Home PHYSICS TOPIC 6: STRUCTURE AND PROPERTIES OF MATTER | PHYSICS FORM 1

# TOPIC 6: STRUCTURE AND PROPERTIES OF MATTER | PHYSICS FORM 1

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## TOPIC 6: STRUCTURE AND PROPERTIES OF MATTER | PHYSICS FORM 1

### Matter

Is anything that has mass and occupies space.

#### State of Matter

State of matter is defined in terms of the phase transitions which indicate the change in structure and properties.

Matter exists in three physical states, namely

– Solid state

– Liquid state

– Gas (Vapor) state

#### Structure of matter

Matter is made up of tiny particles.

The particles are either atoms or molecules

#### Atom

Is the smallest particle of an element, which can take part in a chemical reaction.

For example, Sodium atom (Na), hydrogen atom (H) etc

#### Molecules

A molecule is a group of two or more atoms held together by chemical bonds.

For example, water molecule (H2O), hydrogen molecules (H2)

#### Particulate Nature of matter

Matter is made up of millions of tiny particles which cannot be seen with naked eyes

These particles are called atoms and are made up of sub – atomic particles called protons, neutrons and electrons

Atoms join together to form molecules

The figures below show the atoms in solid , liquid and gas respectively

#### Kinetic theory of matter (molecular theory of matter)

The kinetic theory of matter describes the physical properties of matter in terms of the behavior of its component atoms or molecules

It states that: “All matter is made up of very small particles that are in constant motion”

The more heat energy the particles possess the faster they move

In a solid, the particles are arranged close together in a regular pattern and vibrate in fixed positions hence possess lowest kinetic energy

In a liquid, the particles are still close together but in an irregular arrangement. Particles in a liquid move about and are able to slide past one another

In gas, the particles are far apart, moving rapidly and bouncing off the wall of the container

#### The table below summarize the properties of these states of matter

 Properties of three states of matter Solid Liquid Gas Particles are closely packed together Particles are slightly further apart Particles are further apart Has definite shape and volume Takes the shape of the container holding it .has definite volume Has neither definite shape nor volume Has strongest inter- molecular forces Inter-molecular forces are moderately strong Has weak inter – molecular forces Particles are not free to move. They just vibrate in a fixed positions instead Particles move with a moderate speed Particles move randomly with a high speed Has low kinetic energy Moderate kinetic energy, enough to ‘stretch’ the intermolecular forces High kinetic energy enough to break all inter – molecular forces

### The concept of Brownian movement

Brownian movement is the irregular motion of tiny particles suspended in a fluid (fluid or gas)

Robert Brownian, an English Botanist discovered that, the random motion of the pollen grains in water was caused by the collisions between them and the molecules of water

This motion is called Brownian movement (motion)

#### Molecular properties of matter include the following;

1. Elasticity

3. Surface tension

4. Capillarity

5. Osmosis

6. Diffusion

#### 1. Elasticity

Is the ability of a body to return to its original shape and size after deformation.

OR

Is the ability of a body to resist any permanent change to it when stress is applied

A body with the ability to undergo elasticity is called Elastic material.Eg spring

Materials are elastic to some degree until elastic limit is reached

A material which does not undergo elastic deformation is called Brittle material. For example, glass, block etc

When material deformed beyond the elastic limit it becomes plastic, means it will not regain its original shape even though it does not break. This type of deformation is called PLASTIC DEFORMATION

A Material which does not return to its original shape and size after deformation is called INELASTIC or PLASTIC material. E.g plastic bags, plastic utensils etc

Relationship between tension and extension of a loaded elastic material

This can be explained in Hooke’s law which states that:

“Within the elastic limit, the extension is directly proportional to the force applied”

OR

“Provided that the elastic limit of a body is not exceeded, the extension is directly proportional to the force applied”

Tension can be described as the force (F) transmitted within a string or rope or wire when it is stretched or elongated

Extension (e) is an excess length obtained after stretching a wire (rope or string)

Hooke’s law describes that when a force is applied to a material, the length of the material will keeps increasing in the same proportion as the force

If the limit of extension (elastic limit) is not reached, the material can return to its original shape and size after removing the applied force

But when the elastic limit is reached then the body will not return to its original shape and size even after the removal of the force applied

Mathematically Hooke’s law can be expressed as:

#### The SI unit of k is Newton per metre (N/m)

The area under the graph of proportionality of Load against extension gives the work done in stretching a spring, see the figure below

Therefore And the work done in stretching the spring is given by

The relationship between tension and extension of a loaded elastic material

can also be explained using the following graph

The graph of Tension against extension

.

Interpretation of the graph

Between point O and A (O – A)

The tension is direct proportional to extension. This was discovered by Hooke and finally he came with a law which called Hooke’s law.

At this stage, the body can regain its original shape and size if tension is removed

At point A

Point A is called the limit of proportionality or elastic limit

Between point A and B (A – B)

This is called the region of elastic. In this region a small force produces a large extension which is not directly proportional to the extension

Between point B and C (B – C)

This is known as the region of plastic deformation. At this region material will not return to its original shape and size when applied force (tension/load) is removed

Beyond point C

Beyond this point the body becomes thinner and ultimately break due to excessive application of force

#### Application of elasticity

##### At homes is applied in.

– Rubber gaskets that seal the refrigerator door

– Clothing

– Springs in furniture

– Rubber bands that holds things together

– Toys like balloons and balls

##### In transportation, elasticity may be applied in:

– Rubber tyres, hoses, belt and shock absorbing springs for car and trucks

– Aeroplane wings

– Supporting cables for bridges

##### In Industry, elasticity is applied in:

– Conveyor belts

– Measuring weight

– Steel beams used in constructions

– Insulation of vibration and sound

### Surface Tension

Is the ability of a liquid surface to behave like a fully stretched elastic skin.

OR

Is a force present within the surface layer of a liquid that causes the layer to behave as an elastic sheet.

#### Causes of surface tension

Surface tension is the result of inter – molecular cohesive bonding among the molecules of a liquid.

(Surface tension occurs due to the force of attraction between molecules of a liquid)

#### Application of surface tension (Examples of surface tension)

– Walking of pond skater on the surface of water

– Floating of a needle on the surface of water

– Mosquito eggs can float on water because of its surface tension

– Soaps and detergents lowering the surface tension during washing of clothes

– Surface tension prevents water from passing through the pores of an umbrella

– Warm water is used for washing purpose as heating increases the surface area and reduces surface tension

– Antiseptics like Dettol have low surface tension, so that they spread faster

– Toothpaste contains soap, which reduces the surface tension and helps it spread freely in the mouth

– Hot soup has a lower surface tension than cold soup, hence hot soup is tastier than cold soup.

### Factors affecting Surface Tension

1. Nature of the liquid

Different liquids have different surface tension, for example, mercury has higher surface tension than water

2. Contamination (impurities)

Impurities in a liquid lower the surface tension. The substance which lowers surface tension is called SURFACTANTS (acronym for surface active agent). Example of surfactants is detergents

3. Temperature

Surface tension of a liquid decreases with increase in temperature

### Intermolecular Force

Is the force of attraction or repulsion between particles of matter (atoms/ molecules)

Cohesive force

#### Cohesion

Is the force of attraction between the molecules of the same substance.

For example, water and water molecules

Definite shapes of a solid are due to strong cohesion force among its molecules

Is the force of attraction between the molecules of different substances.

For example, water to glass molecules

#### Effect of Adhesion and Cohesion

Mercury forms convex (downward) meniscus because it possesses strong cohesive force than adhesive force

Water forms concave (upward) meniscus because it possess strong adhesive force than cohesive force

Drop of water on the surface of some leaves is perfect sphere due to strong cohesive force than adhesive force

Drop of mercury on the surface of different material is perfect sphere due to strong cohesive force than adhesive force

Water spread over a glass because it possess strong adhesive force than cohesive force

#### Application of Adhesive and Cohesive force

Adhesion is used to stick two different objects together. E.g using glue or tape

Adhesion is used to remove harmful materials from drinking water e.g bacteria

The bodies of Plants and animals use the cohesion of tissue to repair damage

Ink sticks on paper because of adhesive force between the paper and ink

Cohesion assists in transport of water in plants and animals by allowing one molecule to pull others along with it (While Adhesion occurs when the water molecules cling to the xylem tissue)

#### Capillarity (Capillary action)

Is the ability of liquid to rise or fall in a narrow tube.

OR

Is the tendency of a liquid to rise in a narrow tube or to be drawn into small openings

OR

Is the ability of a liquid to flow against gravity in a narrow space (thin tube)

When you dip a capillary tube in water, the water rises due to greater adhesive force

When you dip a capillary tube in mercury, the mercury falls due to greater cohesive force

The greater adhesive and cohesive force, the greater the capillary action

#### Application of Capillarity

1. The raising of oil in the wicks of lamps in the cotton threads

2. The absorption of water by a towel (paper or cloth)

3. Water rises in the soil because the soil is composed of fine particles

4. It facilitates the transport of water and nutrients from the roots

5. Ink rises into the blotting paper through those fine pores

6. It Promotes the movement of ground water

7. Cotton clothing in hot climates uses capillarity action to draw perspiration away from the body

### Osmosis

Is the movement of a solvent from a region of low concentration to a region of high concentration through a semi-permeable membrane.

Consider the experiment below

Peal a potato

Keep over salts

The potato shrinks due to movement of water from potato (low concentration) to salt (high concentration)

#### Application of Osmosis

Removal of harmful ingredients from drinking water

Controls the movement of water and nutrients in and out of the cell

Removing salt from seawater so as to make it suitable for drinking and other domestic uses

Absorption of water molecules from soil to plant

Aquatic life is controlled by osmosis

Filtration processes

#### Diffusion

Is the movement of particles from a region of high concentration to one of low concentration.

For example, spraying of a perfume

#### Application of Diffusion

Detecting harmful substance in the environment

In the use of refreshers and other sprays

Respiration process, oxygen diffuses into blood stream

Balance concentration of water and nutrients in and out of the cells of living organisms.

### Assignment

1. Define the term matter. With examples, List down the states of matter.

2. State the difference between a solid, a liquid and a gas

3. What is Brownian movement?

4. Differentiate between cohesion and adhesion

5. State the kinetic theory of matter

6. State Hooke’s law and identify the application of elasticity in everyday

7. A certain spring has a force constant of k = 25 N/cm.

a) If an object with a mass of 500 g were hung from the spring, how far in centimeters, would it stretch?

b) What is the mass of an object that stretches the spring 35 cm?

8. The length of a spring is 16.0 cm. Its length becomes 20.0 cm when supporting a weight of 5.0 N. Calculate the length of the spring when supporting a weight of 6.0 N (ANS: L = 16.0 + 4.8 = 20.8 cm)

9. What is surface tension and discuss four application of surface tension 10.What is elasticity

10. What is the essential of kinetic theory of matter?

12. Differentiate between plastic and elastic materials

13. What is elastic limit?

14. A force of 7.5 N stretches a certain spring by 5 cm. How much work is done in stretching this spring by 8.0 cm? (ANS: W = 0.48 J)

15. What are the uses of capillary action in everyday life

16. Sketch the graph showing how force applied in a stretched string varies with its extension

17. State Hooke’s law. A scale pan of weight 0.4 N was attached on a spring balance and produced an extension of 24 mm when a load of 2 N was placed on it. Calculate the load on the scale pan when the extension is 16 mm.

18. Differentiate between Osmosis and Diffusion

19. Match the items in list A with the items in List B

 List A List B a) Surface tension b) Elasticity c Diffusion d Osmosis e) Capillarity f) Adhesion g) Cohesion i) The ability of a body to regain its shape and size after deformation ii) Movement of particles from the region of high concentration to one of low concentration iii) Is the ability of a liquid to flow against gravity in a narrow space iv) Is the ability of the surface of a liquid to behave like a fully stretched elastic skin v) Is the force of attraction between the molecules of the same substance. vi) Is the force of attraction between the molecules of different substances vii) Movement of solvent from a region of low concentration to one of high concentration through semi permeable membrane