Matter – Properties & Changes Chapter 5 Matter – Properties & Changes

Ch 5.1 – Physical Properties Physical Property – any characteristic that can be observed without changing the composition of the substance

1. Physical properties include characteristics gathered by the senses a) Examples: color, shape, smell, taste, texture

2. Characteristics obtained by measurements a) Examples: length, width, height, mass, volume, density, weight, temp.

3. State of Matter a) Examples: solid, liquid or gas dependant on temperature

4. Physical properties can be used to identify unknown substances a) Density – amount of mass in a given volume; [ = mass(g) / volume(cm3) ]

b) A golf ball would have a greater density than a table tennis ball

c) One could determine the composition of a piece of jewelry by comparing its density with the density of a known substance such as gold or silver

5. Some physical properties are size dependent a) Examples: length, width, height, volume, mass, weight 6. Some physical properties are size independent a) Examples: color, state, density

B. Physical Properties of Acids & Bases 1. Acids – have pH below 7 a) Properties include sharp smell and sour taste (**NEVER taste anything in a laboratory)

2. Bases – have pH above 7 a) Properties include slippery texture and bitter taste

3. Neutral – has pH of exactly 7 (not acidic or basic)

Ch 5.2 – Chemical Properties Chemical Property – characteristic of matter that allows it to change to something new; cannot be observed without changing the composition

1. Flammability – the ability to burn; how easily a substance will ignite and burn

2. Oxidation – reactivity with oxygen Some metals like silver and gold have lower reactivity levels which makes them good choices for jewelry

3. Toxicity – degree to which a substance can damage living tissue

a) Chlorine compounds change the chemical properties of pool water making it more acidic to eliminate algae, bacteria and insects

B. Chemical Properties of Acids & Bases 1. Acids – can react with (corrode) metals a) Tomato sauce is acidic enough to corrode aluminum foil

b) Acid rain (nitric acid) can damage plant and animal tissues

c) Sulfuric acid is useful in industry but can cause severe burns on human skin

2. Bases – used in cleaning products however if strong enough can also damage living tissue Ammonia can cause nosebleeds in some people

3. Salts – compounds made of metals and nonmetals when acids and bases react NaOH in drano; metallic base

Ch 5.3 – Physical & Chemical Changes Physical Change – any change in matter where the identity of the substance stays the same

1. Change in size or shape a) Ex: cutting watermelon into slices; changes size and shape but remains watermelon

2. Change of state a) Solid to liquid (ice melting) b) Liquid to solid (water freezing) c) Liquid to gas (water boiling) d) Gas to liquid (condensation)

B. Chemical Change – a change that occurs when a type of matter is changed into a different type with new characteristics

1. In a chemical change materials are formed that are different from the starting materials 2. A chemical change cannot easily if at all be reversed Example that can be reversed – oxidation of blood; breathe in oxygen release co2 Example that cannot be reversed – burning; baked cake turning back to raw ingredients

3. Examples include metal rusting, copper turning green (patina), wood paper or gas burning, food digesting, baking a cake, explosion of fireworks

4. Signs of chemical changes a) Release or absorption of energy in the form of light, heat or sound

b) Formation of a gas or solid (precipitate) not due to change of state

c) Change in color, smell or taste

C. Physical & Chemical Changes in Nature 1. Physical – weathering & erosion of rocks due to weather and animals

2. Chemical – weathering of rocks due to acid rain; color change of leaves in Fall