Classification of Matter Matter is made up of very tiny units called ...
Classification of Matter Matter is made up of very tiny units called atoms, of which we know about 114 types. Each type of atom is the building block of a different chemical element, thus there are 114 elements. 90% of all elements are natural and the remaining percentage of elements is those synthesized in the laboratories. When two or more elements are joined, they form a compound. A compound is made of many molecules. A molecule is the smallest entity having the same proportions of the constituent atoms as does the compound as a whole. An element and compounds are referred to as substances. When two or more substances mix, they form a mixture. When a mixture is uniform in composition and properties throughout, it is known as a homogeneous mixture or solution (e.g. ordinary air, seawater, and gasoline). When the composition and physical properties vary from one part of the mixture to another, it is known as a heterogeneous mixture (e.g. sand and water). Separating Mixtures Consider the mixture of sand and water being poured into a funnel lined with porous filter paper. The water passes through, but the sand is retained. This process of separation is known as filtration. On the other hand, we cannot filter a homogeneous mixture of copper (II) sulphate. However, this compound can be separated by boiling. This process is called distillation. States of Matter Matter generally exists in 3 states: solid, liquid, or gas. A solid contains atoms or molecules in close contact, sometimes in a highly organized arrangement called a crystal. As well, a solid had a definite shape. In a liquid, the atoms or molecules are usually further apart. The movement of these atoms/molecules give a liquid its most distinctive property: the ability to flow, covering the bottom and assume the shape of its container. In a gas, the distance between atoms/ molecules is much greater. A gas always expands to fill its container. ***In water, specifically ice, it is important to remember that liquid water is more dense than ice, since all the molecules in the liquid are joined tightly to each other to provide a sturdy framework for a block of ice.*** SI and Non-SI Units (Read 1.4) Density and Percent Composition When someone says a ton of bricks weigh more than a ton of cotton, they have the concepts of weight and density confused. Matter in a brick is more concentrated than in cotton, making bricks denser than cotton. Density is the ration of mass to volume. Density (d) = mass (m)/ volume (v). Mass and volume are extensive
properties. An extensive property is dependent on the quantity of matter observed, unless, the mass of the substance is divided by its volume. In this case, that is an intensive property. This is an independent of the amount of matter observed. (e.g. the density of water at 25ºC is the same whether it fills a small beaker or a large pool. Density is a function of temperature because volume varies with temperature, whereas mass remains constant. For example, as the average temperature of seawater increases, the seawater will become less dense and its volume will increase. Another factor that affects density is state of matter. Generally, solids are denser than liquids, and both are denser than gases. Density in Conversion Pathways 1. A cube of osmium 1.000 cm on edge weighs 22.48g. The density of osmium, therefore, is 22.48g/cm3. What would be the mass of a cube of osmium that is 1.25 in on edge (1 in = 2.54cm)? To solve this, we need to remember that V= l3. ? g osmium = [ 1.25 in. x (2.54 cm/ 1 in.)] 3x (22.48 g osmium/ 1 cm3) = 719 g osmium 2. At 25ºC the density of mercury is 13.5 g/mL. What is the volume, in mL, of 1.000 kg of mercury at 25ºC? ? mL mercury = 1.000 kg x (1000 g/ 1 kg) x (1 mL mercury/ 13.5 g) = 74.1 mL mercury (Also see example 1.2 and 1.3) Percent Composition 1. Currently, U.S. pennies are 2.40% copper and 97.60% zinc. What mass of each element is in a penny weighing 2.485g?
Consider 100 g of penny. Copper is (2.40 g copper/ 100 g penny) and zinc is (97.60g zinc/ 100g penny). (2.40 g copper/ 100 g penny) x 2.485 g penny = 0.0596 g copper (97.60 g zinc/ 100 g penny) x 2.485 g penny = 2.425 g zinc
2. A 75-g sample of sodium chloride is to be produced by evaporating to dryness a quantity of seawater containing 3.5 % sodium chloride by mass.
How many liters of seawater must be taken for this purpose? Assume a density of 1.03 g/ mL for seawater.
? L seawater = 75 g sodium chloride x (100 g seawater / 3.5 g sodium chloride) x (1 mL seawater / 1.03 g seawater) x (1 L seawater / 1000 mL seawater) = 2.1 L seawater
Uncertainties in Scientific Measurement Precision refers to how well a number or independent measurement agrees with one another. Accuracy refers to how close to the true value a given measurement is (e.g. a bathroom scale is neither accurate nor precise, a lab balance is fairly accurate but not very precise, but an analytical balance is both accurate and precise). Significant Figures Consider:
0
.
Not significant: zeros used only to locate the decimal point.
0
Not significant: zero used for cosmetic
0
Significant: zeros at the end of a number to the right of decimal point.
Significant: all zeros between
4
0
0
4
5
0
0
Significant: all non-zeros integers
Rounding Rules 1. If the first digit you remove is less than 5, round down by dropping it and all following digits. Example: 5.664525 = 5.66
2. If the first digit you remove 6 or greater, round up by adding 1 to the digit on the left. Example: 5.664525 = 5.7 3. If the first digit you remove is 5 and there are more non-zero digits following, round up. Example: 5.664525 = 5.665 4. If the digit you remove is a 5 with nothing following, round down. Example: 5.664525 = 5.66452 Adding and Subtracting Rules -the result must be expressed with the same number of digits beyond the decimal point as the quantity carrying the smallest number of such digits. Example: 15.02 g + 9986.0 g + 3.518 g = 10 004. 538 g ***There are two situations where a quantity may be exact (not subjected to any errors in the calculation). This may occur: by definition (e.g. 1 min = 60 sec or 1 in = 2.54 cm) and by counting (e.g. a cube has 6 faces or two hydrogen atoms in a water molecule).***
properties. An extensive property is dependent on the quantity of matter observed, unless, the mass of the substance is divided by its volume. In this case, that is an intensive property. This is an independent of the amount of matter observed. (e.g. the density of water at 25ºC is the same whether it fills a small beaker or a large pool. Density is a function of temperature because volume varies with temperature, whereas mass remains constant. For example, as the average temperature of seawater increases, the seawater will become less dense and its volume will increase. Another factor that affects density is state of matter. Generally, solids are denser than liquids, and both are denser than gases. Density in Conversion Pathways 1. A cube of osmium 1.000 cm on edge weighs 22.48g. The density of osmium, therefore, is 22.48g/cm3. What would be the mass of a cube of osmium that is 1.25 in on edge (1 in = 2.54cm)? To solve this, we need to remember that V= l3. ? g osmium = [ 1.25 in. x (2.54 cm/ 1 in.)] 3x (22.48 g osmium/ 1 cm3) = 719 g osmium 2. At 25ºC the density of mercury is 13.5 g/mL. What is the volume, in mL, of 1.000 kg of mercury at 25ºC? ? mL mercury = 1.000 kg x (1000 g/ 1 kg) x (1 mL mercury/ 13.5 g) = 74.1 mL mercury (Also see example 1.2 and 1.3) Percent Composition 1. Currently, U.S. pennies are 2.40% copper and 97.60% zinc. What mass of each element is in a penny weighing 2.485g?
Consider 100 g of penny. Copper is (2.40 g copper/ 100 g penny) and zinc is (97.60g zinc/ 100g penny). (2.40 g copper/ 100 g penny) x 2.485 g penny = 0.0596 g copper (97.60 g zinc/ 100 g penny) x 2.485 g penny = 2.425 g zinc
2. A 75-g sample of sodium chloride is to be produced by evaporating to dryness a quantity of seawater containing 3.5 % sodium chloride by mass.
How many liters of seawater must be taken for this purpose? Assume a density of 1.03 g/ mL for seawater.
? L seawater = 75 g sodium chloride x (100 g seawater / 3.5 g sodium chloride) x (1 mL seawater / 1.03 g seawater) x (1 L seawater / 1000 mL seawater) = 2.1 L seawater
Uncertainties in Scientific Measurement Precision refers to how well a number or independent measurement agrees with one another. Accuracy refers to how close to the true value a given measurement is (e.g. a bathroom scale is neither accurate nor precise, a lab balance is fairly accurate but not very precise, but an analytical balance is both accurate and precise). Significant Figures Consider:
0
.
Not significant: zeros used only to locate the decimal point.
0
Not significant: zero used for cosmetic
0
Significant: zeros at the end of a number to the right of decimal point.
Significant: all zeros between
4
0
0
4
5
0
0
Significant: all non-zeros integers
Rounding Rules 1. If the first digit you remove is less than 5, round down by dropping it and all following digits. Example: 5.664525 = 5.66
2. If the first digit you remove 6 or greater, round up by adding 1 to the digit on the left. Example: 5.664525 = 5.7 3. If the first digit you remove is 5 and there are more non-zero digits following, round up. Example: 5.664525 = 5.665 4. If the digit you remove is a 5 with nothing following, round down. Example: 5.664525 = 5.66452 Adding and Subtracting Rules -the result must be expressed with the same number of digits beyond the decimal point as the quantity carrying the smallest number of such digits. Example: 15.02 g + 9986.0 g + 3.518 g = 10 004. 538 g ***There are two situations where a quantity may be exact (not subjected to any errors in the calculation). This may occur: by definition (e.g. 1 min = 60 sec or 1 in = 2.54 cm) and by counting (e.g. a cube has 6 faces or two hydrogen atoms in a water molecule).***
