Chapter 3: Matter & Energy DE CHEMISTRY: King William High School Chapter 3: Matter & Energy

1. Classification of Matter Pure substances (elements & compounds) have definite composition Mixture is two or more different substances physically combined Homogeneous mixtures – uniform throughout (solution) Heterogeneous mixtures – NOT uniform

2. States of Matter Solid – definite shape and volume Liquid – definite volume; NOT shape Gas – neither definite shape nor volume

Properties of Matter Physical properties – shape, color, MP, BP, FP Chemical properties – describe a substance changing into something new (metal rusting)

Physical change – changes in state (melting, freezing, etc.) Changes of Matter Physical change – changes in state (melting, freezing, etc.) Chemical change – changes into a new substance

4. Energy Kinetic v. potential Heat- energy associated with the motion of molecules Units (Joule and calorie) 1 cal = 4.184 J 1Cal = 1 kcal = 1000 cal Convert 6.2 x 102 J to cal and Cal.

5. Energy content for food Carbohydrate = 4kcal/g Fat = 9 kcal/g Protein = 4 kcal/g EX: You eat a meal that has 37 g of carbs, 19 g of fat and 23 g of protein. How many Calories did you intake?

6. Specific Heat Q = cmDT Table 3.11 on page 74 How much heat is released when 7 g of copper is cooled from 20oC to 10oC?

7. Changes in State Melting and freezing points Heat of fusion – energy needed to melt a substance Heat = mass x heat of fusion How much heat will be absorbed from 26.0 g of ice in a soft drink at 0oC if the heat of fusion = 334 J/g?

More… Heat of vaporization – energy required to turn a liquid to a gas at its BP Heat = mass x heat of vap.

Heating Curves Page 81

Cooling curves Opposite of heating curves

Combining energy calculations How much energy is needed to heat 100 g of diethyl ether from 5oC to its boiling point and boil it? The specific heat is 2.33 J/goC. The heat of vaporization is 357 J/g.