Change In The State Of Matter-editted

CHANGE IN THE STATE OF MATTER

Teacher’s Guide / Chemistry Form 4 / Spreadsheets SCIENTIFIC CONCEPT There are three physical state states of matter, solid, liquid and gases.

SOLID

LIQUID

GAS

When a solid changes to liquid, there is liquid water. In physical changes, no new substances are produced when the state of a substance changes. A change of state can be reversed as shown in the diagram. Melting

SOLID

Boiling

LIQUID Freezing

GAS Condensation

At the melting point, the solid begins to change to a liquid while at the freezing point; the liquid will form a solid at a constant temperature. Freezing temperature, the temperature at which a substance turns from liquid to solid, and melting temperature, the temperature at which a substance turns from a solid to a liquid, are characteristic physical properties

UNIQUE FEATURE OF ACTIVITY •

This activity requires the student to determine the melting and freezing points of naphthalene. The data can be manipulated easily, for example the temperature of naphthalene will increase during heating with increase in time at regular time intervals, 30 seconds.

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Data displayed in a systematic manner, save time in drawing graphs, show the relationship of different temperatures of naphthalene against time.

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Students will discover that a spreadsheet can be used to process data.

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Allow the students to do more important things such as analyzing the data or the graph.

ENGAGE PHYSICAL STATE OF MATTER

You are given three pictures. Observe the pictures carefully.

QUESTIONS 1. What can you observe from the pictures given? 2. State the phases of every object in the pictures. 3. How they can be formed in different states?

EMPOWER Steps

1. Students are given: •

Thermometer

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Boiling tube

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Tripod stand

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Stopwatch

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Bunsen burner

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Retort stand

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Clamp

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Naphthalene

2. Student need to plan an experiment to determine the melting point and freezing points of naphthalene. 3. Students have to construct a hypothesis for this experiment. 4. Students should know how the melting and freezing points of naphthalene are determined. 5. Helps students to understand the kinetic theory of particles and effect of heat on the kinetic energy of particles. 6. You may give these instructions to start the activity: •

Open a spreadsheet file.

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Name the file as “ the melting point and freezing points of naphthalene”

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Fill the boiling tube with 1/3 naphthalene and place in a water bath as shown in Figure 1.

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Heat the water bath and record the temperature of the naphthalene at regular time intervals of one minute.

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Continue this process until the temperature of naphthalene reaches 90 °C.

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Remove the boiling tube and its contents from the water bath and clamped inside a conical flask.

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Record the temperature at regular intervals of one minute.

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Plot two graph using the data collected.

Figure 1

HOW TO DRAW A GRAPH WITH THE SPREADSHEET 1. a) Highlight cells E5 to F14 for heating curve of naphthalene. b) Highlight cells M5 to N14 for cooling curve of naphthalene. 2. Select a line graph. 3.

In the series box, label series 1 as ‘temperature’

4. Name the chart. 5. Label the x-axis as ‘time (min)’ and y-axis as ‘temperature’ 6. Print out the spreadsheet

RESULT

QUESTIONS

1. Based on your plotted graph, what happen at the temperature at the point C? Explain. 2. As the naphthalene melts, why does the temperature not increase? 3. What happen from point P to R in the graph of cooling curve of naphthalene?

Answers: 1.

At point C, the temperature of the naphthalene begins increase. This is because all the naphthalene has changed from solid to liquid. The heat energy supplied in no longer needed to break the attractive forces between the particles of solid naphthalene.

2.

The temperature is not increase because the heat energy in absorb to break the attractive forces between the molecule. The heat energy has not been used to raise the temperature of the naphthalene.

3.

From point P to Q, the temperature decreases because heat is losing to the surroundings. The temperature decreases to 60°C and remain constant until all the naphthalene has solidified at the point R. This is the solidification or freezing point.

ENHANCE

melts

ANSWERS:

freezes

1. The change of state when solid ice melts to form liquid water is melting and in the reverse process of liquid water change to form solid ice is freezing. 2. During vibrate more and Ice the melting process, the particles in the solid Water more, until they begin to break away from one another. At this point, the solid begins to change to a liquid. For freezing process, the particles movement is slow down even more. Eventually they stop moving, 1. What are the physical changes of matter the picture? except for small vibration whenaccording the liquidtochange to form solid. 2. Give your suggestion on what is happen on the particles of the molecules during this 3. a) Heating curve of water process? 3. Predict the heating curve and cooling curve of the water.

b) Cooling curve of water