15.1 Composition of Matter

Composition of Matter

Lesson 1

What are the differences between
substances and mixtures?

Focus Question

solution
homogeneous mixture
Tyndall effect
colloid
suspension
heterogeneous mixture
compound
element
substance

New Vocabulary

property: characteristic or essential quality

Review Vocabulary

• Matter is anything that takes up space and has mass

• A substance is a pure substance that has a fixed composition.

• A substance can be an element or compound.

Substances

• All substances are built from atoms.

• An element is a substance made up of atoms that are all alike.

• Copper and nitrogen are examples of elements.

• There are about 90 naturally occurring elements.

Substances

• A compound is a substance in which the atoms of two or more elements are
chemically combined in a fixed proportion.

• Water and table salt are examples of compounds.

Substances

• Many salad dressings are mixtures of oil, vinegar, and seasoning.

• A mixture is matter composed of two or more substances that can be separated by physical means.

• A heterogeneous mixture is a mixture in which different materials remain distinct.

• A green salad containing different vegetables is an example of a heterogeneous mixture.

Mixtures

• A suspension is a heterogeneous mixture made of liquid and solid particles that settle.

• A colloid is a heterogeneous mixture with particles that never settle. Paint, milk, fog, and smoke are
examples of colloids.

• A beam of light passes through a solution, but the light is scattered in a colloid.

• The scattering of a light beam as it passes through a colloid is call the Tyndall effect.

Mixtures

• A homogeneous mixture is a mixture that remains constantly and uniformly mixed and has particles that are so small that they cannot be seen with a microscope.

• Soft drinks that have carbonation are heterogenous mixtures. Flat soft drinks are homogeneous mixtures.

• A solution is the same thing as a homogeneous mixture.

Homogeneous mixtures

The concept map shows that mixtures can be either
heterogeneous or homogeneous. Pure substances can be elements or compounds.

Homogeneous mixtures

Multiple Choice

Which is a substance made up of atoms that are all alike?

• compound

• element

• solution

• colloid

Multiple Choice

Which is classified as a compound?

• copper, Cu

• cobalt, Co

• table salt, NaCl

• magnesium, Mg

Multiple Choice

Which term correctly classifies a tossed salad or taco?

• homogeneous mixture

• solution

• colloid

• heterogeneous mixture

Multiple Choice

Which scatters a beam of light as it passes through?

• Colloid

• Solution

• Mixture

• Suspension

Multiple Choice

Which is not a heterogeneous substance?

• fog

• milk

• flat soft drink

• smoke