- Measurements can tell us what is in a substance and how much is there. What else must be true about these measurements?
They must be accurate.
- Several examples were given of measurements that are made on an everyday basis. In what areas were these measurements made?
Gas station, hospital, industry
- What is meant when we say one balance is more ``sensitive'' than another?
It can measure to more decimal places.
- How do we know if an instrument such as a balance is displaying the proper value for the mass of an object?
A standard of known mass is used.
- What is the role of the Bureau of Standards?
They design ways to measure and provide standards.
- Why are human standards (like a former King of England) not desirable?
The standard would vary from king to king.
- What is meant by:
- a titration?
A method for finding the concentration of a solution
- a standard solution?
A solution of known chemical concentration
- When the bay water was tested for salinity, what evidence of chemical change took place?
A milky white solid formed.
- Why is it important to know the amount of pollutants, such as mercury, present in water?
Mercury poisoning can cause neurological disorders or even death.
- What is spectroscopy?
Determining the concentration of a solution from the intensity of its color
- What is meant by precision? Is it possible for measurements to be precise but inaccurate?
When measurements are close to each other; Yes
- Why are repeated trials of the same measurement desirable?
The average value is usually close to the true value.
- Pollutants and trace minerals are often reported in units called ppm. What is a ppm?
Part per million; 1 gram in 1 million grams of material
- Measurements may be made directly and indirectly. Give an example of each that you saw in the video.
Direct - using a balance; indirect - salinity of bay water or measuring for mercury in water