States of matter
A pot of water is placed on the stove. A short while later, it boils as the temperature of the water reaches 100°C and changes from a liquid state to a gaseous state.
If water boils into steam, is it still water, or does it become something new?
If water freezes into ice, is it still water, or does it become something new?
To change liquid water to its solid state, you must cool it to 0°C.
Try This
If you are able, take a can of Pepsi or Coke and a can of diet Pepsi or diet Coke. Drop them into a tub, sink, pool, or lake filled with water. What happens?
- What did the Coke or Pepsi do?
- What did the diet Coke or diet Pepsi do?
- Can you form a hypothesis as to why the two cans behaved the way they did?
Write your observations down in your notebook. You will revisit this activity at the end of this learning activity and use your new learning to help explain them.
Physical Properties
Examining a glass of liquid water, you notice that it is colourless, odourless, tasteless, and liquid at room temperature. All these familiar characteristics—colour, odour, taste, states (boiling and freezing point)—are examples of physical properties. Physical properties can be observed without actually changing the identity of the sample. The following are some examples of types of physical properties.
Physical State
A physical state is the form (solid, liquid, or gas) in which matter exists at various temperatures
Example of states at room temperature
Solid at 20°C: Gold
Liquid at 20°C: Mercury
Gas at 20°C: Helium
Other physical properties
There are other physical properties can be used to describe matter. These don’t require an in-depth explanation. These other physical properties include:
- Colour
- Odour
- Taste
- Shape
- Hardness
Notebook
In your notebook, set up and complete a table like the following:
|
Physical property |
Description |
|---|---|
You now have a good list of physical properties that can be used to describe matter!
Select three of the items from the list below. Using this table, describe the physical properties for each item that you selected.
- Cardboard
- Rubber tires
- Nylon rope
- Steel nail
- Car exhaust
A sample for diamond is given:
|
Physical property |
Description |
|---|---|
|
Hardness |
Diamond is the hardest known natural substance. |
|
Colour |
Diamond is clear. (Sometimes they can be other colours from impurities in the diamond.) |
|
Electrical Conductivity |
Diamond will not conduct electricity. |
|
State |
Diamond is a solid at room temperature. |
Changes of State
There are three states that matter can exist in: solid, liquid, or gas.
Each chemical will typically change from one state of matter to another at a specific temperature.
For example, water will change from a solid to a liquid at 0°C. The reverse process - when water changes from a liquid to a solid - also occurs at 0°C.
Similarly, water will change from a liquid to a gas at 100°C. The reverse process - when water changes from a gas to a liquid - also occurs at 100°C.
The temperatures at which these changes of state occur are also a physical property of matter.
These changes of state are considered to be physical properties because no new chemical is actually made when a chemical changes state. Liquid water, ice, and steam, are all the same chemical - H2O. The chemical can simply exist in different states.
Note: You may have learned in the past that transition between solid and gas is also possible. Please do not worry about this for this course. Most substances do not have a specific temperature at which this transition occurs, and so it will not be used as a physical property that can be used to describe a given chemical.
Chemical Properties
In addition to physical properties, matter can be classified based on its ability to react, which means to change into a new substance with different properties. This is called a chemical property.
Here are some easy-to-test chemical properties:
|
Chemical Property |
Definition |
Example |
|---|---|---|
|
Combustibility |
The ease or difficulty with which a substance burns |
Gasoline is a very combustible substance. |
|
Reactivity with acids |
The ease or difficulty with which a substance reacts with acids |
Baking soda reacts quickly with vinegar, which is an acid. |
|
Reactivity with water |
The ease or difficulty with which a substance reacts with water |
Alkali metals (such as sodium and potassium) react violently with water. |
Try This
Classify each of the following as a physical property or a chemical property.
Qualitative and Quantitative Analysis
Qualitative Analysis
Colourful fireworks displays are possible because someone once observed that certain substances produce certain colours when burned or exposed to a flame. By looking at a fireworks display and knowing the metals that produce certain colours, you can decipher which substances were used in the fireworks display. This type of analysis, in which you compare qualities you observe to a predetermined sample or pattern, is called qualitative analysis. You will be using this technique later in this learning activity to determine the presence of various metals based on the flame colours that are produced once they are heated.
Quantitative Analysis
The other type of analysis is quantitative analysis, which uses techniques that measure the quantity of a particular substance in a sample. Quantitative analysis produces numbers with units such as percentages, grams, litres, and so on. For example, you can use qualitative analysis to determine what substances are present in an unknown sample, and then use quantitative analysis to quantify how much of each substance is found in the sample.
Examples
Consider the physical properties of matter defined earlier and decide if each term would require qualitative or quantitative analysis.
Does determining the state of matter of an object require qualitative or quantitative analysis?
Qualitative. Deciding if an object is a solid, liquid or gas does not require numerical observations
Does measuring the mass of an object require qualitative or quantitative analysis?
Quantitative. Mass is measured using a numerical value.
Does measuring the density of an object require qualitative or quantitative analysis?
Quantitative. Density requires the use of mass and volume, both of which are numerical
Does measuring the solubility of an object require qualitative or quantitative analysis?
Quantitative. Solubility is measured by the mass of solute that can dissolve in a certain volume of solvent. Both mass and volume are numerical measurements.
Does describing the odour of a substance require qualitative or quantitative analysis?
Qualitative. Odour cannot be described using numerical observations.
Earlier in this Learning Activity you were asked to consider how unopened cans of regular pop and diet pop would behave when placed in water. You were also given the opportunity to watch the video "Float or Sink" (Opens in new window)
Can you explain why one can sinks and the other one floats in water?
The regular Coke or Pepsi was denser than the water. The diet Coke or diet Pepsi was less dense than the water and so it floated. The regular soda had a higher density which means that it had a higher mass per volume. This is because of the fact that the regular soda has a lot of sugar dissolved in it, while the diet soda does not. The extra sugar increases the mass of the soda. Both cans had the same volume (amount of liquid) but the regular Coke is made out of a liquid that has a higher mass.
Reflection
Review the learning goals and success criteria for this learning activity. How might you rank your learning at this time? Revisit any areas you are not confident in your understanding.