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Chapter 17. Composition of Matter. Objectives. Objective: Define substances and mixtures. Objective: Identify elements and compounds. Objective: Compare and contrast solutions, colloids, and suspensions. CLE 3202.1.5 Evaluate pure substance and mixtures. Chemistry.
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Chapter 17 Composition of Matter
Objectives • Objective: Define substances and mixtures. • Objective: Identify elements and compounds. • Objective: Compare and contrast solutions, colloids, and suspensions. • CLE 3202.1.5 Evaluate pure substance and mixtures.
Chemistry The study of matter, its properties, and changes.
Atom The basic unit that makes up all matter.
A. Pure Substances A pure substance is made of only 1 type of matter.
A. Substance Either an element or a compound.
1. Elements • Matter with identical atoms (only 1 type of atom) • All the atoms in a substance are the same
Elements 118 total elements known (as of 2011, but this is changing? As research continues, so do the findings)
2. Compounds A compound is a substance with two or more elements chemically combined in a fixed proportion
Compounds • Different atoms (elements) are always combined in the same ratio.
b. Compounds can only be separated (broken apart) into different elements by chemical or electrical processes.
c. Common Compounds • H2O = water • NaCl = salt • C6H12O6 = sugar / glucose
B. Mixture • Two or more substances that are NOT chemically combined • Can be easily separated by physical means
1. Homogeneous Homogeneous mixture contains two or more gaseous, liquid or solid substances blended evenly; you can not easily see the parts.
a. Solutions Liquid homogeneous mixtures with particles so small they can not be seen without a microscope.
Solutions The particles remain constantly and uniformly mixed. (Kool-aid, tea, salt-water)
2. Heterogeneous Mixtures • Mixture of different materials that can be easily seen and separated. • Mixtures of materials that are not evenly blended.
3. Colloid Heterogeneous mixture with larger particles that never settle.
Colloid • Colloids scatter light in the Tyndall effect. Particles in the colloid are large enough to scatter light, but those in the solution are not.
Tyndall effect Colloid
Colloids Examples: jello, milk, smoke, fog, whipped cream
4. Suspension A heterogeneous mixture containing a liquid in which visible particles that settle out on standing.
Suspensions • One material is denser than the other so a substance will float and never mix with the other. • Examples: oil and water, muddy water, vegetable soup
Composition of Matter 1 Suspensions • The table summarizes the properties of different types of mixtures.
Section Check 1 Question 1 A _______ is a type of matter with a fixed composition. A. colloid B. mixture C. substance D. solution
Section Check 1 Answer The answer is C. A substance can be either an element or a compound.
Section Check 1 Question 2 How many elements are found on Earth? A. 5 B. 10 C. 30 D. 90
Section Check 1 Answer The answer is D. About 90 elements are found on Earth, and more than 20 have been made in laboratories.
Section Check 1 Question 3 How are compounds different from mixtures?
Section Check 1 Answer The atoms in compounds are combined in fixed proportions and cannot be separated by physical means. A mixture is made of two or more substances that can be easily separated by physical means.
Question 4 How can a solution be distinguished from a colloid?
Answer Use the Tyndall effect to observe that colloids scatter light.
Objectives • Objective: Define substances and mixtures. • Objective: Identify elements and compounds. • Objective: Compare and contrast solutions, colloids, and suspensions. • CLE 3202.1.5 Evaluate pure substance and mixtures.