MATTER, ATOMIC STRUCTURE, STATES OF MATTER, DIFFUSION, OSMOSIS, BROWNIAN MOTION

CONTENT

• Atomic Structure
• Molecular Theory of Matter
• Diffusion and Osmosis

MATTER

Matter is defined as anything that has mass and occupies space. All substances are made up of matter. It exists in three states namely, solid liquid and gas. Examples of solids are ice, brick, metal, concrete, wood etc. examples of liquid are water, milk, oil etc while that of gas are oxygen, nitrogen, CO₂

STRUCTURE OF MATTER

Matter is made up of discrete particles namely atom, molecules and ion.

• Atom: An atom is the smallest particle of an element which can have a separate existence. Atom is made up of a nucleus and a revolving electron around an orbit or shell. The nucleus consists of proton and neutron. The proton is positively charged, electron is negatively charge and neutron is neutral (i.e. has no charge). The number of protons equates the number of electrons .An atom that contains the same number of protons and electrons is said to be electrically neutral.
• Molecule: A molecule is a group of atoms of the same or different elements joined in simple proportion. They come together to make up matter

BROWNIAN MOTION

• Molecules exist
  • Molecules are continually in motion

EVALUATION

1. Explain the structure of matter
2. What is the importance of Brownie’s motion

MOLECULAR THEORY OF MATTER

Using kinetic theory explain the (i) definite structure of solid (ii) shape of liquid (iii) gas

• Solid: Matter consists of molecules which are tightly held together by intermolecular forces to make the molecules to vibrate about their mean positions, giving the solid definite shape. If the solid is heated, the total energy is divided among the molecules to make them vibrate faster. Eventually, they move so fast that they break loose from their fixed position.
• Liquid:  The molecules of a liquid can move about within the given volume of the container. Hence, liquid has its own size but no shape. If the liquid is heated, its molecules gain kinetic energy and move faster, until eventually molecules can escape from the surface. The liquid then vanishes and turns to gaseous state.
• Gas:  The molecules of a gas are also in constant motion like the liquid but comparatively far apart. They move at high speed, colliding with one another and with the walls of their containing vessel. They fill the vessel and exert pressure on the walls of the container. The pressure of the gas is caused by the collision of the molecules with the walls of the container.

DIFFUSION AND OSMOSIS

DIFFUSION: Diffusion is the process by which different forms of matter (fluids) mix intimately with one another owing to the kinetic nature of their molecules. It is also the tendency of a gas to mix with another and fill an empty space as a result of the constant random motion of the molecules.

The rates of diffusion or factors affecting diffusion are (i) density (ii) mass (iii) temperature (iv) pressure (v) concentration

Also, Graham’s law of diffusion states that at constant temperature, gas diffuse at rates inversely proportional to the square root of their vapour densities.

R α1/√M → R = K/√M    .;K = R√M

Hence, R1√M1 = R2√M2 = …= Rn√Mn

Hence, R1/R2 = √M2/√M1     where R  – rate of diffusion,  M – relative molecular mass. NB : (i) R = volume (gas)/time

(ii) Relative molecular mass is twice its vapour density

OSMOSIS: This is the movement of water molecules from the region of higher concentration to a region of lower concentration through a semi-permeable membrane.

EVALUATION

1. Using kinetic theory, explain the definite structure of solid
   1. State four factors that affect the rate of diffusion

READING ASSIGNMENT

Read more on atomic structure, diffusion and osmosis – New school physics (pg 87-92)

GENERAL EVALUATION

1. State Archimedes principle
2. State the law of floatation

WEEKEND ASSIGNMENT

1. The following are examples of theory except (a) concrete (b) oil (c) brick (d) metal
   1. The nucleus of an atom consist of (a) proton and electron (b) neutron and electron

(c) proton and neutron (d) none of the above

• Positive ions are called ____ (a) camions (b) anions (c) molecules (d) atom
  • When is atom said to be electrically neutral   (a) when the number of proton equals the number of neutron (b) when the number of protons equals the   number of electrons

(c) when the number of proton is greater then the number of electron   (d) when the number of neutron equals the number of electron

• Ion is a form of ____ (a) atom (b) molecules (c) matter (d) none of the above.

THEORY

1. Using kinetic theory, explain the definite structure of solid
   1. State four factors that affect the rate of diffusion