Unit 1: Density

Question 1

Mass

Answer 1

A measurement of how much “stuff” an object contains

Question 2

System

Answer 2

The part of the experiment or change we’re observing

Question 3

Surrounding

Answer 3

Everything around what you are observing

Question 4

Closed system

Answer 4

No particles can enter or leave the system

Question 5

Open system

Answer 5

Particles are free to enter or leave the system

Question 6

Law of conservation of mass

Answer 6

IN A CLOSED SYSTEM the mass before the change is the same as the mass after the change

Question 7

Physical change

Answer 7

A change that DOES NOT affect the identity or properties (intensive) or a substance

Question 8

Intensive properties

Answer 8

Properties that are useful to identify a substance

• Color
• Texture
• Reactivity
• Density

Question 9

Chemical change

Answer 9

A change that affects the structure and/or identity of a substance

Question 10

Volume in ml to cm cubed

Answer 10

1 to 1

Question 11

If mass is conserved

Answer 11

-# of particles should remain the same

Question 12

Significant figures

Answer 12

Use when: taking measurements or calculations

• Gives estimation of how confident we are in a measurement
• Before OR AFTER calculations

Question 13

Sig figs: before calculations

Answer 13

The last measured place has uncertainty
15.44 grams the last 4 has uncertainty
Confident to 4 sig figs: 3 certain about, 1 uncertain

Question 14

Sig fig: 160 m

Answer 14

• 2 sig figs
• The six is the last certain
• 0 is not significant

Question 15

sig fic 160.

Answer 15

• 3 sig figs
  All are significant
  Same as 160.0 (4 sig fig)
  Makes the 0 count

Question 16

0 rules

Answer 16

If last 0 is significant, add decimal point to the end

They count if:

• They re at the END of a number containing another decimal point
• They are between non zero numbers

Question 17

Sig fig 306 g does 0 count

Answer 17

Yes, in middle of non zero numbers

Question 18

Sig fig 0.012 do zeros count

Answer 18

No, they just hold place

Question 19

Sig fig 0.0830 m does the 0 count, how many sig figs

Answer 19

• 3 sig figs
• First two 0s at start, don’t count
• Last 0 does count

Question 20

Calculating with sig figs basic fule

Answer 20

You can NEVER be more confident in your answer than you are in your measurement

Question 21

Calculating with sig figs: addition and subtration

Answer 21

• Decimal place

- Round to the first uncertain place in your answer AFTER you add or subtract them together

Question 22

Calculating with sig figs: multiplication and division

Answer 22

• # of sig figs
• Figure out how many sig figs are in each component that is being multiplied or divided
• Take the least amount of sig figs and round the answer

Question 23

Independent variable

Answer 23

The variable that you choose values for, graphed to the x axis

Question 24

Dependent variable

Answer 24

The variable that changes based on your chosen changes, graphed on the y axis

Question 25

Measurment

Answer 25

Write all the values that you KNOW and guess once

Question 26

Density formula

Answer 26

Mass divided by volume

Question 27

Mass formula

Answer 27

Volume multiplied by density

Question 28

Volume formula

Answer 28

Mass divided by density

Question 29

Density

Answer 29

A ratio between mass and space(volume), a measure of of "crowded" particals are

Question 30

What two methods to find density

Answer 30

- Plot mass vs volume and find slope of best fit line ( density). If line doesn't go through (0,0) or if some points don't match up on the line, there was an error - Equation: (density equals mass divided by volume). Use when given a single data point

Question 31

Density is an intensive property which means

Answer 31

- It can be used to identify a substance - Different substances have different densities - If you have 2 substances with different densities you can conclude they are not the same

Question 32

Density: solids, liquids, gases

Answer 32

Solids typically have higher densities Liquids typically have middle densities Gasses typically have lowest densities

Question 33

Partical pictures: solids, liquids, gases

Answer 33

Solid: particals should be touching Liquid: particals should be close but not touching Gas: particals should be far apart

Question 34

Reacting means

Answer 34

Something has been added in | -Chemical change

Question 35

Closed system v open system particals

Answer 35

Closed: # of particals stays the same Open: # of particals changes

Question 36

Basic rules for partical pictures

Answer 36

Look at densities (solid, liquid, etc) Law of conservation of mass (in a closed system, because mass cannot be created or destroyed, number of particals stays the same bc the particals can't leave) Closed and open system

Question 37

Tearing a piece of paper in half 6 particals start Is this chem or physical change

Answer 37

Before: 6 particals touching in clump After: 6 particals in two clumps of 3 Physical change, intensive properties, does not change it it is still paper

Question 38

Boiling liquid in closed container 10 particals start Is this chem or physical change

Answer 38

Before: 10 particals liquid, particals close, not touching After: 10 particals, gas, particals far apart -Physical change-> number of particals, type of particals, does not change, just spread out

Question 39

Burning steell wool in open container (reacts with oxygen) 7particals start Is this chem or physical change

Answer 39

Before: all 7 particals touching After: 7 particals with 3, shaded, oxygen particals bc oxygen was added in Chemical: Reaction with different substances, steel to steel and oxygen, structure changed