Chemical vs physical change
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Chemical vs. Physical Change - PowerPoint PPT Presentation

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Chemical vs. Physical Change. Physical Change. Any process involving a substance changing from one state of matter to another without altering the chemical composition. These changes are often considered ‘easy’ to undo. Ex. Ice melting, water boiling, sugar dissolving. PhysicalChange1_Part1.

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Physical change
Physical Change

  • Any process involving a substance changing from one state of matter to another without altering the chemical composition.

  • These changes are often considered ‘easy’ to undo.

  • Ex. Ice melting, water boiling, sugar dissolving.



Chemical change
Chemical Change

A change that occurs when one or more substances are changed into a new substance.

These changes cannot be reversed.

Some observations that occur during a chemical change are: color, fizzing, precipitate (solids forming), heat change (hot or cold).



Acids bases
Acids & Bases

  • Acids are compounds which produce hydrogen ions when combined with water.

    • Hydrogen ions have an overall positive charge (H+)

  • Bases are compounds that produce hydroxide ions when combined with water.

    • Hydroxide ions have an overall negative charge (OH-)

The ph scale
The pH scale

  • Substances that are acids or bases can be measured on a scale from 0 to 14.

  • This scale is called the pH scale.

  • “pH” stands for ‘potential hydrogen’

  • Acids have a pH less than 7

  • Bases have a pH higher than 7.

Turning blue black
Turning Blue/Black

  • Iodine solution contains iodine, potassium iodide, water, and alcohol.

  • This is a good indicator for starch molecules.

  • When combined with starch molecules it will turn blue in color.

  • This is due to a chemical change between the starch and iodine atoms.

Turning pink orange green
Turning Pink/Orange/Green

  • This is also a chemical change.

  • Many fruits or vegetables contain pigments which will change color when added to an acid or base.

  • These pigments will change color as their molecules change.

Bubbling fizzing

  • Bubbling or fizzing is also a chemical change.

  • Bubbles are a result of the formation of Carbon Dioxide.

  • Carbon Dioxide is formed when molecules recombine to form a new substance. Often times carbon dioxide is left over and given off as a gas.

The crystal lab
The Crystal Lab

  • You will be investigating several crystals by examining their physical properties.

  • You will utilize your results to try to identify an ‘unknown’ crystal.

Crystal size
Crystal - Size

  • Crystal size is determined by many variables. These can include:

    • Time of formation

    • Amount of substance

    • Rate of evaporation

      (Typically, the more time, amount of substance, and slower rate….. The larger the crystals will be.)

Crystal color
Crystal - Color

  • The color of a crystal is determined by the substance and the elements which are found in the substance.

  • Each crystal of the same substance should have a similar color although variations may exist.

Crystal shape
Crystal - Shape

  • The Shape of a crystal is determined by the atomic structure of the substance in the crystal.

  • There are some common crystalline structures that are often seen in the natural world. They include…..

    • Cubic/Hexagonal/Triclinic/Monoclinic/ Orthorhombic/Rhomobohedral/ Tetragonal

Crystal luster
Crystal - Luster

  • Luster describes how light reflects off the surface of a crystal.

  • Terms to describe luster:

    • Glossy

    • Metallic

    • Dull

    • Pearly

    • Silky

Crystal light transmission
Crystal – Light Transmission

  • Light Transmission is used to describe how light passes through a crystal.

  • Terms used to describe light transmission include:

    • Translucent/Transparent/Opaque

A sense ational activity

Lab activity

A Sense-ational Activity

In the Sense-ational Activity you will be conducting an experiment to test your skills of observation.

In the first part of this experiment, you will be observing 5 white powders with each of you senses.

In the second part of this experiment, you will be observing how each of these powders reacts (chemically / physically) when mixed with various solutions.

Your ability to observe with all of your senses will be tested.

Powder a
Powder ‘A’

  • Powder A was cornstarch.

  • Corn starch is an agent used as a thickener.

  • It is composed of longer starch molecules and has a neutral pH.

Powder b
Powder ‘B’

  • Powder B was Baking Soda (sodium bicarbonate)

  • Baking soda is used to generate bubbles in recipes that contain acidic ingredients.

  • This is a weak base.

Powder c
Powder ‘C’

  • Powder C was Cream of Tartar

  • Cream of Tartar is used to prevent sugar from crystallizing during the making of candy.

  • It is acidic.

Powder d
Powder ‘D’

  • Powder D was powdered sugar.

  • Powdered sugar is made of smaller sucrose molecules.

Powder e
Powder ‘E’

  • Powder E was baking powder (combination of baking soda and calcium acid phosphate and corn starch)

  • This will cause bubbles whether or not other ingredients are acidic.