Reviewing MATTER

 Matter: anything that has mass and takes up space  Mass – the amount of matter in something  Volume – the amount of space something occupies  Which of the following is matter?

   A car?

A box?

You?

What is a property?

 Property: a characteristic of a substance that can be observed

Physical Property

Physical property: a property that can be observed without changing the identity of the substance.

Examples: • luster • melting point • malleability: the ability to be hammered into a thin sheet • ductility: the ability to be stretched into a wire • • boiling point density • solubility • specific heat

Additional Physical Properties… EXTENSIVE PROPERTY Depends on the amount of matter.

Example – Length, mass, volume, weight

INTENSIVE PROPERTY

Does not depend on the amount of matter.

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Example – Color, density, hardness, ductility, malleability, odor, melting/ boiling point

Special Physical Properties

 Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure water = 0 o C

Special Physical Properties

 Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure water = 100 o C

Density

  Density is the amount of mass per unit of volume.

Since density is an intensive property, it can be used to identify a substance.

Density

  The density of water is 1.0g/mL If a substance has a density higher than 1 it will sink in water, less than 1 it will float in water.

Density Calculations

 Calculations: Density = mass = g/mL = g/cm 3 Volume Units are grams/ml or grams/cm3 where mass is measured in grams and volume is measured in ml or cm3

Density Calculations

 A cube has a mass of 2.8 g and occupies a volume of 3.67 ml. Would this object float or sink in water?

Mass = 2.8 g Volume = 3.67 mL D = 2.8g/3.67 mL= 0.76 g/mL This object would float in water because its density is less than water (1.0 g/mL).

Chemical Properties

 Chemical property: a property that can only be observed by changing the identity of the substance Examples: •Flammability: ability to burn •Ability to rust •reactivity with vinegar

PHYSICAL & CHEMICAL CHANGES

Changes in matter

  Change: the act of altering a substance In science, we talk of two types of changes: physical chemical

Physical Change

 Physical change: a change that occurs that does not change the identity or make up of the substance  Melting ice (change in state or phase)    Freezing Kool-aid Tearing paper Boiling water (same as melting)

Physical Changes

 Physical changes are changes that alter the size, shape, location or physical state of a substance but not its chemical state.

Here’s An Example…

  A physical change in a substance doesn't change what the substance is.

cutting paper –  physical change in the shape and size of the paper. 

It is still paper!!!!!!

So What Does That All Mean?

 If the substance is still the same substance after it has been changed…   It’s a Physical Change.

Example… Boiling water  Boiling Water becomes Water vapor Water = water

     What Other Kinds of Changes Are Physical?

Cutting Tearing Shredding   Change in Phase Relocating Shrinking  Dissolving Enlarging  Rotating  Molding (shaping)

Under certain conditions, a substance can change from any one state of matter another. Changes of state are

physical changes

.

Wood cut down into logs is a physical change

Chemical Changes

  Chemical change: a change that occurs causing the identity of the substance to change    Burning Digesting food Reacting with other substances A chemical change is also called a

chemical reaction

Chemical Changes

 Chemical changes are changes that alter the chemical make up of the substance being changed.

Chemical Changes

 If you end up with a chemical or chemicals that you did not start with. . .  It is a chemical change!!!!!!!

Chemical Changes

 A new substance is formed with new and different properties.

 A chemical change is not easily reversed.

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Signs That a Chemical Change has occurred

Creation of a gas (bubbles) Creation or loss of heat Fire Rotting Breaking down (decomposition) Precipitation (Sour milk clumps) Cooking Rusting (oxidation)

The strike of a match is a chemical change due to the reaction of the chemicals with oxygen.

Burning woods turns to charcoal and ashes. This is a chemical change .

Is it Physical or Chemical?

Chemical Change

Melting cheese Burning wood Milk souring Folding up paper Bicycle rusting

Physical

 Start physical changes challenge Powerpoint

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Chemical Reactions are…

When one or more substances are changed into new substances.

 Reactants - the stuff you start with  Products - what you make  The products will have NEW PROPERTIES different from the reactants you started with  Arrow points from the reactants

to

the new products

Plants make chlorophyll in the plants leaves.

The color changes in autumn leaves are due, in part, to the ending of a chemical reaction. The plants stop making chlorophyll while existing chlorophyll is breaking down. The brilliant colors of fall foliage result when green chlorophyll in leaves breaks down. The colors of other substances in the leaves become visible.

The copper-covered Statue of Liberty has stood in upper New York Bay for more than a 100 years. The green color of the Statue of Liberty comes from a change to the statues copper metal covering. These changes are a result from chemical reactions.

Conservation of Mass

 During any chemical reaction, the mass of the products is always equal to the mass of the reactants.

 All the mass can be accounted for:  Burning of wood results in products that appear to have less mass as ashes; where is the rest?

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Law of conservation of mass

Matter changes whenever energy is added or taken away. In every physical and chemical change, the total amount of energy stays the same. This principle is called the Law of Conservation of Energy.