Matter

“Food Matters” Is it a Pure Substance or a Mixture? • Matter can be divided into two main

categories: – Pure substances are homogeneous throughout.

They have the same chemical properties no matter where the sample is obtained or how large the sample is.

– Mixtures are combinations of two or more substances, with each substance retaining its chemical identity.

“Food Matters”

Is it a Pure Substance or a Mixture? • Distilled Water – PS Corn Flakes - M• Bottled Water – M White Vinegar - M• Tap Water – M Corn Starch - PS• OJ – M Plain Choc - M• Milk – M Crunch Bar - M• Sugar – PS• Salt - PS

Chemistry is the study of …

• ….Matter• Matter is

anything that takes up space and has mass.• Light and

sound are NOT matter!!

MATTER IS MADE UP OF…• …Atoms• The smallest

particle of an element

• Indivisible

….that guy is Democritus– Greek philosopher– “atomos”

What Does an Atom Look Like?

• Atoms are too small to see with the eye, but if we could see them, they would look like this….

• But we can see GROUPS of atoms.

Groups of Atoms are Called…

• …Elements• …made of IDENTICAL

atoms.

• Examples: Anything on the Periodic Table

Elements can combine to form…• …Compounds • …contain 2 OR MORE DIFFERENT

ELEMENTS (atoms) and are BONDED (attached) or joined in a fixed proportion

• Compounds are NOT on the Periodic Table;

• Compounds are NOT MIXTURES (we’ll get to those later…)

Identify these as Element(s) or Compound(s).

A B C D

1 Element 1 Compound 2 Elements 2 Elements

Classifying Matter

• All matter is made out of atoms…• And all matter can be classified into different

categories!– Pure Substances– Mixtures

Mixture• MIXTURES CAN BE SEPARATED!• Made up of 2 or more elements or compounds

– Yellow – an ELEMENT– Red/Blue – a COMPOUND

(Atoms are not really colored. The different colors represent different elements.)

Pure Substances (or simply, a substance)

• CANNOT BE SEPARATED • Can be made up of all one element OR all one

compound• Examples: – table salt – table sugar

• Element

• Compound

Identify these as Pure Substances or Mixtures.

A B C D

Pure Pure Mixture Mixture

1 element 1 compound 2 elements 2 elements

Pure Substances v. Mixtures

Video

Mixtures• A combination of more than one

type of substance• The properties of a mixture can

vary because the make up of a mixture is not fixed (unlike compounds which have a fixed proportion)

• 2 Types of Mixtures:– Heterogeneous – the parts of the mixture are noticeably different from one another

– Homogeneous – the parts of the mixture are so evenly distributed that it appears to be all the same substance (but a mixture is more than one substance!)

Solutions and Suspensions and Colloids…Oh My!

• A mixture can be further classified into 3 categories based on the size its largest particles– Solutions– Suspensions– Colloids

Solutions and Suspensions and Colloids…Oh My!

• Solutions – homogeneous mixtures– Examples: Sugar dissolved in water, tap water

– Properties of solutions:• DO NOT separate into layers over time• If liquid solutions are poured through a filter

none of the substance gets trapped in the filter.• You can see through liquid solutions

– All of these relate to the size of the particles - in a solution, they are tiny!

Homogeneous Mixture

• Substances are evenly distributed

• Appears to contain only one substance

• Solutions – homogeneous mixtures in which one substance dissolves in another

Solutions and Suspensions and Colloids…Oh My!

• Suspensions – heterogeneous mixtures– Example: sandy water– Properties of solutions:• DO separate into layers over time• If you pour a suspension through a filter some of

the substance in the mixture gets trapped in the filter.• Suspensions are cloudy because light gets

scattered in all directions as it hits larger particles.

– All of these relate to the size of the particles - in a suspension, they are bigger!

Heterogeneous Mixture

• The parts of the mixture are noticeably different from one another

• Suspensions– Separate into

layers

Heterogeneous Mixture

• Suspensions can be mixed (“Shake before serving) but eventually separate out.

Solutions and Suspensions and Colloids…Oh My!

• Colloids– somewhere in between homogeneous and heterogeneous

mixtures– Examples: milk and fog– Properties of colloids:

• DO NOT separate into layers over time.• Cannot use a filter to separate the parts of a colloid• Light gets scattered when it passes into a colloid

– Contain intermediate sized particles

How Do You Separate A Mixture?

• REMEMBER THE LAB?• Here are a few other ways to separate

mixtures….

Separation of Mixtures

• Compounds and mixtures differ in another way.

• It is difficult to separate a compound into each element.

• Mixtures can be easy to separate into its components because each component keeps its own properties.

Separation of Mixtures

1. Magnetic attraction: The magnetic components of a mixture can be separated by using a magnet.

Separation of Mixtures2. Filtration: separates parts of a

heterogeneous mixture by pouring it though a filter, the larger particles (residue) will be held in the filter while the smaller ones (filtrate) will pass through.

Separation of Mixtures

3. Distillation: used to separate components of a homogeneous mixture based on their different boiling points. Solution is heated and substance with lower boiling points evaporates and passes through a tube where it cools and turns back into water in another container.

Separation of Mixtures

4. Evaporation: When a mixture contains a solvent such as water and a solute such as salt, the solvent can be allowed to evaporate, leaving behind the solute.

Separation of Mixtures

5. Sedimentation: occurs naturally when solid substances that are heavier than their solvent deposit at the bottom of the mixture.

Separation of Mixtures

6. Decantation: a heterogeneous mixture that has distinct layers can be separated by slowly pouring one of the layers into another container.