Name ____________________ CHEM 1004 Homework #2

Name ____________________
CHEM 1004
Homework #2
Spring 2011
This homework is due on Wednesday, January 19, at class time. The assignment will be
accepted up until the start of class on Thursday, January 20, with a 20% penalty. Assignments
turned in after class that day will receive no credit, though I will look through them if you want
me to.
1. (5 points) State whether each of the following properties is a physical or a chemical
a. chlorine gas is green
b. copper wire conducts electricity _______________________
c. aluminum does not rust _________________________
d. hydrogen reacts with oxygen _____________________________
e. table salt melts at 1474 °F ___________________________
2. (5 points) State whether each of the following undergoes a chemical change or a physical
a. water boiling away in a pot ____________________________
b. an egg being hard-boiled
c. a piece of iron rusts
d. dry ice turns into vapor at room temperature _____________________
e. a nail being bent in a vice ________________________________
3. (6 points) In the following description of zinc, indicate which of the properties indicated
are physical properties and which are chemical properties.
Zinc is a silver-gray-colored metal that melts at 420°C. When zinc granules are added to
dilute sulfuric acid, hydrogen is given off and the metal dissolves. Zinc has a hardness on
the Mohs scale of 2.5 and a density of 7.13 g/cm3 at 25 °C. It reacts slowly with oxygen
gas at high temperatures to form the compound zinc oxide.
4. (10 points) For each of the following, indicate whether it is a pure substance or a mixture.
For pure substances, further indicate whether the substance is an element or a compound.
For mixtures, further indicate whether the mixture is homogeneous or heterogeneous.
a pinch of sugar dissolved in water
the contents of a balloon filled with
hydrogen and oxygen gas
water formed when hydrogen gas is
burned in the presence of oxygen
a sample of Gulf of Mexico water from
an area contaminated by the BP oil
Pure Substance or Mixture?
If pure substance – element or compound?
If mixture – homogeneous or heterogeneous?