Learning outcomes Compare the properties of solids, liquids and gases Describe quantitatively the molecular structure of solids, liquids and gases, relating their properties to the forces and distances between molecules and to motion of molecules Describe the relationship between motion of molecules and temperature

8.1 States of Matter Three states of matter Solid Liquid Gas For example, iceberg, sea water and steam

8.1 States of Matter Properties of Solids, Liquids and Gases Solid Fixed shape Fixed volume Does not have fixed shape Assumes shape of container No fixed shape No fixed volume Assumes the shape and volume of container Not compressible Not easily compressible Highly compressible Does not flow easily Flows easily

8.1 States of Matter Molecular Structure of Solids, Liquids and Gases Distances between molecules Molecules arranged close together in regular pattern Incompressible because molecules are close together with little space between them

8.1 States of Matter Molecular Structure of Solids, Liquids and Gases Forces between molecules Balanced forces between molecules hold them in fixed positions Molecules vibrate about fixed positions, alternately attracting and repelling one another Strong attractive forces prevent molecules from leaving fixed positions while repulsive forces between atoms prevent them from collapsing into one another. Attractive and repulsive forces explains why a solid has fixed shape and fixed volume.

8.1 States of Matter Molecular Structure of Solids, Liquids and Gases Motion of the molecules When a solid is heated, molecules gain energy and vibrate more. Separation between molecules increase slightly and the solid expands.

8.1 States of Matter Molecular Structure of Solids, Liquids and Gases Distances between molecules Molecules not arranged in regular pattern Molecules slightly further apart than in solids Liquids cannot be easily compressed as molecules are close together with little space between them.

8.1 States of Matter Molecular Structure of Solids, Liquids and Gases Forces between molecules and motion of the molecules Molecules vibrate to and fro, alternately attracting and repelling one another. Molecules not held in fixed position by attractive forces. Molecules move among one another throughout the liquid. Explains why liquids flow and take the shape of container

8.1 States of Matter Molecular Structure of Solids, Liquids and Gases Forces between molecules and motion of the molecules Attractive forces between molecules make it difficult for molecules to leave the liquid. Thus liquids have fixed volume. When a liquid is heated, molecules vibrate and move about more vigorously. Thus liquid expands, but only very slightly.

8.1 States of Matter Molecular Structure of Solids, Liquids and Gases Distances between molecules Molecules are far apart Mainly empty space between molecules That is why gas can be compressed easily.

8.1 States of Matter Forces between molecules & motion of molecules Molecules move randomly at high speed Intermolecular repulsive forces act only when molecules collide with one another and with the walls of container. Molecules are so far apart that intermolecular attractive forces are negligible in a gas. A gas is thus able to expand and fill a container completely.

The three states of matter are solid, liquid and gas.

8.2 Kinetic Model The kinetic theory of matter states that all matter is made up of a large number of tiny atoms or molecules which are in continuous motion. Molecules are too small to be seen directly. Existence of particles in continuous motion has been demonstrated by Brownian motion and diffusion.

8.2 Kinetic Model Motion of Molecules and Temperature When temperature increases, thermal energy of the molecules increases and the molecules move faster. The molecules gain kinetic energy.

When the temperature increases, kinetic energy of the molecules also increases.