Chemistry Basics
What is the difference between Mass and Weight?
Mass is constant and weight depends on gravity
When I put an object on a scale to measure its mass, what unit should I set the scale to measure?
Grams
How many Significant Figures is in the number:
0.000 000 503 0
Four
0.000 000 503 0
Phase Changes are a subcategory of what type of change: Chemical or Physical?
Physical.
What is a hypothesis?
An educated guess that is Testable
Define Chemistry
Chemistry is the study of the composition of matter and the changes that matter undergoes
What units are used to measure volume according to the metric system?
Convert the following number into scientific notation:
0.000 000 503
5.03 x 10-7
Provide an example of a Phase Change.
Ice melting
The first step of the scientific process is making Observations. Provide an example of an observation that would be considered Qualitative.
Qualitative observations deal with the qualities of things (basically any observation that does not have a number). Ex: It had a golden color, it smelled like rotten eggs, etc
Provide an example of something that would be considered Matter.
Provide an example of something that would not be considered Matter.
Matter: anything that has mass and volume (ex: air, a desk, your body, etc)
Not Matter: anything that is considered just energy (ex: light, magnetic fields, etc)
When finding the density of an Aluminum object I do the following math calculation: 54grams/20mL = 2.7 ____. What unit should my final answer have?
Grams/mL or g/mL or g/cm3
When trying to calculate the density of a metallic object a student does the following calculation: 41.21 g/4.59mL = 8.978214 g/mL
Round the answer to the proper number of sig figs.
8.978214 g/mL --> 8.98 g/mL
Is the following equation an example of a Chemical, Physical, or Phase Change:
An iron bar being heated up:
Fe(s) --> Fe(s)
Physical only, composition stayed the same
When trying to measure the density of a solid aluminum object, 3 friends get the following results: 1.85, 1.86, and 1.88. Are their measurements accurate? Are they precise? The density of Al is 2.7g/mL
Precise but not accurate. Most likely their scales are not calibrated correctly or they read the device to measure volume incorrectly.
The Law of Conservation of Mass states that:
Matter cannot be created or destroyed in a chemical reaction. It is conserved (aka stays the same)
What is the density of water at standard temperature and pressure?
How does the above density compare to the density of salt water?
1g/1mL
Salt water is more dense (Salt Water > 1g/1mL)
Three students measure the masses of their bags of pennies using different scales around the room: 21.75 g, 280.112 g, and 10.15 g are their 3 measurements.
The total mass is 312.012 grams. Round this answer to the correct place value.
312.012 --> 312.01 grams
Is the following equation an example of a Chemical, Physical, or Phase Change:
N2 + 3 H2 --> 2 NH3
Why?
Chemical, the bonds were rearranged.
Explain the difference between a Scientific Law and a Scientific Theory.
Laws just give straight facts and typically involve mathematical equations; whereas, theories try to explain repeated observations/why something happens.
What is the difference between Pure and Applied Chemistry?
Pure = done for the sake of gaining knowledge
Applied = done to solve a problem
Many scientific units are based around water. What does 0 degrees Celsius and 100 degrees Celsius correspond to relative to water?
The melting and the boiling point of water at standard pressure.
To calculate the volume of their rectangular prism a student does the following calculation:
5.26cm x 19 cm x 3.0 cm = 299.82 cm3
Round the answer to the proper number of sig figs
299.82 cm3 --> 3.0 x 102 cm3
A student mixes two clear liquids. The resulting liquid changes black and begins to heat up. Is this a chemical, physical, or phase change? What evidence do you have?
Chemical because there was a color change and heat was released.
Identify the independent, dependent, and variables you would need to keep constant in the following experiment:
An experiment designed to see how the addition of different amounts of fertilizer affected the size of roots.
Independent: The amount of fertilizer you add
Dependent: how big the roots grow
Constants: amount of water, sunlight, heat, and the size of the pots the plants are in.