Chemistry 0-5- Chemistry Math Practice

Chemistry Math Practice

Multiple Choice

This word means a substance that has a definite known composition

• Chemical

• Sucrose

• Organic

• Candela

Multiple Choice

What is the term for a substance that can be broken down into two or more elements

• Atom

• Mole

• Ampere

• Compound

Multiple Choice

Is a 197-lb weight lifter light enough to compete in a class limited to those weighing 90 kg or less?

• Yes

• No

Lesson Objectives

• Review Different Calculations and Analytical Techniques used frequently in chemistry

  • Scientific Notation

  • Density

  • Percent Error

​Scientific Notation

• In science, we have instances where we work with very large or very small numbers.

• In order to make them easier to read, we often write them in a form called Scientific Notation

  • When Handwritten: M×10ⁿ

    • M= any number ≥1 and less than 10

    • n= any whole number

  • When Typed: MEn

    • Note: The E must be capitalized!!!

​Converting to and from Scientific Notation

• Converting in and out of Scientific Notation is a matter of moving the decimal place the same number of spaces as the n

  • When you are moving the decimal to the left, n is positive​

  • When you are moving the decimal to the right, n is negative

​Scientific Notation Sample Problem 1

• Write 76300 in scientific notation

  • Step 1: Find M: Make our coefficient a number between 1 and 10

    • M= 7.6300

  • Step 2: Find n: Count how many decimal places you had to move to get to that number

    • We moved our decimal place to the left, so we know we will have a positive n Value

  • Step 3: Plug your M and n values into the scientific notation format

    • 7.63 × 10⁴

    • If you were to type this in a computer program, you would type 7.63E4 WITH NO SPACES

​Using Scientific Notation on your Calculator

• Step 1: Enter your M value

• Step 2: Hit your 2nd key

  • The top left corner is a different color

• Step 3: Hit your Scientific notation key​

  • Usually, the X^-1 button above the number 7​

• Step 4: Type the n value

• When doing calculations involving scientific notation, use parentheses!!

Multiple Choice

What is the study of the composition, structure, and properties of matter, the processes that matter undergoes, and the energy changes that accompany these processes called

• Physics

• Chemistry

• Science

• Math

Multiple Choice

Which of the following numbers are in proper Scientific Notation?

• 0.95 × 10⁶

• 9.5 × 10⁶

• 95.6 × 10⁶

​Accuracy and Precision

• In science, Accuracy and Precision mean different things

  • Accuracy:​ the closeness of a measurement to a correct or accepted measurement

    • Were you in the ballpark of what you should have gotten?

  • Precision: The closeness of a set of measurements of the same thing measured the same way

    • Did you get the same result every time you did it?

​Percent Error

• Percent Error: A measure of how inaccurate a measurement is, standardized to how large the measurement is

  • How far off were you?

  • P_E: The Number you actually got in your experiment/the number you predicted

  • P_T: The "True" Value

• A negative Percent error means you were lower than you should have been, a positive percent error means you were higher

​Percent Error Sample Problem 1

• A student estimated the mass of a block to be 240 grams. When the block was put on a scale, the mass was 265 grams. What was the student's Percent Error?

  • Step 1: Identify your variables

    • P_E: 240

    • P_T: 265

  • Step 2: Plug your values into the equation and Solve

​Percent Error Sample Problem 2

• Joshua uses his thermometer and finds the boiling point of ethyl alcohol to be 75.0°C. He looks in a reference book and finds that the actual boiling point of ethyl alcohol is 80.0°C. What is his percent error?

  • Step 1: Identify your variables

    • P_E=75

    • P_T= 80

  • Plug your values into the equation

​Density

• Density: measures the ratio of mass to volume

  • How much stuff is in a given Space

    • Can affect the properties of a substance, like whether or not it floats

  • D=m/v

    • The unit is described as a mass unit/volume unit

      • g/l

      • kg/cm³

​Density Sample Problem 1:

• You have a rock with a volume of 15cm³ and a mass of 45 g. What is its density?

  • Step 1: Identify what you know

    • mass=45 g

    • volume= 15 cm³

    • density=?​

​Density Sample Problem 1:

• You have a rock with a volume of 15cm³ and a mass of 45 g. What is its density?

  • Step 1: Identify what you know

    • mass=45 g

    • volume= 15 cm³

  • Step 2: Check if you need to convert anything

    • Nope!

  • Step 3: Plug into your equation and solve​

​Density Sample Problem 2:

• You decide you want to carry a boulder home from the beach. It has a volume of 27,000 cm³ and is made of granite, which has a density of 2.8 g/cm³. How much will this boulder weigh?​

  • Step 1: Identity​ what you know

    • mass=?

    • Volume= 27,000 cm³

    • Density= 2.8

​Density Sample Problem 2:

• You decide you want to carry a boulder home from the beach. It has a volume of 27,000 cm³ and is made of granite, which has a density of 2.8 g/cm³. How much will this boulder weigh?​

  • Step 1: Identify​ what you know

    • mass=?

    • Volume= 27,000 cm³

    • Density= 2.8

  • Step 2: Check to see if you need to convert anything

    • Nope

  • Step 3: Plug your values into your equation