24th Jan 2011

Particulate model of matter

Today, we went through some worksheets on the topic particulate model of matter. I did not type the post for the topic the other time so I will use this post to explain the topic. Since we did some holiday assignment based on this topic, so we had some basic knowledge on this chapter. We also learned some parts of this chapter in Primary School.

Diffusion

The process whereby particles of matter move from one region of higher concentration to a region of lower concentration. e.g. spreading of smells like cooking or perfumes.

The rate if diffusion is based on the temperature. The relative moleculiar mass also affects the diffusion rate.

Kinetic particle theory

Matter is made up of tiny particles that are always in constant motion. The kinetic energy of a particle changes with temperature.

particulate model of matter

Solids:

-Have fixed shapes

-Have fixed volumes

-Cannot be compressed

Liquids:
-Have no fixed shape

-Take the shape of containers

-Have fixed volumes

-Cannot be compressed

Gases:

-Have no fixed shape

-Take the shape of containers

-Have no fixed volume

-Fill up the space of containers

-Can be compressed
Particulate model of matter is used to explain the differences of three states by their difference in their movement and the arrangement of the particles.

Particulate model of solids

The particles in a solid:

-are strongly attracted to one another

-are packed closely together
-are arranged in a fixed, regular pattern

-can only vibrate about their fixed positions

Particulate model of liquids

The particles in a liquid:

-are attracted to one another
-are packed closely together

-not arranged in a fixed, regular pattern

-can move over short distances

Particulate model of gases

The particles in a gas:
-are weakly attracted to one another

-are far apart from one another

-can move freely in any direction

Changes in state of matter

Melting:

When a solid is strongly heated, the particles gain energy and vibrate more vigorously in their fixed positions.When the particles gain enough energy, they break free from each other and move about randomly. Although the particles are no longer held in their fixed positions, they are still close together.

Freezing:

When a liquid is cooled, the particles lose energy and move about more slowly. As the temperature falls, the particles move more slowly until the force of attraction allow them to return to their fixed positions. The substance has changed from a liquid to solid.

Boiling:

When a liquid is heated, the particles gain more energy and move about more vigorously. When the particles have enough energy,they break free from one another. The particles become randomly arranged, spaced far apart and moving at high speeds.

Condensation:

When a gas is cooled, the particles lose energy and they move about less vigorously and at lower speeds. As the temperature falls,the particles lose more energy until they are close enough to be attracted to one another. The substance has changed from a gas to a liquid.

Heating curves(solid-liquid)

-Ice starts to melt at its melting point.

-Temperature remains constant over a period of time.*

-A mixture of solid and liquid exist during the process.

-Temperature will continue to rise once all the ice has changed to water.

Heating curves(liquid-gas)

-Water starts to boil at 100 degrees.

-temperature remains constant.*

-A mixture of liquid and gas exist during the process.

-Temperature will continue to rise as the heating continues.

Cooling curves(liquid-solid)

-The liquid is cooled.

-Temperature drops until the substance reaches its freezing point.

-The liquid freezes into solid state.

-Temperature remains constant**

-A mixture of liquid and solid exist in the process.

*Heat is used to overcome the forces of attraction holding the particles together.

**Heat energy is released as strong attractions are formed between particles to hold them together in a crystal lattice