Classification of Matter Chapter 17 p. 517-541. Composition of Matter Chapter 17 Section 1 p. 518-525.

Classification of Matter

Chapter 17

p. 517-541

Composition of Matter

Chapter 17

Section 1

p. 518-525

Pure Substances

• Have you ever looked at a picture and couldn’t tell whether it was a painting or copy? Did you go up and touch it?

• The properties of materials can be used to classify them into categories.

Pure Substances

• Materials are either pure substances or a mixture of substances.

• Pure substances – AKA substance – are either an element or compound

Pure Substances

• Substances can’t be broken down into simpler substances and still have the same properties

• Ie – what are the properties of a piece of gum?

• If I break it into smaller pieces, does it still have those properties?

• Ie – what are the properties of water?• If I separate a bottle of water into different

glasses, is it still water?

Elements

• Remember:– An atom is the smallest piece of

matter that still retains the properties of the element.

• All substances are made from atoms.

• If all the atoms in a substance are alike, it is called an element.

Elements

• Ie – the graphite in your pencil is an example of an element. – All the atoms in the graphite are carbon atoms

• Ie – the copper covering on your penny is an example of an element.– All the atoms that make up the covering are

copper atoms.

• Ie – the zinc in the middle of your penny is an example of an element. – All the atoms that make up your penny center

are made of the element zinc.

Elements

• There are 90 elements found in nature• Over 20 have been made in laboratories

– These are usually unstable and don’t last long

•Some elements you might recognize in your everyday life.

Copper pot or pan

Compounds

• Two or more elements can combine to form a compound

• These elements combine in a fixed proportion • Ie - water is a compound in which 2 hydrogen

atoms combine with 1 oxygen atom • Can you imagine putting a silvery metal and a

greenish-yellow, poisonous gas on your food??

Compounds

• You may have if you dashed some salt on your food today!

• Salt is a compound made up of the 2 elements sodium and chlorine

• Like salt, compounds usually look different from the elements in them

Mixtures

• Who enjoys eating pizza and pop for lunch?

• If so, then you enjoy 2 foods that are classified as mixtures

• A mixture, such as pizza or pop, is a material made up of two or more substances that can be easily separated by physical means.

Mixtures

• Heterogeneous Mixtures:• Unlike compounds, mixtures aren’t always

made of the same proportions of the substances that make them up.

• Remember that pizza? The chef doesn’t measure out precisely how much of each topping is sprinkled on. Plus, you can easily see most of the toppings on the pizza

• A mixture in which different materials can be distinguished easily is called a heterogeneous mixture

• Other examples: granite, dry soups, concrete

Mixtures

• Homogeneous Mixtures:• Remember that pop? It’s an example of a

homogeneous mixture• A homogeneous mixture contains 2 or more

substances blended evenly throughout• These mixtures are also known as solutions• Solutions remain constantly and uniformly mixed• Other example: Vinegar

Mixtures

• What kind of mixture is a solution??

Element, Compound, Mixture

Colloids

• A colloid is a type of mixture that never settles

• Its particles are larger than those in solutions but not heavy enough to settle

• Examples: Milk, paint, fog

Colloids• Detecting Colloids:• To tell for certain if a liquid is a colloid, pass a

beam of light through it• A light beam is invisible as it passes through a

solution, but can be seen when passing through a colloid

• This occurs because the particles in a colloid are large enough to scatter light

• The scattering of light by colloidal particles is called the Tyndall effect

• Can you think of any other colloids?

Website

• http://www.brainpop.com/science/matter/compoundsmixtures/index.weml

Properties of Matter

Section 2

p. 526-533

Physical properties

• Physical properties are observations that you make without changing the identity of the substances that make up the material

• For instance, you can stretch a rubber band or bend a piece of wire

• The ability to stretch or bend are physical properties

• Some other physical properties are color, shape, size, melting point, and boiling point

Physical Properties

• Appearance:

• How would you describe a tennis ball? (shape, color, state of matter)

• How would you describe a soft drink? (color, state of matter, taste)

• You could also measure its volume and temperature—these are all physical properties

Physical Properties• Behavior:• Some physical properties

describe the behavior of a substance

• For instance, objects containing iron (I.e. safety pins) are attracted by a magnet

• Remember that soft drink? If you were to knock it over, it would spread onto the table and floor—the ability to flow is a physical property of liquids

Physical Propertiesto Separate

• Have you ever licked the icing from the middle of a sandwich cookie?

• If so, then you’re using physical properties to identify the icing and separate it from the rest of the cookie

• You can use other physical properties to separate such as using a sifter to separate poppy seeds from sunflower seeds

• Or sand from iron fillings by using a magnet

Physical Change

• If you break a piece of gum, you change some of its physical properties—shape and size

• However, you haven’t changed the identity of the materials that make up the gum

• Each piece still tastes and chews the same

Physical Change

• A physical changephysical change is any change in size, shape, or state of matter

• These changes might involve energy changes, but the kind of substance—the identity of the element or compound—does not change!

Physical Change

So, does a change in state mean that a new substance has formed?

Physical Change to Separate

• I some parts of the world, water is very scarce, many such areas lie near the sea

• They obtain their drinking water by using the physical property of boiling point to separate the the salt from the water

• This process is called distillation• In distillation, you use an apparatus to

vaporize and condense liquid, leaving the solid material behind

Chemical Properties

• Have you ever seen the warning labels on paint thinners and lighter fluids that read “FLAMMABLE”

• Flammability is a chemical property

• Burning produces new substances during a chemical change