There is a reason for sig figs! Sig figs are used to represent how accurate the previous measurements are. You cannot do calculations with measurements that are less precise than the measuring device actually used. For example, if you were to use a ruler that measured to 1 decimal place (10 ticks between each inch mark), your measurement would have one decimal place determined by the scale and one decimal place that you estimated. Estimations are necessary because whether you estimate or not, there will still be error. Estimating provides less error than if you did not estimate. When using the numbers in calculations, you cannot have more decimal places than were in the original measurement for addition and subtraction. For multiplication and division, it depends on the lowest number of sig figs used (the least accurate measurement measured with the least accurate device).
Friday, November 11, 2011
Monday, September 19, 2011
Chemical vs. Physical Property At-Home Lab
Brandt Wood
Chemistry At- Home Lab
Object: Olive Oil
CHEMICAL PROPERTIES:
Chemical properties describe a substances ability to undergo a change in identity.
1. After mixing the 1oz of olive oil with 1tsp of bleach, the olive oil became very cloudy. Many small bubbles were formed inside. Some of the color was removed from the oil and bubbles were created, letting me know that a chemical reaction had taken place.
2. When I exposed the 1oz glass bowl of olive oil in a to ultra-violet light for 2 and one-half hours, the oil photo-oxidized and degraded. The chlorophyll in the olive oil was oxidized, taking away most of the green color that was in the oil and leaving it with a strong, gold color. The oxidation took place quickly, because photo oxidation can occur up to 30,000 times faster than auto-oxidation. I know that it is a chemical property because a change in color took place and chlorophyll is no longer as strong of an ingredient in the olive oil, making it a different substance.
3. After mixing 1tsp of hydrogen peroxide (H2O2) into the 1oz of olive oil, the oil became filled with small bubbles and the color was lightened, leaving it as a pale, yellow-green color. Due to the change in color and the formation of bubbles, I know that oxidation, a chemical reaction, took place.
CHEMICAL PROPERTIES (continued):
4. When I mixed 1 oz olive oil with 1 tsp. of mouthwash, the olive oil became a dark, slightly cloudy color and large light blue bubbles were formed in the oil. The color was changed and bubbles appeared in the oil, proving that a chemical reaction had taken place.
5. After I mixed 1 tsp. of dishwashing (liquid) soap with 1 oz. of olive oil, the soap and the oil separated. The majority of the mixture became a cloudy, light green color with white streaks going through it and small bubbles throughout, but the perimeter was the original yellow color. The color changed and bubbles were formed in the oil, telling me that a chemical reaction took place.
PHYSICAL PROPERTIES:
Physical Properties are characteristics that can be measured or observed without changing the substance’s identity.
1. Olive oil freezes at between 3°C and 4°C. When I put the 1 oz glass bowl of olive oil in the -18°C freezer, it solidified. The olive oil took on the feel of an ice cream type substance. Freezing point is defined as a physical property and can be observed and measured without changing the identity of the substance.
2. Olive oil boils at 299°C. Boiling point is defined as a physical property and can be observed and measured without changing the identity of the substance.
3. The viscosity of olive oil is 84cP. Viscosity is a physical property because it does not involve a change in substance and can be observed and measured without changing the identity of the object.
4. The density of olive oil is 920kg/m^3. Density is defined as a physical property and it can be observed and measured without changing the identity of the substance.
5. The smoking point of olive oil is 210°C. Smoking point is a physical property because it is the maximum temperature olive oil can reach BEFORE it forms a new substance. It can be observed or measured without the substance changing.
PHOTOGRAPHIC KEY:
PHOTOGRAPH OF RESULTS:
SOURCES:
Apostolos (Paul) K. Kiritsakis: Olive Oil, From the Tree to the Table, Second Edition
Apostolos (Paul) K. Kiritsakis: Olive Oil, From the Tree to the Table, Second Edition
Tous, J. and L. Ferguson. 1996. Mediterranean fruits. p. 416-430. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.
Nutritional composition of Mediterranean crops (per 100 g of edible portion). Source: Goulart (1980); Sawaya et al. (1983); Fernandez Diez (1983); IBPGR (1986); Morton (1987); Cantwell (1994).
Guido Costa: A great discussion of olive oil chemistry by Guido Costa in simple terms.
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