Volume
Key Concepts
•Volume is a measure of the space occupied by an object.
•The volume of liquids can be determined by placing them in calibrated containers.
•The volume of regularly shaped objects can be directly determined by their dimensions.
•The volume of irregularly-shaped solids can be measured by volume displacement.
Volume is a three-dimensional measurement. A square box that is 1 m in each dimension is 1 cubic meter or 1 m3. On the other hand, a much small square box that is 1 cm in each dimension is 1 cubic centimeter of 1 cm3. The cubic centimeter is a very important unit in the metric system. One cm3 of water is defined in the metric system as 1 gram! We therefore have a direct and simple correlation between mass and volume in the metric system.
While the cubic centimeter (cm3) and cubic meter (m3) are used to report the volume of solids and gases, liquid volumes are reported as milliliters (ml) and liters (l). A milliliter is the liquid volume equal to 1 cm3. In other words, in a 1 cm3 cube of water, we would have 1 ml of water, and that amount of water would have a mass of exactly 1 g. Keeping with the same conventional use of prefixes, a liter contains 1,000 milliliters:
Thus, since we have said that 1 ml of water has a mass of 1 gram, a liter, which contains 1,000 ml of water, has a mass of 1,000 grams or 1 kilogram. Once again, 
we see the simple relationship between mass and volume in the metric system. Consider the simple question, what is the weight of 350 ml of water? The answer is 350 grams, since each ml weighs 1 gram. Consider another simple question: how much do 4 liters of water weigh? The answer is 4 kilograms, since each liter weighs 1 kilogram. Pretty easy.
In the lab, liquid volumes are typically measured by placing them in containers that are calibrated (i.e. have a numbered scale in ml units). Such containers can be made of plastic or glass. A very commonly used instrument to accurately determine the volume of liquids is the graduated cylinder (left).
A liquid is poured into the graduated cylinder and the level at the liquid’s surface is read against the scale printed on the side of the cylinder. Accuracy, approaching a couple ml, is possible with this instrument. Other laboratory glassware, such as beakers and flasks are also typically calibrated as well, but are usually not as accurate as graduated cylinders.
The volume of regularly-shaped solids can be determine directly from their dimensions. Thus, the large box we referred to in a previous section that is, 3 m long, 1.5 m wide, and 2 m high, has a volume of 9 m3. This can easily be calculated using the formula to determine the volume of a rectangle:
Using appropriate formulas, the volume of essentially all regularly-shaped objects can be obtained directly through mathematics. However, the volume of 
irregularly-shaped objects can not be so easily determined, as their dimensions do not conform to a simple mathematical formula. Nonetheless, the volume of irregularly-shaped solids can fairly easily be determined by a process known as volume displacement (below). Using this simple method, a certain volume of water is placed into a graduated cylinder, lets say to the 50 ml mark. Next an irregularly-shaped object (cooper pieces in the video below) is dropped into the cylinder. When examining the new water level, it will be seen to have increased from the 50 ml mark, lets say the 52 ml mark. The volume of the cooper sample is thus 2 ml or 2 cm3.
Key Vocabulary for Volume:
Graduated cylinder: laboratory glassware used to measure volume.
Gram: Basic unit of weight in the metric system. One cubic centimeter of water (1 ml) has a mass of I gram.
Liter: A liquid volume equal to 1,000 ml of water
Milliliter: A measure of liquid volume equal to 1 cm3.
Volume: The amount of space an object occupies, a three dimensional measurement.
Volume displacement: A procedure involving water in a graduated used to determine the volume of an irregularly-shaped solid.
Temperature
Key Concepts
•Temperature is a measure of heat energy.
•The Celsius and Kelvin temperature scales are frequently used in science.
•A thermometer works by expansion of a liquid, sealed in a tube, that’s expansion with increasing heat energy can be observed.
Temperature is a measure of the heat energy (or thermo energy) of a substance. In turn, heat indicates the energy of molecular motion. Thus, the temperature of a substance is a measure of the movement of its component molecules. The more heat an object contains, the more rapidly its molecules move. Thus, the molecules in the solid, liquid, and gas states of a substance would be found to move increasingly fast from solid to gas and the temperature of each would be found to increase correspondingly. The increase in molecular motion caused by heat energy makes most materials expand and increase their volume as their temperatures increase. This is the basis by which typical thermometers work. A material like red-colored alcohol or the metal mercury is sealed in a long, narrow glass tube. As the molecular motion of the alcohol or mercury molecules increases, its total volume increases, and it can be seen to move up the tube in the thermometer. As heat energy is decreased, molecular motion decreases, the substance’s volume decreases, and it can be seen to move down the tube.
What we “read” as temperature is the level at which the fluid in a thermometer attains at a particular amount of heat energy. In order to be able to report precise and reproducible numbers, the length of a thermometer tube must be marked with numbers and calibrated by some standard scale. There are three major temperature scales; Fahrenheit, Celsius, and Kelvin. While the Fahrenheit temperature scale is commonly used in the United States for non-scientific measurements, it is essentially never used in science so we won’t describe it here. Both the Celsius and Kelvin temperature scales are used in science. While the Kelvin scale is very useful, particularly for working at very low temperatures, we will limit our discussion her to the much more familiar Celsius temperature scale.
Using what we know, lets become familiar with temperature by taking a sealed glass tube containing red-colored alcohol and making our own Celsius thermometer. This is actually an Investigation LabLearner eighth graders do to begin the year in the CELL Heat and Heat Transfer.
First, we’ll place the bulb of the tube into finely crushed ice and observe the level the alcohol reaches in the tube and then mark this point with a waterproof marker. We will call the point 0oC, the temperature at which water freezes. Next, we place the tube into a container of water on a burner and watch the column of alcohol rise. When the water begins to boil, we make a second mark on the tube and label it 100oC, the boiling point of water. At this point (see figure below) we could use the thermometer to determine if the temperature of a sample is above, below, or in between the boiling or freezing point of water, but not much more.
To make the thermometer more useful, we will now measure the distance between the two marks we made with a metric ruler (lets say its 15 cm) and divide that number by ten (1.5 cm in this example). This tells us that there are ten equal units of 1.5 cm between 0oC and 100oC on our thermometer. Using the metric ruler again, we mark off the equal divisions between our two starting temperatures (0oC and 100oC) and then number these new marks 10o, 20o, 30o, and so on to 90o, as shown below.
At this point, we can understand why the Celsius temperature scale is sometimes called the “Centigrade” scale. Remember the prefix centi means 1/100. Thus, the centigrade scale is divided into 100 degrees between the freezing and boiling points of water. The centigrade scale was developed by the Swedish astronomer, Anders Celsius, and was named in his honor after his death in 1744.
To determine temperatures above 100oC and below 0oC on our thermometer, we simply need to extend the equal divisions (1.5 cm in our example) above and below these two markings as shown below.
As can be seen, temperatures above 100oC simply continue their upward numbering. At the other end of the scale (below 0oC), however, the numbering becomes negative. Thus, a temperature may be recorded as minus 10 degrees Celsius (-10oC) on a very cold winter day. We immediately know that at such a temperature water will freeze and precipitation, if it occurs, would be in the form of snow.
Finally, to add greater accuracy to our thermometer, we can divide each division of 10 degrees into ten additional equally spaced divisions to represent each individual degree. The portion of our thermometer between 20oC and 30oC is magnified below to see these fine divisions.
Key Vocabulary for Temperature:
Boiling point of water: The temperature at which water changes from a liquid to a gas or water vapor (100C).
Celsius: A temperature scale that sets 0oC as the freezing point of water and 100oC as the boiling point of water and then assigns 100 individual degrees between these two points.
Freezing point of water: The temperature at which water changes from a liquid to a solid (0oC).
Temperature: The amount of heat energy present in a substance.
Thermometer: A scientific instrument that measures temperature (heat energy or thermo energy).
Time
Key Concepts:
•Time is always divided into equal increments.
•Time is measured by clocks and stopwatches in the lab.
•There is no upper or lower limits of time.
One Mississippi, two Mississippi, three Mississippi, four Mississippi. How many off us have used this common method of estimating seconds? This simple, although hardly accurate, process illustrates a most important property of time – it is divided into equal increments.
Time probably presents the greatest conceptual challenge to us. Not in terms of seconds and minutes, but in terms of great lengths of time. Even if we can conceive of the notion that the Earth was formed some 4 billion years ago, we will still likely be stumped by the concept of the “beginning of time” or the “end of time”, or that time is infinite – without an end. Fortunately, to understand science, we can make use of measurable units of time that are much more definable than these more abstract terms.
Although we could begin from any point, let’s start with a year. A year is the amount of time it takes for the Earth to make one complete rotation around the Sun. A year is divided into 365.25 days. Days are, in turn, divided into 24 hours, each of which is divided into 60 equal increments called minutes. Minutes are then divided into 60 equal increments of 60 seconds. Clearly, such numbers as 365.25, 24, and 60 don’t sound like the metric units we have been discussing, which use numbers like 1, 10, 100, 1,000, and so on. However, the metric system does become important in the scientific measurement of temporal units of less than a second. The term millisecond (ms) is equal to 1/1,000 second. Shorter increments of time are represented in the metric system by applying additional prefixes.
We started with the time division of a year – the amount of time required for the Earth to complete one revolution around the Sun. There are many different terms used to group years into longer periods of time, but the year remains the basic unit of time when speaking of time on a large scale. Thus, 10 years is referred to as a decade, 100 years as a century, and 1,000 years as a millennium. However, we still say that some event may have occurred 1,500 or 30,000 years ago.
A common temporal expression when dealing with very long periods of time in the past, the fossil record for example, is the term millions of years ago or mya. Thus, we might speak of a species of reptile becoming extinct 120 mya.
In the laboratory, time is typically measured with a clock or, more frequently, a stopwatch. Even relatively inexpensive stopwatches can fairly accurately measure time down to 1/100 of a second. As anyone who has used a stopwatch has found, at such very short increments of time, human reaction time in starting and stopping the device probably adds to the greatest amount of error in the measurement. As a result, for the accurate measurement of extremely short periods of time, scientists must devise extraordinarily elaborate ways of starting and stopping timepieces to accurately correlate to the event they are timing.
The various increments of time we have discussed are summarized in the Table below.
Key Vocabulary for Time
Millennium: A period of 1,000 years
Millions of Years Ago: mya
Stopwatch: A scientific instrument that measures time in second or even 1/100 second intervals.