Density, and Percent Error Practice

Show all work (formula, substitutions, and answer with units). Error! Objects cannot be created from editing field codes.

1. What is the density of a piece of cement that has a mass of 8.96 g and a volume of 3.07 cm3?

2. Limestone has a density of 2.72 g/ml. What is the mass of 99.70 cm3?

3. Calcium chloride has a density of 2.5 g/cm3. What is the volume of 7.48 g?

4. What is the density of Hg if 164.56 g occupy a volume of 12.1 cm3?

5. What is the mass of 2.15 cm3 of Hg?

6. What is the volume of 94.2 g of Hg?

7. An irregular piece of aluminum with a mass of 9.867 g is dropped into 15.00 ml of water. The volume of water increases to 18.70 ml. What is the density of the aluminum?

8. If the actual density of aluminum is 2.70 g/ml, what is the percent error for problem #4?

Accuracy and Precision

Unknown substance was sucrose; density = 1.59 g/cm3

Student A Student B Student CDensity(g/cm3)

Error (g/cm3)

Density(g/cm3)

Error (g/cm3)

Density(g/cm3)

Error (g/cm3)

Trial 1 1.54 -0.05 1.40 -0.19 1.70 +0.11Trial 2 1.60 0.01 1.68 +0.09 1.69 +0.10Trial 3 1.57 -0.02 1.45 -0.14 1.71 +0.12Average 1.57 1.51 1.70Using the data table provided please answer the following questions:

1. Using their averages determine the percent error for each student.a.

b.

c.

2. Which student was the most accurate with his/her data and why?

3. Which student was the most precise with his/her data and why?

Match the correct vocabulary word with the definition.

a. constant c. independent variable e. control group g. hypothesis b. data d. experimental group f. experiment h. dependent variable

1._____a testable explanation of a situation2._____a procedure that tests a hypothesis by collecting information under controlled conditions

3._____in an experiment, the group that is the standard against which results are compared4._____in an experiment, the group that is exposed to the factor being tested5._____the factor that remains fixed in an experiment6._____the condition being changed7._____the factor that results from or depends on the changed variable8._____information gained from observation

Experimental Methods Practice:

In the scenarios below (1 -3), identify the following components of an experiment.

1. Independent variable 2. Dependent variable 3. Control4. Repeated trials 5. ConstantsUse the scenarios below (1-3) to write a title and a hypothesis using the following formats: 6. Title: The Effect of the (changes in the independent variable) on the (dependent variable)7. Hypothesis: If the (independent variable – describe how it will be changed), then the(dependent variable – describe the effect).

Scenario 1 Floor Wax

A shopping mall wanted to determine whether the more expensive “Tough Stuff” floor wax was better then the cheaper “Steel Seal” floor wax at protecting its floor tiles against scratches. One liter of each brand of floor wax was applied to each of 5 test sections of the main hall of the mall. The test sections were all the same size and were covered with the same kind of tiles. Five (5) other test sections received no wax. After 3 weeks, the number of scratches in each of the test sections was counted.

Scenario 2 Brands of Car Wax

Jack wanted to test which brand of car wax was most effective. He tested four brands of wax. He cleaned the hood of his car and removed the old wax. He measured four equal sections on the hood of the car. Each of the waxes was used to cover a section. An equal amount of wax, the same type of rag, and equal buffing were used. Five drops of water were placed on each square, and the diameter of each drop was measured (cm) (quantitative). Jack could have used a qualitative dependent variable by developing a rating scale for amount of shine, from dull to very shiny.

Scenario 3 Compost and Bean Plants

After learning about recycling, members of John’s biology class investigated the effect of various recycled products on plant growth. John’s lab group compared the effect of different-aged grass compost on bean plants. Because composition is necessary for release of nutrients, the group hypothesized that older grass compost would produce taller bean plants. Three flats of bean plants (25 plants/flat) were grown for 5 days. The plants were then fertilized as follows: (a) Flat A: 450 g of 3-month-old compost, (b) Flat B: 450 g of 6 month-old compost, and (c) Flat C: 0 g compost. The plants received the same amount of sunlight and water each day. At the end of 30 days the group recorded the height of the plants (cm).

Can you find what is wrong with these Scientific Method Experiments?

Scenario 4 Metals and Rusting Iron

In chemistry class, Allen determined the effectiveness of various metals in releasing hydrogen gas from hydrochloric acid. Several weeks later, Allen read that a utilities company was burying lead next to iron pipes to prevent rusting. Allen hypothesized that less rusting would occur with the more active metals. He placed the following into 4 separate beakers of water: (a) 1 iron nail, (b) 1 iron nail wrapped with an aluminum strip, (c) 1 iron nail wrapped with a magnesium strip, and (d) 1 iron nail wrapped with a lead strip. He used the same amount of water, equal amounts (mass) of the metals, and the same type of iron nails. At the end of 5 days, he rated the amount of rusting as small, moderate, or large. He also recorded the color of the water.

Unit 3 Matter & Energy

Chemistry—definition

Chemistry deals with the properties and reactions of substances.

2. Matter is anything that has ___________and occupies ________________.

It exists in three phases: _____________, ____________and ____________.

Fill in the table below about these three phases:

Phase How would you describe shape?

How would you describe volume?

3. Matter can be classified into ________categories—

____________________________, each of which has a __________

composition and a ______________set of properties.

____________________, composed of __________or more substances.

4. Pure substances are either _____________or _______________, whereas mixtures

can be either ___________________or _______________________.

Mixtures

1. Mixtures—definition:

2. There are two types of mixtures:

a. Homogeneous—definition:

Another name for a homogeneous mixture is a __________________.

b. Heterogeneous—definition:

. Chemical property:

o Example of a chemical property:

4. Physical property:

o Example of a physical property:

5. Physical vs. chemical change:

Classify the following as either physical (P) or chemical (C) changes:

a. ice melting

b. gasoline burning

c. food spoiling

d. log of wood sawed in half

Classify the following as pure substances or mixtures. Briefly support your decision.

A) mercury B) gold C) salt water D) sugarE) river water F) methanol G) gasoline H) cake mix

Classify the following as heterogeneous or homogeneous. Briefly support your decision.

A) Distilled water –B) oak lumber –C) iron bar – D) a pear –E) a Caesar salad -F) air – G) helium –H) salt water –I) sugar and sand -J) granite -

Classify the following as an element, a compound, a solution, or a heterogeneous mixture. Briefly support your decision.

A) Mercury B) filtered air C) a tangerine D) aluminumE) a pencil F) gasoline G) sulfuric acid H) sulfurI) oat bread J) coffee (in the mug) K) a pen L) potassiumM) chocolate chip cookie N) glass O) carbon dioxide P) a tacoQ) kool aid R) muddy water S) brass T) goldU) graphite V) oxygen gas W) ethylene glycol X) soilY) baking soda (NaHCO3) Z) ocean water AA) orange juice w/pulp BB) benzeneCC) iron filings DD) limestone EE) chromium FF) steel

Provide complete, detailed, yet concise responses to each of the following questions.

1) What makes a substance ‘pure’?

2) Is it practical to have a substance that is 100% pure? Why or why not?

3) Mixtures can be broken down into what two types of classification?

4) What is the difference between the two?

5) A homogeneous mixture can be broken down into what classifications?

6) How are elements defined? Elements are homogeneous, pure substances composed of one type of atom and resist chemical simplification.

7) How do solutions differ from compounds?

1)What is a physical property?

2) What are some examples of physical properties?

3) What is it called when an object goes through physical change from a solid to a liquid or a liquid to a gas?

4) What doesn’t change during a physical change?

5) Why can it be difficult at times to distinguish between chemical and physical changes?

6) What is a chemical property?

7) What are some examples of chemical properties?

8) When there is a chemical change, what are the materials said to be going through?

Identify each of the following as an example of a physical property or a chemical property.

1. Silver tarnishes when it comes in contact with hydrogen sulfide in the air.

2. A banana is yellow.

3. A sheet of copper can be pounded into a bowl.

4. Barium melts at 725 C.

5. Gasoline is flammable

6. A diamond is the hardest natural substance.

7. Helium does not react with any other element.

8. A bar of lead is more easily bent than is a bar of aluminum of the same size.

9. Potassium metal is kept submerged in oil to prevent contact with oxygen or water.

10. An apple will turn brown is left in oxygen.

11. Diamond dust can be used to cut or grind most other materials.

12. Acid in tomato sauce can corrode aluminum foil.

13. Rocks containing carbonates can be identified because they fizz when hydrochloric acid is applied.

14. A piece of charcoal, which is mostly the substance carbon, glows red, gives off heat, and becomes a gray ash.

15. What is potential energy and kinetic energy?

16. Define the law of conservation of mass

Unit 3 Atomic Structure:

1. Differentiate among the electron, proton, and neutron, and indicate the electrical charge and relative mass associated with each particle.

2. Define atomic number and mass number and their relationship to isotopes.

3. Define isotope, nucleon, and nuclide.

4. Given the atomic number and mass number, list the number of protons, neutrons, and electrons in an atom, or given the number of particles, determine the atomic number and mass number

Sub-atomic particles: Protons, Neutrons and electrons

Type symbol charge mass (in a.m.u.’s) Location

Proton P positive 1 nucleus

Neutron N neutral 1 nucleus

Electron e- negative 0 shells/orbits

Atoms (or elements) are neutral combinations of protons, neutrons and electrons

Ions are atoms (or groups of atoms) that have gained or lost electrons to obtain a net charge.

Cations are positively charged ions (they have lost electrons)

Anions are negatively charged ions (that have gained one or more electron)

Isotopes are varieties of the same element that have different masses due to more or less neutrons in

the nucleus. Isotopes of the same element react the same. (heavy water is just like water only more

dense).

Element Symbol Mass # of protons # of neutrons # of electrons

Carbon C 12 6 6 6

Helium He 4 2 2

N 7

28 13

S 18

79 79

24 12

Sn 69

Hydrogen

(tritium)

1 2

Uranium 235

47

Ir 77

240 94

125 84

Element/

ION

Symbol Mass # of protons # of neutrons # of electrons

Carbon

cationC+4 12 6 6 2

H+1 1 0 0

Nitrogen

anionN-3 7

33 36

S-2

35 45 36

Mg+2 24 12

Sn+2 69

9 10

U+1 235

47 46

Ir-2

20 18

Cesium 54

1. Calculating Average Atomic Mass for Argon (round all answers to 2 decimal places):

Argon has 3 naturally occurring isotopes:

0.337% abundance of Ar-36

0.063% abundance of Ar-38

99.63% abundance of Ar-40

Calculated Average Atomic Mass of Argon:

2. Determine the Average Atomic Mass of Sulfur:

Sulfur has 4 naturally occurring isotopes:

95.00 % abundance of S-32

0.76 % abundance of S-33

4.22 % abundance of S-34

0.014 % abundance of S-36

Calculated Average Atomic Mass

3. Determine the Average Atomic Mass of Zinc:

Zinc has 5 naturally occurring isotopes:

48.84 % abundance of Zn-64

27.62 % abundance of Zn-66

4.12 % abundance of Zn-67

18.71 % abundance of Zn-68

0.69 % abundance of Zn-70

Calculated Average Atomic Mass

1. Determine the % Abundance of the two isotopes of Copper (Cu-63 and Cu-65)Based on the average atomic mass of Copper, which isotope should have the higher percentage?

Circle: Cu-63 and Cu-65

_______________________ % abundance of Cu-63 _______________________ % abundance of Cu-65

2. Determine the % Abundance of the two isotopes of Boron (B-10 and B-11)

_______________________ % abundance of B-10 _______________________ % abundance of B-11

3. Determine the % Abundance of the two isotopes of Chlorine (Cl-35 and Cl-37):

_______________________ % abundance of Cl-35 _______________________ % abundance of Cl-37

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