Properties of Matter
Investigation 4 – Concept Day
Properties of Matter: Investigation 4
- This final Investigation of the CELL Properties of Matter concludes with experiments involving another chemical property of matter, pH.
- pH is used to describe whether a compound is an acid, base, or neutral,
- the range of the pH scale is from 0 to 14,
- substances with a pH below 7 are called acidic,
- substances with a pH above 7 are called basic, and
- substances with a pH of 7 are called neutral.
- This slide depicts the pH Scale and highlights the pH of a number of common compounds that you may be familiar with.
Note: It is interesting to note that blood, saliva, tears, and other body fluids are near neutral as is the pH of seawater. As life on Earth likely originated in the sea, perhaps this is not a coincidence.
Note: This slide shows the proper protection to use when working in the lab. Goggles and safety glasses, and other lab protection like gloves and masks, do no good if not used properly.
- You should avoid touching your eyes or other body areas while wearing safety gloves.
- Wash your hands after removing safety gloves to remove any talcum powder that might cause irritation.
This slide illustrates two common methods of determining the pH of a solution:
- The pH meter on the left is found in nearly all commercial and research labs. pH readings using this type of instrument are both accurate and fast.
- pH paper on the right is less expensive than pH meters and is much easier to maintain.
Note: A pH strip is dipped into a solution and then the resultant color is compared to a reference guide as shown in this slide. Sometimes, when the color of the activated strip appears to be between two colors on the guide, you may report the pH as something like 5.5. While our pH readings in this Investigation do not require extreme accuracy, keep in mind that a reported reading of 5.5 really just means “more than 5 and less than 6”.
This final slide lists some of the highlights of the CELL Properties of Matter. It can serve as a background for any number of discussions at the end of this CELL or as a review for you at a later time.