MATTER AND PHASE CHANGES

WHAT IS MATTER? Anything has mass and takes up space (middle school answer) Made up of atoms in constant random motion Atoms are the smallest unit of “stuff” Exists in four phases – solid, liquid, gas, and plasma

Solids Closely packed together due to strong intermolecular forces (IMF) holding them together Constantly vibrating, but do not readily slip past one another Has a definite shape (see above) Usually arranged in a regular pattern

Liquids Particles are in contact with each other due to IMF (these are weaker than those holding solids together) Particles have enough energy to partially overcome those IMF and can therefore slide past each other NO definite shape (see above) Takes the shape of the container No regular arrangement

Gases Not in contact with each other Have enough energy to overcome the IMF among the particles Move in straight lines until they bump into something, then the particle just bounces off Move through out the container since no IMF hold them together Fill the container No regular arrangement

Plasma Contains positively and negatively charged particles Substance converted to plasma phase at a very high temperature (think stars!!) High temp means particles are moving at a high speed. At these speeds, electrons are stripped from the atom, leaving the atom charged Most common state of matter in the UNIVERSE, but not on Earth. Found in stars Lightning bolts Neon and fluorescent light tubes Auroras

IMF AND BOILING POINTS Do you think a substance with a high boiling point has strong IMFs or weak IMFs? Explain your answer. (This is a great test question…Hint Hint! )

LET’S LOOK AT SOME BOILING POINTS… 1. DETERMINE THEIR STATES AT ROOM TEMP 2. CAN YOU SMELL THEM? 3. WHAT DO THESE THINGS TELL YOU ABOUT IMF?

HEATING CURVES Temperature = average kinetic energy Faster the particles move  the higher the temperature Phase change in terms of the Kinetic Molecular Theory (KMT) 1.Phase change is due to the movement (energy ) of the particles. 2.The freezing or melting point is the temperature where a phase change occurs between a liquid and a solid. If heat is being added at this temperature bonds between particles will break and a solid will melt. If heat is taken away bonds will form between particles and a liquid will freeze at this temperature. 3.The boiling point is the temperature where a liquid is changing to a gas throughout the liquid. Can occur at any temp. Boiling occurs when bubbles and vapor are present.

When energy (such as heat) is added to a substance, the energy of the particles of the substance increases. Evidence of this would be that the temperature of the substance increases or a phase change. Heat is added to a solid the particles will move faster and the temperature will increase until the temperature of the solid reaches its melting point. When the temperature of a solid is equal to the melting point and more heat is added to the substance the temperature will not change. The extra heat will be used to break some of the bonds between the molecules of the solid and change the phase to a liquid

Kinetic Molecular Theory Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion. These particles move in a straight line until they collide with another particle or the walls of the container. These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space. There is no force of attraction between gas particles or between the particles and the walls of the container. Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container. The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.

PHASE DIAGRAM

PHASE DIAGRAM OF CARBON DIOXIDE Triple Point – The point at where all three states of matter exists in equilibrium. Critical Point – the “end” of the phase diagram