Significant Figure Rules and Accuracy vs. Precision Unit 1

Significant Figure Rules In any calculation, your answer cannot have more digits than the measurement with the least amount of digits given All nonzero numbers are always significant (1,2,3,4,5,6,7,8,9) Zeroes between two nonzero numbers are always significant (505 has 3 significant figures) Zeroes at the end of a number that contains a decimal are significant (21,000. has 5 significant figures, 432.50 has 5 significant figures) Leading zeroes are never significant (0.0052 has two significant figures) Zeroes at the end of a number without a decimal are not significant (300 has 1 significant figure)

Accuracy vs. Precision Accuracy is a measure of how close a result comes to the accepted answer. Precision is a measure of how close together several results are to each other.

Mixtures A mixture is a physical blend of two or more substances This means the parts are not bonded together, therefore bonds must not be broken to separate them

Homogeneous vs. Heterogeneous 2 types of mixtures: Homogeneous and Heterogeneous Homogeneous—the composition is the same throughout (also known as a solution) Examples: Salt water, vinegar, stainless steel (mixture of iron, chromium, and nickel) Heterogeneous—the composition is not the same throughout Examples: Oil and water, ice water, chicken noodle soup

Separating Mixtures Because they are not bonded together, separating mixtures does not require breaking bonds Separating a mixture is a physical change Heterogeneous mixtures are typically easier to separate Filtration—process that separates a solid from a liquid in a heterogeneous mixture

Separating Mixtures Separating a homogeneous mixture, though, requires manipulating the physical properties of the components of the mixture Physical properties used to separate mixtures include: boiling point, freezing point, and melting point Distillation is the process of separating mixtures based on differences in boiling point