Classification of Matter Chapter 18 Classification of Matter

Composition of Matter Pure Substances: A pure substance is something with a fixed composition. These can be either an element or a compound. ELEMENTS: All the atoms are alike. The periodic table is a list of the elements. Examples: Oxygen, Copper, Zinc, Hydrogen, Aluminum, Gold, Titanium, Tungsten, Lead

COMPOUNDS: Two or more elements combined in a fixed proportion and held together by some form of chemical bond. Examples: NaCl (Sodium chloride); H20 (water); H2SO4 (sulfuric acid); HCl; NaOH A particle consisting of two or more atoms that are covalently bonded together (by sharing electrons) is called a molecule. Sodium Chloride: Salt Oxygen: O2

MIXTURES: Two or more substances that can be separated by physical means is a mixture. In other words, a mixture contains substances that are NOT chemically bonded together…they are intermixed together. Heterogeneous Mixture is a mixture of different and easily distinguishable materials. Examples: trail mix, pond water, granite, concrete, dry soup mix, permanent press fabric A heterogeneous mixture containing a liquid in which visible particles settle is called a suspension. (pond or river water can be a good example)

Homogeneous Mixture contains two or more gaseous, liquid, or solid substances blended evenly together. A solution is a homogeneous mixture of particles so small that they cannot be seen with a microscope and will never settle to the bottom of the container. These remain constantly and uniformly mixed. Examples: tea; lemonade. Salt water; vinegar Colloid is a mixture with larger particles than solutions but they are not heaven enough to ever settle. They scatter light in the Tyndall effect. Examples: milk; fog; gelatin; paint; smoke One way to distinguish a colloid from a solution is to use the Tyndall effect. You will be able to see a beam of light as it shines through a colloid because the light will scatter. A beam of light will not be visible in a solution.

Properties of Matter Physical Property is a characteristic of a material that can be observed without changing the identity of the substance in the material. Examples: color, shape, size, melting point, boiling point, hardness, texture, density, state of matter (liquid, solid, of gas), etc. Appearance – observations involve the physical description of a substance

Appearance (continued) ….. Examples: Tennis ball A tennis ball is brightly colored hollow sphere. These are qualitative, descriptive observations of the ball’s physical properties. You can also measure some physical properties. You can measure the diameter, mass, and volume of the ball. These would be quantitative observations that require a number and a unit. Soft drink You can qualitatively describe a cup of soft drink as bubbly brown liquid. You can measure its temperature, volume, mass and density.

Behavior – observations involving how a substance acts Examples: magnetism (whether it attracts a magnet… and how hard), viscosity (how easily it flows), ductility (how easy it is to stretch it into a wire), malleability (how easy it is to pound it flat), volatility (how easily it evaporates), conductivity (how will it conducts electricity), solubility (how well it dissolves). Physical properties can be observed without changing the substance or material.

Physical properties such as size, solubility and magnetism can be used to separate mixtures. A magnet can be used to remove magnetic particles from a mixture. (like iron from sand) You can use a sieve to separate large seeds from smaller seeds, or gravel from sand. You can dissolve soluble compounds in water and separate them from insoluble particles using a filter. You get you soluble compound back by drying off the water. (this works to separate salt from sand) Distillation is another process for separating substances in a mixture by evaporating a liquid and condensing its vapor. Distillation can be used to separate a liquid from solids or to separate two or more liquids as long as they have different boiling points.

Physical change is a change in a substance’s size, shape, or state of matter. Examples: evaporation, condensation, melting, freezing, breaking, grinding, tearing. A substance does not change its identity when it undergoes a physical change. (a rock smashed to bits is still rock. Water frozen to make ice cubes is still water.)

Chemical property is a characteristic of a substance indicating that it can change chemically, such as flammability (tendency to burn) or light sensitivity. When one substance changes to another substance, a chemical change has occurred. Examples: burning (paper and oxygen change into carbon dioxide and water vapor), rusting (iron and oxygen change into iron oxide.)

Chemical changes can be indicated by Temperature change Production of sound Emission of light Smell Bubble formation (gas is evolved) Formation of a solid (precipitate) Chemical changes can occur very slowly Example: formation of rust. Chemical change can be used to separate substances such as metals from their ores. The law of conservation of mass says that the mass of all substances present before a chemical change equals the mass of substances after the change

States of Matter Every day you encounter different states of matter. A material’s physical state is due to differences in the attraction between the particles that make up the matter. The three common states of matter are solids, liquids, and gases. Solid State – The particles of a solid are packed closely together and are constantly vibrating in place. The attraction between particles are strong. Solids have a fixed volume and shape.

Liquid State – The attractive forces between particles are weaker than in a solid. The particles can slide past each other, allowing liquids to flow and take the shape of their container. Liquids have a definite volume, but not a definite shape Gas State – The particles are much farther apart than in a liquid or solid. The attractive forces between the particles are very weak so the particles do not cling together. Gases do not have a definite shape or volume. The particles are so far apart that a gas contains mostly empty space.

Changing States Melting – change from solid to liquid Freezing – change from liquid to solid Vaporization – change from liquid to vapor/gas (evaporation) Condensation – change from a gas/vapor to a liquid Remember that changes of state are physical changes. The identity of the material does not change, just the attractive forces and spacing between the particles.