Cant Judge A Powder
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| Test Exchange: 2010 |
Contents |
Basic Info
Can't Judge a Powder is a chemistry event. The goal is to teach Science Olympians about the importance of observation of many things in a short period of time. Normally you get 25-35 minutes of using different substance and observe the reaction of the powder that the event coordinator provides.
What You Need to Know
You should have a understanding of different types of reactions ie. chemical and physical. Also know how to use the lab equipment safely.
Observations versus Inferences
Observations versus Inferences An observation is the gathering of information by using our five senses: sight, smell, hearing, taste, and touch. There are two types of observations, qualitative and quantitative. Qualitative observations describe what we observe, such as the sky is blue. Quantitative observations measure what we observe, using numbers, such as the flower has seven petals. Both types of observations are necessary for this event. An inference is an explanation for the observation that you have made. They are based on previous experiences and prior knowledge. While these are important, during a competition you only want to make observations in order to receive the most credit for you answers.
Practice: Label each of the following observation or inference.
- The powder dissolves in water.
- The powder is acidic.
- The powder is soluble in HCl.
- The powder conducts electricity when dissolved in water.
- The pH paper becomes amber when dipped into a solution of the powder.
- The conductivity tester lights up when dipped into a solution of the powder.
Process for Making Observations
This is an event where you are required to make a large number of observations about a sample in a short period of time. The best way to do this effectively is to have a system that you use every time you practice and compete so that you are able to work quickly.
An example of a process is this:
- Start by taking the mass of the powder if you are given a balance.
- Then make observations about all of its physical properties.
- Next move to the distilled water to make observations with.
- Then HCl
- Followed by NaOH.
- Finish with whatever else they have you doing, it could be another solution to test with, or it could be certain experiments that you have to do.
Tips about making Observations
- Make observations, not inferences.
- Write down anything you see, whether it be a color change, or just that the HCl is 1M. The test can technically have questions about anything given to you, so even though making these observations may seem stupid, the more you write down, the more you will have to do the test with.
- Remember that density, conductivity, and pH are all inferences based on something you observe, so write down what you see, not what you infer.
- Control observations are very important and appear on many tests. These can be anything from the amount of a substance given to its color, and are a good way to find out who actually knows what the event is about.
