November 24: Metallic Bonds & Lab Design Review

November 24: Metallic Bonds & Lab Design Review

In class we finished up on metallic bonds, reviewing what we knew and adding a bit more.

A quick question sheet was handed out, referring to: melting points, ductility, malleability and conductivity (questions below).

Questions:

1. Discuss the melting point of Mg (which is 6500oC) with Na (which is 97oC).
2. Explain why Li has a melting point of 180oC, but K has a melting point of 63oC.
3. Describe why Copper allows to be ductile, malleable and a good conductor.

Additional Information:

Alloy Structure Diagram

Steel: is a mixture of Fe and C. Adding Cr makes stainless steel (used in cutlery), in addition adding Ti (and other metals like V) makes titanium steel (used in armour plating and aircrafts).

Brass: is an alloy of Co and Zi (used in taps and musical instruments). Bronze is an alloy of Co and Sn (used in statues). Cupro-nickel is used in 'silver' coins. All of these are corrosion resistant.

We also covered Metallic Characteristics, meaning the set of chemical properties associated with elements that are metals. These chemical properties result from how readily metals lose their electrons. Metallic characters includes the ability to be reduced, formation of ionic chlorides and basic oxides, and the ability to displace hydrogen from dilute acids.



Relating to metallic characteristics, we covered trends and influences for certain switches between metals and non-metals. 

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Lab Design Review:

In class as well as going over metallic bonds, we also used class to go through the IB1 Chemistry Analysis and Evaluation rubric. We covered systematic errors, conclusions and data.

Systematic Erros:

1. Folding of filter paper/surface area
2. Time
3. Wind draft
4. Room temp.
5. length of run/scales
6. Elastic band coverage

Conclusion:

To understand the conclusion and receive full marks you need to understand the differences between: interpreted conclusion, the actual conclusion and the contextual conclusion. The main difference is what you make your conclusion upon. For example the interpreted conclusion should be done on your general data, where as the actual conclusion should focus on processed data. Finally the Contextual conclusion should be according to the theory of the experiment.

Data:

For the data recordings, the main emphasis was placed on "keeping units and uncertainties" correct and according to their relevant points of interest.

Also you shouldn't forget to include qualitative and quantitative observations.

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