What are Hypotheses, Laws, Theories, Mixtures, Compounds, Elements, and Physical/Chemical Changes in Chemistry?
Identify each of the following statements as being most similar to a hypothesis, a law, or a theory. Explain your reasoning.
(a) Falling barometric pressure precedes the onset of bad weather.
(b) All life on earth has evolved from a common, primitive organism through the process of natural selection.
(c) My truck’s gas mileage has dropped significantly, probably because it’s due for a tune-up.
How does a heterogeneous mixture differ from a homogeneous mixture? How are they similar?
How does an element differ from a compound? How are they similar?
Classify each of the following as an element, a compound, or a mixture:
(a) copper
(b) water
(c) nitrogen
(d) sulfur
(e) air
(f) sucrose
(g) a substance composed of molecules each of which contains two iodine atoms
(h) gasoline
Classify each of the following changes as physical or chemical:
(a) coal burning
(b) ice melting
(c) mixing chocolate syrup with milk
(d) explosion of a firecracker
(e) magnetizing of a screwdriver
Identify the following properties as either extensive or intensive:
(a) volume
(b) temperature
(c) humidity
(d) heat
(e) boiling point
A large piece of jewelry has a mass of 132.6 g. A graduated cylinder initially contains 48.6 mL water. When the jewelry is submerged in the graduated cylinder, the total volume increases to 61.2 mL.
(a) Determine the density of this piece of jewelry.
(b) Assuming that the jewelry is made from only one substance, what substance is it likely to be? Explain.
2. Which one is a law? Let us consider the statements individually; 2) Falling barometric pressure precedes the onset of bad weather - This is a law because it has been proven experimentally. All life on earth has evolved from a common, primitive organism through the process of natural selection - This is a theory because it is just an explanation of an observation without empirical proof. My truck’s gas mileage has dropped significantly, probably because it’s due for a tune-up - This is a hypothesis because it is a mere guess.