Density+Notes

This section is separated by each of our Properties of Matter (POM) lessons. We will add to these as we go through them in class. Notice that the notes are listed in reverse order (most recently studied at the top).

__**POM-5 (Temperature and Density)**__ (This a PowerPoint presentation. Try opening it with PowerPoint.) Our investigative question was - **"What is the effect of thermal energy (heat) on the density of a substance?"**

For Lesson 5 we studied and constructed our own thermometers. While thermometers are a tool to measure TEMPERATURE, **temperature is only a measure of thermal (heat) energy a substances possesses**. (Temperature and heat are NOT the same thing.) We also reviewed from our energy unit that thermal (heat) energy is the speed of molecules of a substance (more thermal energy = faster molecular movement).

In building our thermometers we came to the conclusions that while the mass of the thermometer remained constant (did not change) the volume did. **As temperature (heat) increased the volume increase** (and if the temperature decreased the volume decreased). Reviewing back to POM-2, as the volume of a substance/object increases, the density decreases. **So as temperature (thermal energy) increase the density is decreased** (and as temperature decreases the density increases).

__**POM-4 (Do Gases Have Density?)**__ The main ideas behind this activity is to find **"What is the density of air?"** and **"How can the density of a gas be determined?"**

In Lesson 4 students are challenged to use the skills for measuring mass and volume of liquids and solids (like in POM-2 and 3) and apply them to find the measuring a gas (air). Students learn to use a pump to pull the air molecules out of a rigid plastic bottle producing a VACUUM **(space with no matter/atoms)**. Students then find the mass of air and the volume of the bottle. The calculation of the **density of air** is easy enough (even though many students are surprised to see how **small it is - something around 0.0012 g/cm3**).

__**POM-3 (Predicting Density)**__ Our question was **'How can floating or sinking be accurately predicted?'**

In Lesson 3 we took our density calculations from Lesson 2 and tried to use them to make predictions about the BUOYANCY **(how things sink or float)**. In general, our class found that: - or if the density of the object is less than the liquid it is place in, it will float**.
 * - if the density of the object is higher than the liquid it is placed in, it will sink.

We applied this concept of density by building a density column of three IMMISCIBLE **(liquid that don't mix together)** liquids and 2 solid objects that all had different densities. After allowing the column to settle, we could test out our predictions of sinking and floating finding that **objects/materials with lower density seem to float on top of objects/materials with higher density**.

Our question was **'What is density and how can it be measured?'**
 * __POM-2 (Determining Density)__**

We found that matter can be measured by its MASS **(amount of matter)** or by its VOLUME **(the space it takes up)**. In the lab we used scales and balances to measure the mass and used a graduated cylinder measure the volume. Also, we discussed how we will be using grams (g) as the unit for mass and milliliters (ml) or cubic centimeters (cm3) for volume.

The next part of this activity we wre introduced to the definition and mathematical formula for DENSITY **(the amount of matter in a given space - usually 1cm3) = mass/volume**. We used this formula and our matter measuring skills to determine that the **density of water is 1.0 g/cm3**. This will prove to be important and useful calculation to know. It is also important to realize that **the density number represents the the mass of 1 cm3 of the material**. Using iron for example, which has a density of 7.9 g/cm3. This number tells us that 1 cm3 of iron will weigh (have a mass of) 7.9 grams. The density number means something.

Branching off into the measurement of solids, we practiced measuring and calculating the density of REGULAR objects (ones that have definite height, width and length) like cubes and blocks. Later we found use of Archimede's displacement method of determining the volume of IRREGULAR objects (ones with strange or difficult shapes/dimensions to measure).

__**POM-1 (What is the Matter?)**__ This lab isn't specifically about density, but we are introduced to the term 'Matter' and have 8 different stations in which we see matter differently. As a class we discussed: - how matter can change it's color, shape, size, phase (solid, liquid or gas). - that matter is made up of small particles called 'Atoms'. - how matter is NOT things like energy, thoughts, feelings or other abstract concepts like freedom. - that sometimes matter can mix together, but other times different kinds of matter won't mix. - how matter takes up space and weighs some thing.