Properties Properties of matter are like characteristics. By observing them and measuring them, we can use them to describe matter. There are two types of properties – physical and chemical. Physical Properties: properties that can be observed directly or measured without changing the chemical identity of the substance Ex. Mass, volume, shape, size, color, luster, hardness, etc.

A few you may not know about… Physical Properties A few you may not know about… Melting point: temperature at which a solid becomes a liquid Boiling point: temperature at which a liquid becomes a gas

A few you may not know about… Physical Properties A few you may not know about… Viscosity: a fluid’s resistance to flow A physical property only of liquids Can change with temperature Think “how thick it is” Ex. Viscosity of syrup is high and of water is low

A few you may not know about… Physical Properties A few you may not know about… Solubility: a measure of how well a solute dissolves in a solvent Solute = what is being dissolved (Ex. Lemonade powder) Solvent = what is doing the dissolving (Ex. Water) Solution = the result (Ex. Lemonade)

Physical Properties A few you may not know about… Density: measure of compactness or consistency of a material Mass per unit of volume Measured in g/cm3 or g/mL Density doesn’t change, regardless of size Density = mass volume Mass is measured in grams (g), using a scale Volume is measured in mL or cm3, using 2 different methods

Finding volume to calculate density Volume of a solid: if a regular shape, use a ruler and the appropriate geometric equation Cube or rectangular prism: V = l x w x h Cylinder: V = π r2 h Measured in cm3

Example #1 What is the density of a 15 g box measuring 10 cm by 5 cm by 2 cm? d = ? m = 15 g v = ? d = m v v = l x w x h v = l x w x h v = 10 x 5 x 2 v = 100 cm3 d = m v d = 15 100 d = 0.15 g/cm3

Finding volume to calculate density Volume of a liquid: if a liquid or an irregularly shaped solid, use a graduated cylinder (and water displacement for a solid) Measured in mL Water Displacement: Put enough water in graduated cylinder to cover the object. Record initial volume. Add object. Record final volume, with object in it. Subtract Vf – Vi to find the volume of the object. Note: Water has a density of about 1 g/mL, so anything with a density less than 1 will float when placed in water, anything with a density more than 1 will sink when placed in water. This should be something they observe/pick up from the density lab, but I just like to emphasize that here, especially for honors students.

Example #2 d = ? m = 8.1 g v = ? d = m v v = vf - vi v = vf - vi A sample of aluminum is put into 10.5 mL of water. If the water rises to 13.5 mL when the aluminum is added, what is the density of the aluminum if it has a mass of 8.1 g? d = ? m = 8.1 g v = ? d = m v v = vf - vi v = vf - vi v = 13.5 – 10.5 v = 3 mL d = m v d = 8.1 3 d = 2.7 g/mL

Chemical Properties Chemical Properties: properties that can only be observed or measured by changing the chemical identity of a substance. By observing it a new substance is formed Ex. Toxicity, flammability, combustibility, radioactivity, etc.

A few you may not know about… Chemical Properties A few you may not know about… Combustibility: how easily a substance will set on fire Ex. Burning charcoal Reactivity: how easily a substance reacts, usually with an acid or base Ex. Fluorine gas is highly reactive and will spontaneously ignite a concrete block at room temperature Oxidation: how easily a substance reacts with oxygen Ex. Iron reacts with oxygen and moisture to create rust

Physical and Chemical Changes Matter can undergo both physical and chemical changes. Physical Change: a change in a substance that only affects its physical properties Ex. Cutting, coloring, crushing, melting, boiling, etc. Chemical Change: a change in a substance that affects its chemical properties thus a chemical reaction occurs and a new substance is formed Ex. Burning, rusting, decomposing, etc. Chemical Reaction: process by which the atoms of one or more substances are rearranged to form different substances

Law of Conservation of Matter Matter is neither created or destroyed during a chemical change. It only changes forms. Mass cannot be “lost”, even when a chemical reaction happens.

Evidence of a Chemical Change Signs that a chemical change has occurred, resulting in a chemical reaction include: Release of light Temperature change Odor change Sudden color change Gas given off Sudden appearance of a solid (called a precipitate)