Substances, Mixtures, Properties and Changes of Matter Section 1.4 – Pages 8 -13

What is Chemistry? Chemistry is the study of the composition, structure and behavior of matter Composition – what is matter made up of? Structure – how is the matter put together? Behavior – how do different types of matter interact? Matter = anything that has mass and takes up space

The Atom All matter is made up of small particles called atoms. Atom: The fundamental unit of which elements are made.

Pure Substances Substance – contains only one kind of matter; cannot be separated into other kinds of matter by any physical process. There are two types: Elements Compounds Coal = Carbon

Elements Element: simplest form of matter, cannot be decomposed into simpler substances by any chemical reaction; located on the periodic table Examples – oxygen, gold, sulfur Bars of Gold

Elements in the Human Body

Compounds Compounds: contains 2 or more elements chemically combined; can only be separated using chemical reactions Examples – water (H2O), sugar (C12H22O11), carbon dioxide (CO2) Sucrose

Law of Definite Proportions A pure compound always contains definite or constant proportions of the elements by mass. Example: H2O (water) vs. H2O2 (hydrogen peroxide)

Molecules Molecule: A collection of atoms bonded together that behave as a unit. All molecules of the same compound are identical.

Mixtures Mixture – physical blend of 2 or more substances; can be easily separated by heating, filtering, drying, sorting, dissolving, etc. There are two types: Heterogeneous Homogeneous

Homogeneous Mixture Homogeneous Mixture – uniform composition; any sample has the same composition (aka solution) Examples - Salt water, air, brass (alloy) Salt Water Solution

Heterogeneous Mixture Heterogeneous Mixture – not uniform in composition; consists of physically distinct parts, each with different properties. Examples – salsa, concrete, toss salad Chex Mix!

Review – Classifying Matter Chemistry is the study of the __________________, ___________________ and ___________ of matter. Matter is anything that has ____________ and ___________________. Classify the following as either an element, compound, homogeneous mixture or heterogeneous mixture. A penny Silicon Apple juice Vanilla yogurt with M & M’s Carbon dioxide

Separation of Mixtures Two Examples: Distillation: a separation process that depends on the different boiling points of the substances. Filtration: separation of a solid from a liquid by using filter paper

Properties of Matter Physical Properties: a characteristic of matter that can be observed or measured w/o changing the samples composition Examples – density, odor, color, melting pt, solubility, state, etc. Chemical Properties: the ability or inability of a substance to combine with or change into one or more new substances (reactivity) Examples – ability of iron to rust, flammability

Intensive vs. Extensive Properties Intensive Property – independent of the amount of substance present Examples – density, boiling pt., melting pt. Extensive Property – dependent upon the amount of substances present Examples – mass, length, volume

Physical or Chemical Property Classify the following as either physical or chemical properties: The boiling point of a certain alcohol is 78 °C. Diamonds are very hard. Sugar ferments to form alcohol. A metal wire conducts an electric current.

Changes of Matter Physical Changes: a type of change that alters the physical properties of a substance not its composition (identity) Example s– cutting of paper, grinding, melting, dissolving, etc. Chemical Changes: chemical reactions; a process involving one or more substances changing into new substances; “irreversible” Examples – rusting, photosynthesis, burning

Evidence of Chemical Changes: Creation of a gas Odor is released Color change Energy is absorbed or released

Three States of Matter Solid: definite shape and volume; particles are tightly packed together forming a rigid structure; incompressible Liquid: definite volume and takes shape of its container; particles “flow”; incompressible Gas: takes shape and volume of its container; particles are far apart; can be compressed