MATTER AND TEMPERATURE

Chapter Ten: Matter and Temperature  10.1 The Nature of Matter  10.2 Temperature  10.3 The Phases of Matter

Chapter 10.1 Learning Goals  Define matter.  Identify the atom as the building block of matter.  Explain the basis for classifying matter as either pure substances or mixtures.

Investigation 10A  Key Question:  Is the matter a pure substance or is it a mixture? Pure Substance or Mixture

10.1 The Nature of Matter  Matter is a term used to describe anything that has mass and takes up space.  Greek philosophers Democritus and Leucippus proposed that matter is made of tiny particles called atoms.  Atoms were an idea that few believed.  The first evidence was called Brownian motion for Robert Brown, who first noticed the jerky motion of tiny particles.

10.1 The Nature of Matter  Varying the mass and size of particles that collide can have different effects.  Throwing marbles at a tire tube moves the tube smoothly.  Throwing the same marbles at a foam cup moves the cup in a jerky way, like Brownian motion.

10.1 Elements  An element is a pure substance that cannot be broken down into other substance by chemical or physical means.  All of the matter you are ever likely to experience is made from one or more elements in nature.

10.1 Elements  For example, water can be broken down into its elements, hydrogen and oxygen, when energy is added.

10.1 Atoms  A single atom is the smallest particle that retains the chemical identity of the element.

10.1 Atoms  Carbon atoms are different from sodium, aluminum, or oxygen atoms.  They have different masses.

10.1 Compounds and elements  Compounds are two or more different elements chemically bonded together.

10.1 Examples of compounds  Compounds contain more than one type of atom chemically joined together.

10.1 Molecules  A molecule is a group of two or more atoms joined together chemically.

10.1 Mixtures  Many substances you encounter are a mixture of different elements and compounds. How many atoms are in this mixture? How many molecules are in this mixture?

10.1 Elements, compounds, and mixtures Can you distinguish between atoms and molecules in these images?

10.2 Temperature  There are two common temperature scales.  On the Fahrenheit scale, water freezes at 32 degrees and boils at 212 degrees.  The Celsius scale divides the interval between the freezing and boiling points of water into 100 degrees.

10.2 What temperature really is  Atoms are in constant motion, even in a solid object.  The back-and-forth jiggling of atoms is caused by thermal energy, which is a kind of kinetic energy.

10.2 What temperature really is  Temperature measures the kinetic energy per molecule due to random motion.

10.2 Converting to Kelvin  The Kelvin temperature scale is useful in science because it starts at absolute zero.  To convert from Celsius to Kelvin, you add 273 to the temperature in Celsius.

10.3 Phases of Matter  On Earth, pure substances are usually found as solids, liquids, or gases.  These are called phases of matter.

10.3 The phases of matter  A solid holds its shape and does not flow.  The molecules in a solid vibrate in place, but on average, don’t move far from their places.

10.3 The phases of matter  A liquid holds its volume, but does not hold its shape—it flows.  Liquids flow because the molecules can move around.

10.3 The phases of matter  A gas flows like a liquid, but can also expand or contract to fill a container.  A gas does not hold its volume.  The molecules in a gas have enough energy to completely break away from each other.

10.3 The phases of matter  When they are close together, molecules are attracted through intermolecular forces.

10.3 The phases of matter  The forces in chemical bonds are stronger than intermolecular forces.

10.3 Intermolecular forces

 Within all matter, there is a constant competition between temperature and intermolecular forces.  When temperature wins the competition, molecules fly apart and you have a gas.  When intermolecular forces win the competition, molecules clump tightly together and you have a solid.

10.3 Melting and boiling  The melting point is the temperature at which a substance changes from a solid to a liquid.

10.3 Melting and boiling  The temperature at which a liquid becomes a gas is called the boiling point.

Notice temperature is constant while ice melts!

10.3 Melting and boiling points of common substances  Materials have a wide range of melting and boiling points.

10.3 Sublimation  Sometimes a solid can change directly to a gas when heat energy is added.  This process is called sublimation.

10.3 Plasma  In the plasma phase, matter becomes ionized as electrons are broken loose from atoms.  The Sun is made of plasma, as is most of the universe, including the Orion nebula.