Measurement

Metric System System of measurement based on the number 10 SI – The International System of Units Common SI prefixes: Kilo- (k) means 1,000 Hecto- (h) means 100 Deka- (da) means 10 Deci- (d) means 0.1 (one tenth) Centi- (c) means 0.01 (one hundredth) Milli- (m) means 0.001 (one thousandth)

Length The basic unit of length in the SI system is the meter. To measure objects smaller than a meter scientists use the centimeter (cm) or the millimeter (mm) 100 cm = 1 meter 1000 mm = 1 meter For larger measurements, scientists use kilometers. 1000 m = 1 km

Mass Mass is the measure of the amount of matter an object contains The basic unit of mass in the SI system is the kilogram (kg). The kilogram is useful in measuring the mass of bicycles, cars, or people. To measure the mass of smaller objects you will use a unit known as the gram (g) There are 1,000 grams in a kilogram.

Measuring Mass To find the mass of an object you may use a digital balance.

The Difference Between Mass and Weight Weight is a measure of the force of gravity acting on an object. You can measure weight by using a scale. When you stand on a scale gravity pulls you downward. However, if you weighed yourself on the moon you would weigh much less. Mass is a measure of how much matter an object contains so it remains constant no matter where an object may be. Your mass is the same on the moon as it is on Earth.

Volume of Liquids Volume is the amount of space an object takes up. To measure the volume of a liquid, scientists use a unit known as the liter (L). You can measure smaller liquid volumes in milliliters (mL) 1,000 mL = 1 L

Graduated Cylinder

Graduated Cylinder Scientists commonly use a graduated cylinder to measure liquid volumes. The graduated cylinder is marked off in milliliter segments. When liquid is poured into a graduated cylinder, the top surface of the water is curved. This curve is called the meniscus. To determine the volume of the water, you should read the bottom of the meniscus

Volume of Rectangular Solids The unit to measure the volume of a solid object is a cubic centimeter (cm³) A cubic centimeter is equal to the volume of a cube that measures one centimeter on each side. 1 cm³ = 1 mL For solids with larger volumes, scientists use the SI unit known as the cubic meter (m³). A cubic meter measures one meter on each side.

Formula for Volume Volume = length x width x height

Volume of Irregular Solids If you wanted to find the volume of an object that you could not determine the length, width, and height (example: rock), you would immerse the object in water and see how much the water level rises. You would subtract the amount of water that you started with from the amount of water that the object forced the water to rise to and you would know the volume of your object.

Density Density is a measure of how much mass is contained in a given volume. To calculate density you divide the mass by the volume: Density = Mass Volume

Because density is actually made up of two different measurements – mass and volume - an object’s density is expressed in two units. Two common units of density are grams per cubic centimeter (g/cm³) and grams per milliliter (g/mL) The numerator is the measure of mass while the denominator is the measure of volume

Densities of Common Substances Substance Density (g/cm³) Air 0.001 Ice 0.9 Water 1.0 Aluminum 2.7 Gold 19.3 The density of an object stays the same no matter how large or small a sample of the substance is.

An object will float if it is less dense than the surrounding liquid. A piece of wood with the density of 0.8g/cm³ will float in water because the density of water is 1.0 g/cm³ An object will sink if it is more dense than the surrounding liquid. A ring made of pure silver with a density of 10.5 g/cm³ will sink in water because silver is more dense than water.

Time The second (s) is the SI unit used to measure time. Clocks and watches are used to measure time Common Conversions for Time 1s = 1,000 ms (milliseconds) 1 min = 60 s 1 h = 60 min

Temperature Scientists commonly use the Celsius temperature scale. On the Celsius scale water freezes at 0°C and boils at 100°C. Normal human body temperature is 37°C. In addition to the Celsius scale, scientists sometimes use the Kelvin scale. The kelvin (K) is the official SI unit for temperature

Zero on the Kelvin scale is considered the coldest possible temperature (this is called absolute zero). Absolute zero on the Celsius scale is -273°C. The Kelvin scale is useful because it does not have negative numbers to complicate calculations. You can measure temperature by using the thermometer. Place the thermometer in a substance and wait for the liquid in the thermometer to stop moving. Then read the number next to the top of the liquid in the thermometer.