Chapter 15: Classification of Matter Section 1: Composition of Matter

Objectives Distinguish between substances and mixtures Identify the difference between elements and compounds Classify mixtures as solutions, colloids, or suspensions

Pure Substances The properties of materials can be used to classify them into categories. A substance is a type of matter that is always made of the same material or materials. A substance can be either an element or a compound.

What are elements? At your table, take 1 minute to try to define the word element. A substance is an element if all the atoms in the substance are the same. What are some examples of elements? How do you know they are elements?

More about elements More than 20 elements have been made in laboratories Most of the 20 synthetic elements are unstable

What are compounds? In your group, take 30 seconds to figure out the difference between an element and a compound. A compound is a substance with two or more elements that are combined in a fixed proportion. What is the fixed proportion for water?

More about compounds Many compounds look different from the elements in them. Compound Elements in the Compound Water (clear Liquid) H (clear gas) O (clear gas) Table Salt (white solid) Na (silvery metal) Cl (green-yellow gas) Carbon dioxide (clear gas) C (black solid) Table sugar (white solid)

Write your answers on your whiteboard . . . Define substance. Define element. Define compound. Is water a substance, an element, or a compound?

Mixtures A mixture is a material made up of two or more substances that can be easily separated. What is an example of a mixture? Is water a mixture? Why/why not? How do you know?

What are heterogeneous mixtures? A heterogeneous mixture is one in which different materials can be identified easily. Most of the mixtures around you are heterogeneous mixtures. Some heterogeneous mixtures are mixtures in themselves.

Heterogeneous: Yes or No Pizza Your shirt Salt Milk Water

Think About It How do you know that the water molecules from a faucet and the water molecules from a river are the same? What is the relationship between atoms, elements, compounds, and substances? How can you tell that a pizza is a heterogeneous mixture?

What are homogeneous mixtures? A homogeneous mixture contains two or more substance blended evenly throughout. You cannot see the different substances in a homogenous mixture. How is a homogenous mixture different from a heterogeneous mixture?

What is a solution? 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 their container. Vinegar and soft drinks are solutions.

Relationships to know . . . Use the words below for the diagram to the left . . . Homogeneous Heterogeneous Mixture Matter Compound Element Substance

Relationships filled in . . . Matter Has mass and volume Heterogeneous Unevenly mixed Mixture Variable composition Homogeneous Evenly mixed; a solution Substance Definite composition Compound 2+ kinds of atoms Element One kind of atom

What are colloids? A colloid is a type of mixture with particles that are larger than solutions, but not heavy enough to settle to the bottom of their container. Milk and paint are examples of colloids. Gases and solids can be colloids, like fog and smoke.

Colloid or Solution: What’s the Difference? Solution – cannot see light pass through it; light is invisible as it passes through Colloid – light scatters because of the particles in the colloid

Do you remember? What is a homogenous mixture? What is a heterogeneous mixture? What is a solution? What is a colloid?

What are suspensions? A suspension is a heterogeneous mixture containing a liquid in which you can see the particles settle. Why would a dam cause suspended particles to settle out of river water? Name a colloid you can see through.

Comparing Solutions, Colloids, and Suspensions Description Solutions Colloids Suspensions Settle upon standing? No Yes Separate using filter paper? Particle size 0.1-1 nm 1-100 nm >100 nm Scatter light?

Match the terms Colloid Compound Element Heterogeneous mixture A substance in which all the atoms are the same A homogeneous mixture of particles so small that they cannot be seen with a microscope and that will never settle to the bottom of their container A type of mixture with particles that are larger than those in solutions, but not heavy enough to settle to the bottom of their container A mixture that contains two or more substances blended evenly throughout The scattering of light particles in a colloid Colloid Compound Element Heterogeneous mixture Homogeneous mixture Solution Substance Suspension Tyndall effect