12.1 Properties of Solids Different kinds of matter have different characteristics. Characteristics that can you observe directly are called physical properties. Physical properties include color, texture, density, brittleness, and state (solid, liquid, or gas). Ex. Iron is solid at room temp.

12.1 Properties of Solids A physical change is any change in the size, shape, or phase of matter in which the identity of a substance does not change. For example, when water is frozen, it changes from a liquid to a solid.

12.1 Properties of Solids Properties that can only be observed when one substance changes into a different substance are called chemical properties. Any change that transforms one substance into a different substance is called a chemical change. Ex. If you leave a nail outside, it rusts.

2.2 Density Density describes how much mass is in a given volume of a material.

12.1 Properties of Solids The density of a solid material depends on two things: the individual mass of each atom or molecule, how closely the atoms or molecules are packed together. Carbon atoms in diamond are packed very tightly.

12.1 Properties of Solids Paraffin wax is also mostly carbon, but its density is only 0.87 g/cm3. Paraffin’s carbon atoms are mixed with hydrogen atoms in long molecules that take up more space. The density of paraffin is low compared to diamond

2.2 Density Solids, liquids and gases are matter, so they all have density. The density of water is about one gram per cubic centimeter.

2.2 Density of common materials Density is a property of material independent of quantity or shape.

2.2 Density The units used for density depend on whether the substance is solid or liquid. For liquids use units of grams per milliliter (g/mL) For solids use density in units of g/cm3 or kg/m3.

2.2 Density of common materials Liquids tend to be less dense than solids of the same material. Ex. solder (“sodder)

2.2 Density of common materials Water is an exception to this rule. The density of solid water (ice) is less than the density of liquid water.

2.2 Determining Density To find the density of a material, you need to know the mass and volume of a solid sample of the material. Mass is measured with a balance or scale. Use the displacement method or calculate the volume.

Calculating Density Looking for: Given: Relationship: Solution: Solving Problems Calculating Density Looking for: …the density of the candle Given: …mass = 15.0 g; volume = 17.0 mL Relationship: D = m/V Solution: 15.0 g ÷ 17.0 mL = 0.8823529 g/mL # Sig. fig = .882 g/mL

12.1 Mechanical properties “Strength” describes the ability of a solid object to maintain its shape even when force is applied.

12.1 Mechanical properties Tensile strength is a measure of how much stress a material can withstand before breaking.

12.1 Mechanical properties Hardness measures a solid’s resistance to scratching. How might you compare the hardness of these two metals?

12.1 Mechanical properties Elasticity describes a solid’s ability to be stretched and then return to its original size. Brittleness is defined as the tendency of a solid to crack or break before stretching very much.

12.1 Mechanical properties A ductile material can be bent a relatively large amount without breaking. The ductility of many metals, like copper, allow then to be drawn into wire.

12.1 Mechanical properties Malleability measures a solid’s ability to be pounded into thin sheets. Aluminum is a highly malleable metal.