Chemistry

Thursday, September 13, 2013How Can Density Be Used to Identify A

substance Lab

What is the volume of a 36 g rock if its density is

25 g/ml?

What is the mass of a brick if its density is 8.9g/cm3, and the bricks dimensions are 2cm x 11cm x 8cm?

Bell Work 9/16

Discuss Classification of Matter Complete Classification Activity

Agenda

Students will be able to:

Classify matter into different categories Use density to identify a substance

Objectives

Classification of Matter

Matter can be classified into many different categories.

The next few slides we will be going over each of these categories

Classification of Matter

How are they similar? . . . Different?

Only one type of matter in sample

Water (H2O) Muddy Water

Classification of Matter

Pure Substance

Only one type of matter in sample

Water (H2O)

Classification of Matter

Pure Substances – How are they different

Water (H2O) Gold (Au)

Classification of Matter

Pure Substances – Element

Gold (Au)

Atoms of only one type are in the substance

Classification of Matter

Pure Substances – Compound

Water (H2O)

Atoms of more than one type are in the substance

Classification of Matter

Mixture

Two or more types of matter in the sample

Chicken Soup

Classification of Matter

Mixtures – How are they different?

Chicken Soup Cola

Classification of Matter

Heterogeneous Mixture

Mixture is not the same throughout—Can identify different parts

Chicken Soup

Classification of Matter

Homogenous Mixture

Mixture is the same throughout

Cola

A. Matter Flowchart

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture

Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed? noyes

Is the composition uniform?

noyes

Colloids Suspensions

A. Matter Flowchart

Examples:

graphite

pepper

sugar (sucrose)

paint

soda

• Element

• Hetero. Mixture

• Compound

• Hetero. Mixture

• Homo. Mixture

B. Pure Substances

Element composed of identical atoms EX: copper wire, aluminum foil

B. Pure Substances

Compound

composed of 2 or more elements in a fixed ratio

properties differ from those of individual elements

EX: table salt (NaCl)

Compound Example

C. Mixtures

Variable combination of 2 or more pure substances.

Heterogeneous Homogeneous

Tyndall Effect

https://www.youtube.com/watch?v=SoUmz8L87Z4

C. Mixtures

Solution homogeneous very small particles no Tyndall effect Tyndall Effect

particles don’t settle EX: rubbing alcohol

C. Mixtures

Colloid heterogeneous medium-sized particles Tyndall effect particles don’t settle EX: milk

C. Mixtures

Suspension heterogeneous large particles Tyndall effect particles settle EX: fresh-squeezed

lemonade

C. Mixtures

Examples:

mayonnaise

muddy water

fog

saltwater

Italian salad dressing

colloid

suspension

colloid

solution

suspension

Physical vs. Chemical Properties

Physical Property

Can be observed without changing the identity of the substance

Chemical Property

Describes the ability of a substance to undergo changes in identity

B. Physical vs. Chemical Properties

Examples:

melting point

physical

flammable

chemical

density physical

magnetic

physical

tarnishes in air chemical

Physical vs. Chemical Change

Physical Change Changes the form of a substance without

changing its identity Properties remain the same Reversible

Chemical Change Changes the identity of a substance Products have different properties Irreversible

Physical vs. Chemical Change

Signs of a Chemical Change

change in color or odor

formation of a precipitate (solid)

formation of a gas

change in light or heat

Physical vs. Chemical Change

Examples:

rusting iron chemical

dissolving in water physical

burning a match chemical

melting ice physical

grinding salt physical

Classifying Matter Activity

Get out a sheet of paper and put your name on the top.

Create a data chart with the following headings

Make 20 rows and label 1-20 in the column “vial number”

Vial Number Name of Material

Pure Substance or

Mixture

Element, Compound,

Hetero or Homo geneous

Reasoning(Why did you

classify it as this?)

Classifying Matter Activity

You will pair up and sit with your partner on one side of each lab table with 1 group at the back table if needed.

I will come give you a vial with matter in it, you will write the name of the matter in the appropriate column, decide whether it is a pure substance or a mixture and then what type of pure substance or mixture. Then pass it on to the next group

Analysis1. Which classification was hardest to determine-

Element, Compound, Heterogeneous or Homogenous? Why was this the hardest one?

2. If you had to separate the heterogeneous mixtures into colloids or suspensions, what property would you look at to separate the two?

3. Determine whether each sample below is an element, compound, heterogeneous or homogeneous mixture

A B C D E