsaturated fatty acids 67. Good tips for reducing dietary fats are to A. use non-fat or low-fat dairy products and other products B use low-fat cooking methods C bake, roast, steam, broil, stir fry, microwave D. seldom have fried foods E choose lean cuts of meat, trim fat F. do all the above 68. Which of these statements about the properties of fatty acids are true? A. Melting point of all fatty acids increases with increasing hydrocarbon chain length (i.e increasing size) B cis double bonds prevent good alignment of molecules in unsaturated fatty acids leading to C Melting point of unsaturated fatty acid are lower than that of a saturated fatty acid with the D. The melting point of a saturated fatty acid is greater than that of an unsaturated fatty acid of poor packing same number of carbon atoms due to the presence of their double bonds the same chain length, because saturated fatty acid chains tend to be fully extended and to stack in a regular structure, thereby causing increased intermolecular attraction. E. all of the above 69. Freebie 70 Freebie

Chemistry 162 Lab Activity

Introduction Water has an amazing ability to adhere (stick) toitself and to other substances. Hydrogen bonds form when hydrogenatoms covalently bonded to nitrogen (N), oxygen (O), or fluorine(F) in the form of covalent compounds such as ammonia (NH3), water(H2O) and hydrogen fluoride gas (HF). In these molecules, thehydrogen atoms do not pull as strongly on the shared electrons asthe N, O, or F atoms. Therefore, the molecules are polar; thehydrogen atoms become positively charged and are able to formhydrogen bonds to negative ions or negatively charged parts ofother molecules (such as the N, O, and F atoms that becomenegatively charged in these compounds). Hydrogen bonds are not truebonds like covalent bonds or ionic bonds. Hydrogen bonds areattractions of electrostatic force caused by the difference incharge between slightly positive hydrogen ions and other, slightlynegative ions. These attractions are much weaker than true ionic orcovalent bonds, but they are strong enough to result in someinteresting properties.

In the case of water, hydrogen bonds form between neighboringhydrogen and oxygen atoms of adjacent water molecules. Theattraction between individual water molecules creates a bond knownas a hydrogen bond (Fig. 1).
Fig. 1: Hydrogen bonds shown as the dotted lines between watermolecules.
Cohesion Molecules of pure substances are attracted to themselves.This sticking together of like substances is called cohesion.Depending on how attracted molecules of the same substance are toone another, the substance will be more or less cohesive. Hydrogenbonds cause water to be exceptionally attracted to each other.Therefore, water is very cohesive.
Adhesion Adhesion is similar to cohesion, but it involves unlike(i.e. different) substances sticking together. Water is veryadhesive; it sticks well to a variety of different substances.Water sticks to other things for the same reason it sticks toitself â because it is polar so it is attracted to substances thathave charges. In this lab activity, you will be asked to use thematerials and procedures provided to explore the properties ofwater that involve both cohesion and adhesion. Be sure to writedown your observations and results as you progress. sults as youprogress.

Fig. 1

Hydrogen bonds shown as the dotted

lines between water molecules.

Part 1:

Exploring Water

Procedure

How many drops of water can you fit on the surface of a pennywithout the water spilling over?

Predict how many drops of water will fit on a penny. Record yourprediction.

Use the plastic pipette to drop water on the surface of a penny.Drop car

efully and slowly to fit as

many drops as possible on the penny. Count each drop until thewater spills over the side of the

penny and record your results.

Compare your results to those of your classmates. Record therange and calculate the average

number

of drops that fit on a penny.

Add more drops to the penny, without letting the water spillover. Carefully observe and draw the

water on the penny.

Record

a hypothesis for the behavior of water that you observed, usingthe language of cohesion

and adhesion

in relation to the water and the penny.

Record your results and

thinking in your notebook.

Can you

disturb

the water on the penny without spilling it?

dd drops of water to the penny, until the water is almost readyto spill over.

Predict what will

happen when you insert a toothpick into the surface of the waterpiled on the

penny. Record your prediction.

Insert the

toothpick

and carefully observe the surface of the water.

Try inserting the

toothpick

in various ways. Observe the surface of the water.

Pay special attention to

the water surface where the skewer enters the water.

Record your observations and draw what you see.

Repeat

these

procedures using a paper clip and the metal clip part of abinder clip. Try to indent the

pile of water as much as p

ossible without spilling it.

Record your observations and dra

w what you see, paying careful

attention to the surface of the

water.

Record

a hypothesis for the behavior of water that you observed usingthe language of cohesion

and adhesion in relation to the

toothpick

, the paperclip, the binder clip, and the water.

Record your results and

thinking in your notebook.would you please answer the questionfor me . Thanks

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