# Effect of Heat on Matter

## Students’ Learning Outcomes

 Investigate the effect of heat on particle motion during a change in states ·         Demonstrate and explain the processes that are involved in the change of states.
·

### Information for Teachers

·         When a solid is heated the vibration movement of its particles increases. At a certain temperature, the solid changes into its liquid. This process is called melting.
·         When a liquid is heated, its particles get more energy and move away from one another. At a certain temperature these particles become independent of one another and the liquid is converted into a gas. This process is called boiling.

### Material / Resources

#### Worm up Activity

·         What happen to ice when it is heated?
(Students response: ice melts)
·         What happens to water if you put it in the freezer?
(Students response: it freezes into ice)
·         Introduce the topic “Effect of Heat on particle motion” and write the topic on the board.

#### Activity 1

·         Draw the following three figures on the writing board or show the chart having the following figures.
·         Ask two students to come forward and arrange the plastic balls in a tray as shown in the figure 1
·         Disturb the arrangement of the balls as shown in the figure 2
·         Spread the plastic balls away from one another as shown in the figure3
Ask the students the following question:
·         Which states of matter are represented by these three figures?
(Students response:  figure 1 represents the regular arrangement of particles in solids.
·         Figure 2 represents the irregular arrangement of particles in liquids.
·         Figure 3 represents the particles of gases. These particles are far apart from each other)
·         Is there a force of attraction present between the particles of a solid?
(Students response: Yes, the particles of a solid attract each other with a strong force of attraction)
·         Are these particles moving?
(Students response:  Yes, the particles are vibrating at a fixed position.
·         What type of movement these particles have in each state?
(Students response: the particles of a child can only vibrate while the particles of a liquid and gas can move in all directions

#### Activity 2

·         Take a piece of ice on a plate and let it melt with the help of a candle.
·                                Inform the students that:
——-Heat has changed the solid ice into liquid water.
——-This process is called melting and temperature at which ice melts is called the melting
point of ice.
——-when a solid is heated, its particles start vibrating faster and attraction between these
particles gets less effective. At a particular temperature, the particles lose their fixed
positions and the arrangement in them goes away and the solid loses its fixed shape.
—– It is converted into its liquid.

#### Activity 3

·         Take water in kettle / beaker heat it so that water starts boiling.
·         Inform the students that:
·         Heat has changed the liquid water into steam (gas)
·         This process is called boiling and the temperature at which a liquid boiles in an open vessel is called its boiling point.
·         When a liquid is heated, its particles start moving at a higher speed. The force of attraction between them becomes less effective.
·         At a particular temperature the force of attraction between these particles gets so infective that they become independent of one another.
·         The liquid is converted into a gas.

#### Activity 4

·         Divide students in groups. Ask each group to pour molten wax on a plate.
·         Ask them what has happened to the wax that is poured on the plate?
(Students responses:  The wax become solid)
·         Why liquid wax is changed into solid wax when poured on the plate?
( Students response: Due to cooling the wax freezes when poured on the plate and becomes soild)
·         Ask them what happen to the particles of a liquid that changes into solid?
(Students ‘ response:  When a liquid loses its energy, its particles start arranging themselves and their movements slow down appreciably.
As a result the liquid freezes and changes into solid. In solid the particles simply vibrate at their fixed positions.
·         Can water also become solid when poured on a plate?  (Students’ response: No)
·         Why not? (students’ reponse: because water needs more cooling than wax.
·         Ask them how can you freeze water to change it into ice? (students’ response: keeping water in the freezez of a refrigerator until water freezes )
·         Explain them that the changing of a liquid into solid is called freezing.
·         Explain them the changes of a liquid them that changing of a liquid them that the changing of a liquid into solid is called freezing.
##### Sum Up / Conclusions
·         A solid can be changed into its liquid form by heating. The process is called melting.
·         A liquid can be changed into its gaseous form by heating. At a particular temperature the vaporization becomes maximum and the liquid starts boiling. This process in known as boil
##### Assessment
Ask the students the following questions:
·         Particles of which state of matter move with the fastest speed? (Students’ response: particles of a gas move with the fastest speed)
·         What makes a solid lose its shape? (students’ response: since the particles of a solid, on heating, lose their fixed positions, so their shape is also lost)
·         Why does a gas not have fixed shape and a fixed volume? (Students’ response:  particles of a gas are moving fast without any significant force of attraction between them.
·         They behave independently and don’t have fixed position. Due to these characteristics gases neither have fixed shape nor a fixed volume)
·         Involve the students in solving the questions given at the end of chapter / unit I textbook.