Physical and Chemical Properties and Changes

In your notebook: Describe the candle as completely as you can. List at least 10 descriptors of it.

Matter All objects are made of matter. Properties – Characteristic that describes matter.

General Properties Mass – Amount of matter Weight – Effect of Gravity on the matter Volume – How much space the matter takes up. Density – the amount of matter in a given volume. Movie

Density Density is the amount of matter in a given volume D = m/v Equal volumes of different substances have different masses. Equal masses of different substances have different volumes

Density Density is a property that can be used to identify an unknown substance. Density of water is 1 g/mL

An Example A geologist was doing some field work when he found a mineral that he could not identify. Density is one way it could be identified.

Example – Continued The sample has a mass of 75.3 g The volume of the sample is 15 cm3. What is its density? What mineral is it?

Example Continued Know mineral densities. Mineral D Calcite 2.7 Chalcopyrite 4.2 Pyrite 5.02 Galena 7.5

Specific Physical Properties Properties that describe the object’s appearance, smell, texture. I.e. color, texture, odor, taste, shape, hardness, volume, conductivity, density, phase, viscosity, malleability, ductility, luster, melting point (0ºC), boiling point (100ºC), etc

Physical Changes Changes in physical properties. It is still the same substance after the change. Cutting a piece of wood. It’s still wood. Compressing air. It’s still air. Changing states of matter

Chemical Properties Describe how the substance will react to form new substances. change in composition i.e. flammability, corrosion, pH, reactivity, inert.

Chemical Changes The process by which a substance changes to a new substance. Chemical Reactions – products have new sets of physical and chemical properties. Sodium – silver soft highly reactive metal. Chlorine – deadly poisonous gas. Sodium Chloride – tasty seasoning we eat on our food every day!

Physical or Chemical Property? Does it describe the substance? Does it describe how the substance will change in a chemical reaction?

Physical or Chemical Change? Is it still the same substance? Can I get it back? Is it a new substance? Does it have new physical and chemical properties?

Evidence of Chemical Reactions Color change Bubbles Change in Heat Endothermic – Feels cold Exothermic – Feels warm Precipitate formed

USING PROPERTIES

Properties are used to: Identify a new material Decide which properties to test Test sample (unknown) Compare results to known data Choose a material for a specific purpose Separate the substance in a mixture PHYSICAL: Filtration Distillation CHEMICAL: Flammability, reactivity, starch test