Section 1—Composition of Matter Chapter 17 Section 1—Composition of Matter

Section 1 Pure Substances- Elements- Either an element or a compound that cannot be broken down into simpler components and still maintain the properties of the original substance ex: helium, aluminum, water, salt Elements- a substance whose atoms are all alike *there are 90 found in nature/20 others made in labs

Compounds A substance in which the atoms of two or more elements are combined in a fixed proportion Ex: water, chalk, etc. Compounds usually look different from the elements in them (salt—Na and Cl)

Heterogeneous Mixtures: A material made up of two or more substances that can be easily separated by physical means Heterogeneous Mixtures: A mixture in which different materials can be distinguished easily Ex: granite, concrete, pizza Homogeneous Mixtures: Contains two or more gaseous, liquid or solid substances blended evenly throughout Ex: soft drinks, vinegar, etc

Solution- A homogeneous mixture of particles so small that they cannot be seen with a microscope and will never settle to the bottom of their container Ex: Colloid: A type of mixture that never settles It’s particles are larger than those in solutions but not heavy enough to settle Ex: some paints, shampoos, hairgel,

The scattering of light by colloidal particles Tyndall Effect: The scattering of light by colloidal particles A light beam is invisible as it passes through a solution, but can be seen readily as it passes through a colloid Ex: pg. 523

Suspensions: A heterogeneous mixture containing a liquid in which visible particles settle ex: muddy pond water (visible particles settle out eventually)

SECTION 2—Properties of Matter Physical Properties- Any characteristic of a material that can be observed without changing the identity of the substance Ex: color, shape, size, melting/boiling pt, etc. Physical Properties may be used to separate substances (in a mixture)

Physical change a change in size, shape or state of matter (might involve energy changes but element or compound itself does not change) *PHYSICAL CHANGES ARE PHASE CHANGES!! Distillation- process for separating substances in a mixture by evaporating a liquid and recondensing its vapor

Chemical properties Chemical Change: A characteristic of a substance that indicates whether it can undergo a certain chemical change Ex: flammability, exposure to light Chemical Change: A change of one substance to another Ex: foaming of antacid tablets, silver tarnishing, etc. *A NEW SUBSTANCE IS FORMED BY A CHEMICAL CHANGE!!!!

Weathering—Chemical or Physical? Some weathering changes are physical and some are chemical Physical—rocks split, streams cut through rock, etc. Chemical—calcium carbonate from limestone changes to calcium hydrogen carbonate Ex: White Cliffs of Dover

The Conservation of Mass Law of Conservation of Mass Matter is neither created nor destroyed (during a chemical change) The mass of all substances that are present before a chemical change EQUALS the mass of all the substances that remain after the change