2. Classify the following as being a physical (P) or chemical (C) change. A. Sodium hydroxide dissolves in water.
B. Hydrochloric acid reacts with potassium hydroxide to produce a salt, water, and heat.
C. A pellet of sodium is sliced in two.
D. Water is heated and changed to steam.
E. Potassium chlorate decomposes to potassium chloride and oxygen gas.
F. Iron rusts.
G. When place in water, a sodium pellet catches on fire as hydrogen gas is liberated.
H. Evaporation of alcohol.
I. Ice melting.
J. Milk sours.
K. Sugar dissolves in water.
L. Wood rots.
M. Pancakes cooking on a griddle.
N. Grass growing in a lawn.
O. A tire is inflated with air.
P. Food is digested in the stomach.
Q. Water is absorbed by a paper towel.
R. Grinding coffee beans
S. Shredding up your homework (please DO NOT do this)
T. Baking chocolate chip cookies

The frequency of vibrations of a vibrating violin string is given by f = 1 2l t ρ where l is the length of the string, t is its tension, and ρ is its linear density.† (a) find the rate of change of the frequency with respect to the following. (i) the length (when t and ρ are constant) (ii) the tension (when l and ρ are constant) (iii) the linear density (when l and t are constant) (b) the pitch of a note (how high or low the note sounds) is determined by the frequency f. (the higher the frequency, the higher the pitch.) use the signs of the derivatives in part (a) to determine what happens to the pitch of a note for the following. (i) when the effective length of a string is decreased by placing a finger on the string so a shorter portion of the string vibrates df dl 0 and l is ⇒ f is ⇒ (ii) when the tension is increased by turning a tuning peg df dt 0 and t is ⇒ f is ⇒ (iii) when the linear density is increased by switching to another string df dρ 0 and ρ is ⇒ f is ⇒