Tuesday, October 9, 2007
Chemistry Test Advice for Wednesday
I hope that you heed this test-taking advice that has helped thousands of my past students who let me know, even after they go to college, how valuable and practical these tips are.
As you prepare for a test by doing problems and WRITING out and/or DRAWING pictures of explanations, do so exactly as you will be writing on the test; that is, neatly and carefully showing all formulas, units, and calculations with attention to sig figs or labeling all parts of a diagram along with the molecular/particle picture that accompanies the diagram (see notes for examples).
After doing three to five of each type of problem in this unit, the process should become second nature and you will not only get an accurate (true) answer, but also you will reach the answer efficiently because you will see that most of these problems are practically identical.
The key test-taking skill that is consistently ignored by most students (costing them dozens or even hundreds of points per quarter!) involves identifying, labeling, and underlining/circling/highlighting the key terms or data in a question. Once you identify those key terms, you can actually think about what the answer requires. Without knowing what the question asks, you probably will choose a familiar AND true but irrelevant answer.
The data in a quantitative question will always dictate what formula to use so it is mandatory to label the types of data in each question with their respective units. You will find that, in any quantitative question that only one piece of information is missing from the relevant equation and that piece of info is actually what you are solving for!
For example, if the question says that 2458 J of energy were extracted from 654 grams of water at 35.0 degrees C, then what will the final temperature of the water be, then you can see that the energy , q, is given, the mass, m, is given, the substance, water, is given, meaning that you can use the specific heat of liquid water, c, and the initial temperature, Ti, is given.
You are asked for the final temperature, Tf. The only equation that we know of that has those variables is q = mc deltaT.
So, just rearrange , and solve for delta T, which equals q/mc.
Then set delta T = Tf - Ti and solve for Tf.
Done and done! When you take time and care reading and annotating a question, you prevent yourself from making knee-jerk careless mistakes and you also take control of the given problem by identifying what you have and the one thing that you need.
For any endothermic or exothermic problem, DO YOURSELF A BIG FAVOR and DRAW out the situation! If you have a salt-dissolving scenario and the test-tube gets hotter as the salt dissolves, DRAW the arrows of energy going OUT OF the solution TO the glass test-tube and surroundings PROVING to yourself that this is an EXO (out of!) thermic dissolving process (i.e. the surroundings got hotter) typical of a chemical heat pack.
Same deal for melting an ice cube: DRAW the energy arrows going ENDO/into! the ice cube FROM the surroundings in order to melt the ice cube. Since the surroundings LOSE energy, the surroundings will cool, which DOES happen every time that ice melts!
So, abide by these simple yet painstaking tips and watch your test performance improve.
Good luck tomorrow (you won't need it if you have been preparing but I wish it to you just the same).
As you prepare for a test by doing problems and WRITING out and/or DRAWING pictures of explanations, do so exactly as you will be writing on the test; that is, neatly and carefully showing all formulas, units, and calculations with attention to sig figs or labeling all parts of a diagram along with the molecular/particle picture that accompanies the diagram (see notes for examples).
After doing three to five of each type of problem in this unit, the process should become second nature and you will not only get an accurate (true) answer, but also you will reach the answer efficiently because you will see that most of these problems are practically identical.
The key test-taking skill that is consistently ignored by most students (costing them dozens or even hundreds of points per quarter!) involves identifying, labeling, and underlining/circling/highlighting the key terms or data in a question. Once you identify those key terms, you can actually think about what the answer requires. Without knowing what the question asks, you probably will choose a familiar AND true but irrelevant answer.
The data in a quantitative question will always dictate what formula to use so it is mandatory to label the types of data in each question with their respective units. You will find that, in any quantitative question that only one piece of information is missing from the relevant equation and that piece of info is actually what you are solving for!
For example, if the question says that 2458 J of energy were extracted from 654 grams of water at 35.0 degrees C, then what will the final temperature of the water be, then you can see that the energy , q, is given, the mass, m, is given, the substance, water, is given, meaning that you can use the specific heat of liquid water, c, and the initial temperature, Ti, is given.
You are asked for the final temperature, Tf. The only equation that we know of that has those variables is q = mc deltaT.
So, just rearrange , and solve for delta T, which equals q/mc.
Then set delta T = Tf - Ti and solve for Tf.
Done and done! When you take time and care reading and annotating a question, you prevent yourself from making knee-jerk careless mistakes and you also take control of the given problem by identifying what you have and the one thing that you need.
For any endothermic or exothermic problem, DO YOURSELF A BIG FAVOR and DRAW out the situation! If you have a salt-dissolving scenario and the test-tube gets hotter as the salt dissolves, DRAW the arrows of energy going OUT OF the solution TO the glass test-tube and surroundings PROVING to yourself that this is an EXO (out of!) thermic dissolving process (i.e. the surroundings got hotter) typical of a chemical heat pack.
Same deal for melting an ice cube: DRAW the energy arrows going ENDO/into! the ice cube FROM the surroundings in order to melt the ice cube. Since the surroundings LOSE energy, the surroundings will cool, which DOES happen every time that ice melts!
So, abide by these simple yet painstaking tips and watch your test performance improve.
Good luck tomorrow (you won't need it if you have been preparing but I wish it to you just the same).
# posted by C @ 1:30 PM 
