Two Types of Solids Essay

March 2, 2011 Lab Report Physical Properties of Two Types of Solids SCH3U0 Maggie Liu Abstract The purpose of this lab is to study some of the physical properties of two types of solids – ionic and molecular - Two Types of Solids Essay introduction. The samples used are sodium chloride (ionic) and camphor (molecular). The physical properties studied are odour, hardness, melting point, solubility in water and solubility in 2-propanol.

It is observed that some of the physical properties of sodium chloride are no odours, hard, a high melting point, soluble in water and insoluble in 2-propanol; some of the physical properties of camphor are a strong odour, soft, a low melting point, insoluble in water and soluble in 2-propanol. A few conclusions can be drawn from these observations. The particles in ionic solids are held tightly by the force of attraction between ions with opposite charge, because of this strong force of attraction of positive and negative, ionic solids tend to have no odours, a high melting point and they are hard.

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The particles in molecular solids are held by the van der Waals force of attraction, because of this relatively weak force of attraction, molecular solids have a strong odour, a low melting point and they are soft. Sodium chloride dissolving in only water (not in 2-propanol) and camphor dissolving in only 2-propanol (not in water) have proved that polar solids are soluble in polar liquids only, and non-polar solids are soluble in non-polar liquids only. Introduction

Ionic solids form as a result of the chemical reaction between metals and non-metals. Atoms that become positively charged by losing electrons are called cation; atoms that become negatively charge by gaining electrons are called anion. During the formation of ionic solids, a few electrons from the metals are transferred completely to the non-metals. The attraction between ions of opposite charge is what virtually holds the particles in ionic solids together. The other type of solids is molecular solids.

In molecular solids, atoms of molecules are held together by covalent bonds. Molecular solids are the products of the chemical reaction between non-metals only. Each type of solid has its distinct physical properties. In this experiment, four physical properties of an ionic solid and a molecular solid will be examined and studied – odour, hardness, melting point and solubility. The solids used in this lab are sodium chloride which contains sodium and chlorine, and camphor which contains carbon, hydrogen and oxygen. Hypothesis

Because sodium chloride is an ionic solid, it will have no odours, a high melting point and it will be hard. Sodium chloride will be soluble in water only (not in 2-propanol), for it is polar. Because camphor is a molecular solid, it will have a strong odour, a low melting point and it will be soft. Camphor will be soluble in 2-propanol only (not in water), for it is non-polar. Materials – sodium chloride – camphor – 2-propanol – water Apparatus – filter paper – watch glass – crucible cover – clay triangle – iron ring – ring stand – burner scoopula – 150mm test tubes (4) – 10mL graduated cylinder Experimental Procedure 1. Placed samples of sodium chloride and camphor separately on a piece of filter paper to observe the odour of each solid. 2. Rubbed a small sample of each solid between fingers to feel whether it is soft or hard. 3. Placed a few crystals of sodium chloride on an inverted crucible cover. Set up the apparatus used for heating. Put the crucible cover on a clay triangle on an iron ring and heated it gently. Repeated the same process of heating for camphor.

Noted the observations for each solid 4. Divided the remaining sodium chloride evenly into two test tubes, and the remaining camphor into two other test tubes. Added 3 ml of water to one test tube containing sodium chloride and one test tube containing camphor; shook it vigorously with care. Added 3ml of 2-propanol to the remaining test tube containing sodium chloride and the remaining test tube containing camphor; shook it vigorously with care. Noted the observations for each solid in both water and 2-propanol. Observations Physical property |Sodium chloride |camphor | |Odour |No odour |Strong (mint) | |Hardness |hard |soft | |Melting point |high |low | |Solubility in water |soluble |insoluble | |Solubility in 2-propanol |insoluble |soluble | Sodium chloride does not have any odours, whereas camphor has a strong mint-like smell. It is found that ionic compounds usually do not have odours because they are solids and the particles are all held tightly which makes the gas nearly impossible to be released into air and make the smell, however, many molecular solids do have odours because their particles are ot held very tightly and there is space between the particles. Vapor or gas can be produced and released into air which causes smell. Sodium chloride is harder than camphor. It is found that ionic solids tend to be hard because of the strong force of attraction between ions of opposite charge. The particles are all in fixed positions. Molecular solids are generally soft because the force of attraction between the particles within the solid is weak. Sodium Chloride has a higher melting point than camphor. It is found that ionic solids usually have a high melting point, for it takes a lot of energy to break the attraction (bond) between ions of opposite charge.

In covalent bonding, atoms simply share electrons and it takes less energy to break the bonding of molecular solids. Sodium Chloride is soluble in water, but not in 2-propanol. There are not big enough attractions between the 2-propanol molecules and the ions that can overcome the strong attraction held within the solid. Camphor is not soluble in water, but it dissolves in 2-propanol. Analysis 1. Sodium Chloride is the ionic solid. The electronegativity of sodium is 0. 93, and the electronegativity of chlorine is 3. 16. The difference is 2. 23. This difference is greater than 1. 7 which means sodium chloride is an ionic solid. 2. A strong smell indicates that the particles in a solid can leave its surface easily.

The particles are not held tightly within the solid, and there is much space between the particles which makes it easier for the particles to travel within the solid and leave the surface. When many particles are released into the air, a strong odour can be sensed. 3. Ionic solids have the stronger forces of attraction. Ionic solids are formed when metals give electrons to non-metals; what holds all the particles tightly is this strong force of attraction between ions of opposite charge (The sample used in this lab is sodium chloride in which the electron that sodium gives up is transferred to chlorine; they have the opposite charge: 1+/1-). Molecular solids don’t have a very strong force of attraction because the relationship of atoms is merely sharing electrons.

The strong odour of molecular solids also indicates that the force of attraction is relatively weak which allows gas to be produced, released into the air and cause the smell. 4. The strength of attractions between ions of opposite charge is stronger than the strength of van der Waals forces of attraction. It takes a lot of energy to overcome the strong bond, the strong force of attraction between ions of opposite charge, and that is why ionic solids have a high melting point. This strong force of attraction also holds all the particles in ionic solids in fixed positions, and that is why ionic solids tend to be hard. The strength of van der Waals forces of attraction is not very strong. Molecular solids have a low melting point because the weak bond takes less energy to break.

Molecular solids are usually soft, for the strength of van der Waals forces of attraction is not that strong and can not hold all the particles in fixed positions. 5. Sodium chloride is a polar solid, whereas camphor is a non-polar solid. There are two kinds of liquid here – water which is polar and 2-propanol which is non-polar. Polar solids will only dissolve in polar liquids, and non-polar solids are only soluble in non-polar liquids. As a result, sodium chloride is only soluble in water and camphor is only soluble in 2-propanol. Conclusion The purpose of this lab is to examine and study some of the physical properties of two types of solids – ionic and molecular. The samples used are sodium chloride (ionic) and camphor (molecular).

Based on the observations, some of the physical properties of sodium chloride are no odours, hard, a high melting point, soluble in water and insoluble in 2-propanol; some of the physical properties of camphor are a strong odour, soft, a low melting point, insoluble in water and soluble in 2-propanol. Conclusions are drawn from these observations. Because of the strong force of attraction between ions with opposite charge, ionic solids tend to have no odours, a high melting point and they are hard. Due to the relatively weak van der Waals force of attraction, molecular solids usually have strong odours, a low melting point and they are soft. Sodium chloride dissolving in only water (not in 2-propanol) and camphor dissolving in only 2-propanol (not in water) have proved that polar solids are soluble in polar liquids only, and non-polar solids are soluble in non-polar liquids only.

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