Physical Properties p. 10 – 15 Chapter 1 Section 2 Vocabulary: physical property density physical change

Physical Properties A physical property of matter can be observed or measured without changing the matter’s identity. Gathering information about the matter by identifying its color, odor, mass or volume do not change the property of the matter. For example, you don’t have to change an apple’s identity to see its color or measure its volume. Other physical properties, such as magnetism, the ability to conduct an electric current, strength, and flexibility, can help someone identify how to use a substance

Examples of Physical Properties Physical Property: a characteristic of a substance that does not involve a chemical change, such as density, color or hardness

Density Density is a physical property that describes the relationship between mass (g) and volume (mL). Density is the amount of matter in a given space (or how much stuff can be crammed into a specific amount of space). A golf ball and a ping pong ball have similar volumes, but a golf ball has more than mass than a ping pong ball does. So, the golf ball has a greater density.

Liquid Layers The graduated cylinder contains six liquids. From the top to the bottom they are: corn oil, water, shampoo, dish detergent, antifreeze, and maple syrup. They can form six layers because of the differences in density. The densest layer is on the bottom and the least dense layer is on the top. The order of the layers shows the order of increasing density.

The cotton balls and the tomatoes have the same mass, but the cotton is much less dense than the tomatoes. The tomatoes would be less awkward to carry around than the cotton balls. The cotton balls are much less dense than the tomatoes, so it takes a lot of cotton balls to equal the mass of the tomatoes. Knowing the density of a substance can also tell you if the substance will float or sink in water. If the density of an object is less dense than the density of water the object will float. Likewise, a solid object whose density is greater than the density of water will sink when the object is placed in water.

Solving for Density To find an object’s density (D), first measure the mass (m) using a balance scale. Then find the volume (V) using a graduated cylinder, L X W X H formula, or displacement method. Then use the following equation to solve for density: m Think of the following to remember the D = V formula for finding density… Density LOVES mass and Volume: D = Can you see the m at the top of the heart? Can you see the V at the bottom of the heart? Units for density consist of a mass unit divided by a volume unit. Some units for density are g/cm³ and g/mL. The volume of a solid is given in cubic centimeters and the volume of a liquid is given in mL.

Using Density to Identify Substances Density is a useful property for identifying substances. Each substance has a density that is different from the density of other substances. The density of a substance is always the same at a given temperature and pressure. Take a look at the densities of several common substances… Substance Density (g/cm³) Helium (gas) 0.0001663 Zinc (solid) 7.13 Oxygen (gas) 0.001331 Silver (solid) 10.50 Water (liquid) 1.00 Lead (solid) 11.35 Pyrite (solid) 5.02 Mercury (liquid) 13.55

Physical Changes DO NOT Form New Substances! A physical change is a change that affects one or more physical properties of a substance without changing any chemical properties. Imagine that a piece of silver is pounded and molded into a heart shaped pendant. The change is a physical one because only the shape of the silver has changed. The piece of silver is still silver. Its properties are still the same.

Examples of Physical Change Freezing water to make ice cubes and sanding a piece of wood are examples of physical changes. These changes do not change the identities of the substances. Ice is still water and sawdust is still wood. Another interesting physical change takes place when certain substances dissolve in other substances. For example, when you dissolve sugar in water, the sugar seems to disappear. If you heat the mixture, the water evaporates and you will have the sugar left at the bottom of the cup, proving that the sugar is still there. The sugar went through a physical change when it dissolved.

= Matter and Physical Changes Physical changes DO NOT change the identity of the matter involved. = If you make a figure from a lump of clay, you change the clay’s shape and cause a physical change. but the identity of the clay does not change. The properties of the figure are the same as those of the lump of clay.

The Physical Changes Song

Quiz Time! 1. Name four physical properties. color, shape, odor, mass, volume, texture, state, density, thermal conductivity, malleability, ductility, solubility 2. What will happen to an object placed in water if the object’s density is less than water’s density? It will float 3. You have two objects, both a bout the size of an orange. Object A has a mass of 1,487g, and Object B has a mass of 878g. Which has the greater density? Why? Both objects have the same volume (size of an orange), so the object with more mass has the greater density.

4. What is a physical change? a change that occurs to a substance or object and that does not change the identity of the substance 5. The units of density for a rectangular piece of wood are: A. g/mm B. cubic cm C. kg/L D. g/cm³ D 6. Name six physical changes that matter can go through. breaking, melting, freezing, cutting, crushing, dissolving