Standards of Measurement and SI Units

Why is SI easy to use?

SI is easy to use because it is based on powers of 10

What is SI, and why is it important to the science community?

SI stands for the International System of Units. It is a modified version of the metric system and is the accepted method for measuring by scientist all over the world.

What is a measurement standard and why is it important?

A measurement standard is a quantity that people agree to use as a comparison. Standards are important because they allow measurements to be compared even if different people in different parts of the world take them.

When you want to convert from one metric unit to another what do you have to do?

Multiply or divide by the appropriate power of 10

Why do measurements need to be labeled with a unit?

Without a unit, measurements are just values that have no specific meaning. If you write 6.4 on your paper the reader has no idea what you are talking about: 6.4 students? 6.4 meters? 6.4 apples?

What units are used to indicate a derived volume?

cm3, m3

What is a derived unit? Give an example and explain.

A derived unit is not measured directly but arrived at by combining other units. Volume is a derived unit because you have to measure the length, width, & height and then multiply them together to get the volume

What temp scale is most often used in science? List some temperatures you should know:

Celcius 0˚C=freezing point of water, 100˚C=boiling point of water, 37˚C=normal body temperature, 20-25˚C=normal room temperature

Define density. How could you tell if two balls of the same diameter had different densities? What is the formula for deriving density?

Density is the mass per unit volume. The ball with the higher mass would have the higher density. D = m/v

What is the SI unit for temperature? What is the coldest possible temperature in SI units? What is this temperature often referred to as?

Kelvin, 0K, absolute zero

What units are used to indicated a liquid volume?

L mL

Define Mass. What units and instruments are used to measure mass.

Mass: a measure of the amount of matter in an object units: grams and kilograms equipment: balances

Define temperature. What instrument is used to measure temperature?

Temperature, which is measured using a thermometer, is a measure of how hot or cold something is.

What is the SI unit for length? List the examples the textbook gives as reference to remember a meter, centimeter, and millimeter.

The SI unit for length is meter 1m : baseball bat 1cm: diameter of a shirt button 1mm: 1 tooth along the edge of a stamp

9. Define volume and list 2 units that are used to express volume.

The amount of space something takes up; cm3, m3

What do the prefixes in front of the base unit tell you? Give an example other than the one given in the reading!

The prefix tells you what power of ten to use with the base unit. Example: centimeter, centi= 0.01, so a cm is 1 100th of a meter

What determines what unit to use when measuring?

The size of the object that you need to measure.

What is the SI unit for time?

second