Physical Properties of Two Types of Solids
The purpose of this lab is to study some of the physical properties of two types of solids – ionic and molecular. 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. 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.
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.
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.
- sodium chloride
- filter paper
- watch glass
- crucible cover
- clay triangle
- iron ring
- ring stand
- 150mm test tubes (4)
- 10mL graduated cylinder
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...