Physical versus Chemical Properties Unit II - Part 1 The study of matter

Reviewing MATTER Matter: anything that has mass and takes up space Mass – the amount of matter in something Volume – the amount of space something occupies Which of the following is matter? A car? A box? You?

What is a property? Property: a characteristic of a substance that can be observed

Physical Property Physical property: a property that can be observed without changing the identity of the substance. Examples: luster malleability: the ability to be hammered into a thin sheet ductility: the ability to be stretched into a wire melting point boiling point density solubility specific heat

Special Physical Properties Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure water = 0oC Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure water = 100oC

Chemical Properties Chemical property: a property that can only be observed by changing the identity of the substance Examples: flammability ability to rust reactivity with vinegar

Density Density is the amount of mass per unit of volume. Density can be used to identify a substance. The density of water is 1.0g/mL

Density Formula Remember: When calculating density, your answer must have two units! Ex: g/ml or lbs/gallon

Density Calculations Calculations: D = m/V = g/mL = g/cm3 Ex: A cube has a mass of 2.8 g and occupies a volume of 3.67 ml. Would this object float or sink in water? Mass = 2.8 g Volume = 3.67 mL D = 2.8g/3.67 mL= 0.76 g/mL This object would float in water because its density is less than water (1.0 g/mL).

Density Practice What is the density of a block of marble that occupies 310 cm3 and has a mass of 853 g?

Density Practice A car engine has a mass of 450.0 kg. If the engine has a volume of 4.5 L, what is its density?

Density Practice Diamond has a density of 3.26 g/cm3. What is the mass of a diamond that has a volume of 0.35 cm3?

Density Practice What is the volume of a sample of liquid mercury that has a mass of 76.2 grams, given that the density of mercury is 13.60 g/mL?

More Density Calculations Ex: A liquid has a mass of 25.6 g and a volume of 31.6 mL. Use the table below to identify the substance. M=25.6 g V=31.6 mL D = 25.6 g/31.6 mL D= 0.81 g/mL The substance is ethanol.

Physical and Chemical Changes Unit II—Part 2

Concept of Change Change: the act of altering a substance

Physical Change Physical change: a change that occurs that does not change the identity of the substance Phase Changes Tearing paper Crushing Rocks

Chemical Changes Chemical change: a change that occurs causing the identity of the substance to change Burning Digesting food Reacting with other substances (give an example per reviewer) A chemical change is called a chemical reaction

Chemical Changes Cont’d Indicators of a chemical change: Evolution of light Evolution of heat (produced or absorbed) Evolution of a gas/change in odor Color change (careful here) Formation of a precipitate

Is it Physical or Chemical? Change Physical Chemical Melting cheese Burning wood Milk souring (Do all students relate to this?) Wadding up paper Bicycle rusting