Sig Figs and Matter/Energy

Question 1

What is the rule when multiplying and dividing two numbers in chemsitry?

Answer 1

You write your final answer in the least number of SF when x and dividing

Question 2

PRACTICE:

1.271 x 1.6 = _______

Answer 2

1.271 has 4 SF, while 1.6 has 2 SF. Because we are multiplying, we write out final answer in the least number of SF based on the original values. 2 SF is the least number of SF, so the final answer will be written in 2SF

1.271 x 1.6 = 2.0336 = 2.0

Question 3

T/F: This number has 4 sig figs - 1988

Answer 3

True

Question 4

How many SF are in the number: 911?

Answer 4

3 SF

Question 5

What is the rule when adding and subtracting numbers in chemistry?

Answer 5

The final answer is the least number of decimal places for + and -

Question 6

Practice:

1.276 + 1.1001 = ______

Answer 6

1.276 has three deecimals places, while 1.1001 has 4 decimal places. The final answer is always written based on the least number of decimal places when + and -, so we must write out final answer with three decimal places.

1.276 + 1.1001 = 2.3761 = 2.376

Question 7

Practice:

7.812 - 1.6 x 8.13 / 2.765

Answer 7

-2. OR -2

1 SF; for explanation look at notes

Question 8

How many SF in: 540.

Answer 8

3SF

Question 9

How many SF in: 540

Answer 9

2 SF

Question 10

How many SF in: 18000 pens

Answer 10

5 SF

we count all the numbers if something designates a number

Question 11

How many SF in: 2.9 x 10⁸

Answer 11

2 SF

dont count the 10⁸

Question 12

What are the 2 big problems in the world currently?

Answer 12

• plastics
• chemicals in ozone layer

Question 13

Define: Energy

Answer 13

ability to do work

Question 14

What are the 4 types of energy. Know the definition of each

Answer 14

Thermal energy: is heat - will mainly focus on this in chem
Potential enerty: is stored energy
Kinetic energy: is E of motion
Radiant energy: is solar E from the sun

Question 15

The energy given off is usually in the form of ________ energy

Answer 15

thermal (heat)

Question 16

What are the 2 types of thermal (heat) energy in a chemical reaction?

Answer 16

Exothermic RXN
Endothermic RXN

Question 17

What is the difference between an exothermic and endothermic RXN?

Answer 17

Types of Thermal (heat) Energy:

• Exothermic: (heat) E flows OUT the system
• Endothermic: (heat) E flow INTO the system

Question 18

What ate the two units of heat energy? Which one is the SI unit for energy?

Answer 18

Untis of Heat Energy:

• Joule (J) - is the SI unit for heat E
• Calorie

Question 19

Know how many Calories (C) are in a kcal that are in a calories (cal)

Answer 19

1C = 1kcal = 1000 calories

Question 20

How many Joules (J) are in 1kJ?

Answer 20

1 kJ = 1000 J

Question 21

How many Joules (J) are in 1 cal?

Answer 21

1 cal = 4.184 J

Question 22

Convert 4.5 kJ to cal

Write the answer concerning the SF rules

Answer 22

= 1076 cal

= 1100 cal (2SF)

Question 23

What is the difference between temperature and heat?

Answer 23

Temperature: a measure of how hot/cold a substance is COMPARED to another substance

Heat: is thermal energy that flows from a substance of a high temperature to low temperature

Question 24

Heat moves from a substance of _____ temperature to _______ temperature

Answer 24

high
low

Question 25

What is the formula for converting Celcius to Farenheight

Answer 25

F° = 1.8 (C°) + 32°

Question 26

What is the formula for converting Farenheight to Celcius

Answer 26

C° = F° - 32 / 1.8

Question 27

What is the formula for converting Celcius to Kelvin

Answer 27

K = C° + 273°

Question 28

Practice: Liquid nitrogen is often used as a coolant for low-temperature experiment has boiling point of 77K. What is the temperature on the farenheight scale?

Answer 28

-321 F°