All the materials you can hold or touch are matter. Chapter 2 Matter All the materials you can hold or touch are matter.

What Is Matter? You are made of matter Your textbook is made of matter. The air you breathe is matter. Anything that has mass and occupies space is matter. Light, Sound, and Electricity are NOT matter because they have no mass or volume!

Matter All matter is made up of atoms. Element – a substance that cannot be broken down into simpler substances. Atom – the smallest particle that has the properties of an element Compound – a substance made of atoms of more than one element bound together.

Earth

Human Body

Matter Molecule – the smallest unit of a substance that exhibits all of the properties characteristic of that substance H2O CO2 Chemical formula – the chemical symbols and numbers indicating the atoms contained in the basic unit of a substance C16H10N2O2

Matter Pure substance – any matter that has a fixed composition and definite properties. CO2 - C3H8O H2O Mixture – a combination of more than one pure substance. Milk Grape juice Windex

Mixtures Homogeneous – mixing occurs between the individual units and is the same throughout Salt dissolved in water Heterogeneous – not uniformly mixed Flour suspended in water

Mixtures Miscible – describes two or more liquids that are able to dissolve into each other in various proportions Rubbing (denatured) alcohol Immiscible – describes two or more liquids that do not mix into each other. Oil and vinegar salad dressing

Matter and Energy

Kinetic Theory All matter is made of atoms and molecules that act like tiny particles. These tiny particles are always in motion. The higher the temperature, the faster the particles move. At the same temperature, more massive (heavier) particles move slower than less massive (lighter) particles.

Kinetic Theory The kinetic theory is a useful tool for visualizing the differences between the three common states of matter: solids, liquids, and gases Solids – have a rigid structure Liquids – have a less rigid structure than solids and can move about, or flow. Liquids have a definite volume that can be measured.

Kinetic Theory The kinetic theory is a useful tool for visualizing the differences between the three common states of matter: solids, liquids, and gases Gases – gases are in a constant state of motion and rarely stick together Gases will fill any container Due to their rapid movement, a gas exerts pressure on its container

Change of state for water Gaseous steam Relative energy 540 Calories per gm / C Liquid water 80 Calories per gm / C Solid ice 100 C 0 C

Change of state for water Gaseous steam Relative energy 540 Calories per gm / C Melting (energy absorbed) Freezing (energy released) Evaporation (energy absorbed) Condensation (energy released Liquid water 80 Calories per gm / C Solid ice 100 C 0 C

Energy’s Role Energy must be added to cause melting or evaporation Energy is transferred in all changes of matter Changing state does not change composition or mass Evaporation – the change of a substance from a liquid to a gas

Energy’s Role Sublimation – the change of a substance from a solid to a gas Dry ice (solid CO2) Ice and snow at very high altitudes will sublime Ice in your freezer at home will sublime Whether it is ice, water, or steam, water in any form is always made of H2O molecules.

Energy’s Role Law of Conservation of Mass – Matter can neither be created nor destroyed. Law of Conservation of Energy – Energy can neither be created nor destroyed. [See figure 2-17 on page 51 of text.] Mass A (wood + air) = Mass B (carbon + carbon dioxide + water)

Properties of Matter

Chemical and Physical Properties Chemical property – the way a substance reacts with others to form new substances with different properties. Involve the reactivity of elements or compounds Flammable Able to rust or oxidize Reactivity – the ability of a substance to combine chemically with another substance.

Chemical and Physical Properties Physical property – a characteristic of a substance that can be observed or measured without changing the composition of the substance. Physical Properties Shape, color, odor, texture Melting point, boiling point, density, strength, hardness, conductivity, etc.

Chemical and Physical Properties Melting point – the temperature at which a solid becomes a liquid Boiling point - the temperature at which a liquid becomes a gas (below the surface)

Chemical and Physical Properties Density – is calculated by dividing the object’s mass by its volume. D = m/V Buoyancy – the force with which a more dense fluid pushes a less dense substance upward

Density of some items Item Chem Formula Density g/cm3 Air Mixture 0.00129 Gasoline 0.7 Water H2O 1.00 Lead Pb 11.3 Iron Fe 7.86 Helium He 0.00018 Ice 0.92

Chemical and Physical Properties Properties help determine uses – Copper is used in electrical power lines, telephone lines, and electrical motors because of its good electrical conductivity. Ethylene glycol remains a liquid at temperatures that would normally boil or freeze in a car radiator. (Antifreeze)

Chemical and Physical Changes Materials that stay in the same state under normal conditions Surgical steel Concrete Glass Materials that change and combine Gasoline Car batteries Human metabolism (oxidation) Digestion, etc.

Chemical and Physical Properties Chemical changes are changes in composition

Chemical and Physical Properties Electrolysis – the process by which water can be broken down into hydrogen and oxygen. The atoms of oxygen and hydrogen are not destroyed, but rearrange themselves to form hydrogen and oxygen gas. [See figure 2-22 in text.] Burning of gasoline into C, CO2, & H2O A change in odor or color is a good clue that a substance is changing chemically i.e. food burning, paint fading, etc.

Chemical and Physical Properties Physical changes do not change composition Physical change – a change in the physical form or properties of a substance without a change in composition. Grinding Quartz crystals into sand Grinding peanuts into peanut butter Making gold jewelry