Introduction Chapter Quiz # 2 Study Guide

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INTRODUCTION CHAPTER QUIZ # 2 STUDY GUIDE

1)Know how to solve density problems. Be able to use your knowledge of density to predict how things will happen in the real world.

2)Atomic theory: Be able to calculate the correct numbers of subatomic particles in an atom from the periodic table of elements, be able to calculate mass, charge, and explain why atomic mass on the periodic table is a decimal and not a whole number.

3)Be able to tell the difference between elements, compounds, and mixtures.

4)Be able to explain how energy affects the atoms and molecules in a substance, and how the movement of the molecules brings about phase changes.

Density problems

1. What is the density of CO gas if 0.196 g occupies a volume of 100 ml?

D = M/V

M= 0.196g

V= 100mL 0.196g/100mL= 0.00196g/mL

2. A block of wood 3 cm on each side has a mass of 27 g. What is the density of the block? (Hint, don’t forget to find the volume of the wood.)

V= LxWxH 3cm x 3cm x 3cm= 27cm^3

M= 27g

V= 27 cm^3 27g/27cm^3= 1 g/cm^3

3. An irregularly shaped stone was lowered into a graduated cylinder holding a volume of water equal to 2 ml. The height of the water rose to 7 ml. If the mass of the stone was 25 g, what was its density?

V= 7mL – 2mL= 5mL

M= 25g

V= 5mL 25g/5mL= 5g/mL

4. A 10.0 cm3 sample of copper has a mass of 89.6 g. What is the density of copper?

M= 89.6g 89.6g/10.0 cm^3= 8.96 g/ cm3

V= 10.0 cm3

5. Silver has a density of 10.5 grams/cm3 and gold has a density of

19.3 g/cm3. Which would have the greater mass, 5cm3 of silver or 5cm3 of gold?

Gold has the greater mass. If they are the same size, the more dense material will have the greater mass.

6. If an object 1is more dense than object 2, which object would float on the other object?

More dense objects sink, therefore object 2 would float on object one.

7. Use your periodic table to answer fill out the chart, and answer the following questions:

8. When an atom has a charge, which particle changes number? _Electrons

9. If an atom has a 2+ charge, it means that it has 2 more ____Protons

than __Electrons .

10. Explain why atomic masses in the periodic table are not whole numbers.

The number of neutrons can vary for any element. That means that all elements have a variety of atomic masses. All of the various atomic masses for an element are averaged together to give us the atomic mass on the periodic table.

11. How can you tell the difference between an element and a compound? An element is made up of one single type of atom that can be found on the periodic table. A compound is made up of 2 or more elements chemically combined. An element would be: Iron, Sodium, Copper. Compounds are: Carbon Dioxide, water (H2O), Salt (sodium chloride)

12. How can you tell the difference between a substance and a mixture?

A substance is made from on element or one specific compound- in other words it is “pure”. A mixture is a combination of 2 or more substances that can be easily separated without a chemical reaction.

13. Describe how energy changes and the molecules react during a phase change.

As the energy in a substance increases, the molecules vibrate faster, bumping into each other harder, making more space between the molecules. When the space becomes large enough the particles can change places (liquid state), and when they get far enough apart they escape completely. (gas state) As it cools the particles get closer together and the process reverses.