Transcript Chapter 15 ppt.
15
15 Table of Contents
Unit 4: The Nature of Matter
Chapter 15: Classification of Matter
Composition of Matter 15.1
Elements
• • All substances are built from atoms.
element
– Pure Substance- all the atoms in a have the same identity • Examples: ?
15.1
Composition of Matter
Elements
• About 90 elements are found on Earth. • More than 20 others have been made in laboratories, but most of these are unstable and exist only for short periods of time.
Composition of Matter 15.1
Compounds
• Compound- two or more elements combine to form substances (has a specific chemical composition) • Examples?
15.1
Composition of Matter
Compounds
15.1
Composition of Matter
Mixtures
• A mixture- Material made up of two or more substances that can be easily separated by physical means. • Examples?
15.1
Composition of Matter
Heterogeneous Mixtures
•
heterogeneous mixture
-A mixture in which different materials can be distinguished easily • Examples?
15.1
Composition of Matter
Heterogeneous Mixtures
15.1
Composition of Matter
Homogeneous Mixtures
Composition of Matter 15.1
Homogeneous Mixtures
•
Homogeneous mixture
two or more gaseous, liquid, or solid substances blended evenly throughout. • Examples?
Composition of Matter 15.1
•
Homogeneous Mixtures Solution
– • (AKA- homogeneous mixture) • Particles cannot be seen with a microscope • Will never settle to the bottom of their container.
Composition of Matter 15.1
Colloids
•
colloid
-Mixture with particles that are larger than those in solutions but not heavy enough to settle out. • Not homogeneous or heterogeneous • Examples?
15.1
Composition of Matter
Detecting Colloids
•
Tyndall effect
scattering of light by colloidal particles
15.1
Composition of Matter
Suspensions
•
suspension
, which is a heterogeneous mixture containing a liquid in which visible particles settle. • Examples?
Composition of Matter 15.1
Suspensions
• The table summarizes the properties of different types of mixtures.
Section Check 15.1
Question 1
A _______ is a type of matter with a fixed composition.
A. colloid B. mixture C. substance D. solution
Section Check 15.1
Answer
The answer is C. A substance can be either an element or a compound.
Section Check 15.1
Question 2
How many elements are found on Earth?
A. 5 B. 10 C. 30 D. 90
Section Check 15.1
Answer
The answer is D. About 90 elements are found on Earth, and more than 20 have been made in laboratories.
Section Check 15.1
Question 3
How are compounds different from mixtures?
Section Check 15.1
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.
15.2
Properties of Matter
Physical Properties
•
physical property
- characteristic of a material that you can observe without changing the identity of the material. • Examples: color, shape, size, density, melting point, and boiling point. • Item Examples:
15.2
Properties of Matter
Behavior
Properties of Matter 15.2
Physical Change The Identity Remains the Same
•
physical change
state of matter.
-A change in size, shape, or • Examples?
15.2
Properties of Matter
The Identity Remains the Same
15.2
Properties of Matter
Using Physical Change to Separate
•
Distillation
- Separating substances in a mixture by evaporating a liquid and recondensing its vapor
15.2
Properties of Matter
Distillation
Properties of Matter 15.2
Chemical Properties and Changes
•
chemical property-
characteristic of a substance that indicates whether it can undergo a certain chemical change.
• Examples?
Properties of Matter 15.2
Detecting Chemical Change
• If you leave a pan of chili cooking unattended on the stove for too long, your nose soon tells you that something is wrong. • This burnt odor is a clue telling you that a new substance has formed.
Properties of Matter 15.2
The Identity Changes
•
chemical change
- A change from one substance to another • Indications of chemical change: • Odor • Temperature Change • Formation of gas/solid • Color Click image to view movie
15.2
Properties of Matter
The Conservation of Mass
15.2
Properties of Matter
The Conservation of Mass
•
Law of conservation of mass
, the mass of all substances equal the mass of all the substances that remain after the change. • no mass is lost during a chemical or physical reaction.
Section Check 15.2
Question 1
Which of the following is a chemical property?
A. boiling point B. density C. flammability D. melting point
Section Check 15.2
Answer
The answer is C. Flammability indicates whether a substance will undergo the chemical change of burning.
Section Check 15.2
Question 2
A characteristic of a material that can be observed without changing the identity of the substances that make up the material is a _______.
Section Check 15.2
Answer
The answer is physical property. Examples of physical properties include color, shape, and density.
Section Check 15.2
Question 3
What is the law of conservation of mass?
Section Check 15.2
Answer
According to the law of conservation of mass, the mass of all substances that are present before a chemical change equals the mass of all substances that remain after the change.
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