Chapter 2 & 3 Flashcards
Energy
the ability to do work
Potential energy
energy stored for later use
kinetic energy
the energy of motion
what is heat
kinetic energy because it is associated with motion of particles
Temperature
a measure of how hot or cold a substance is compared to another substance
How does heat flow?
from a substance a higher temperature to a substance at lower temperature until the temperatures are the same
3 types of thermometer scales
- Fahrenheit
- Celsius
- Kelvin
Fahrenheit •formula •how many units is it based on •freezing point •boiling point
- (1.8 x C) + 32
- based on 180 units
- 32 F
- 212 F
Celsius •formula •how many units is it based on •freezing point •boiling point
- (F-32) / 1.8
- based on 100 units
- 0 C
- 100 C
Kelvin •formula •how many units is it based on •freezing point •boiling point
- C + 273.15
- based on 100 units
- 273 K
- 373 K
hypothermia
•F
•C
- less than 96.8 F
* less than 36 C
“Normal”
•F
•C
- 98.6 F
* 37 C
Normal Range
•F
•C
- 96.8 - 100.4 F
* 36 - 38 C
Hyperthermia
•F
•C
- greater than 100.4 F
* greater than 38 C
Death
•F
•C
- greater than 105.8 F
* greater than 41 C
How is heat measured?
in Joules or calories
Calories
defined amount of energy
Conversions of joules, calories, and kilocalories •1 calorie (cal) = \_\_ joules •1 kJ = \_\_ joules •1 kJ = \_\_ calories (cal) •1 kJ = \_\_ Calories (Cal)
- 4,184 J
- 1,000 J
- 1,000 J
- 1,000 cal
- 1 Calorie
1 calorie is the energy required to…
raise the temp of one gram of water by 1 C
Specific heat •definition •allows comparison... •example: Earth's moon (High 107 C, low -1576 C) Mars (High 20 C, low -60 C) Which one has a larger specific heat?
- the amount of heat that raises the temperature of 1g of a substance by 1 C
- of heat transfer between substances
- mars rock
For the same amount of heat added, a substance with a large specific heat
•has a smaller increase in temperature
•has a greater increase in temperature
•has a smaller increase in temperature
When water cools, the surrounding air
•cools
•warms
warms
Sand in the desert is hot in the day and cool at night. Sand must have a
•high or low specific heat
low specific heat
calorimeter
•what is it used for
•what does it contain
•what 2 things does it indicate
- used to measure heat transfer
- contains a reaction chamber and thermometer
- indicates heat lost by a sample
- indicates the heat gained by water
Typical Energy (caloric) values for 3 food types
- Carbohydrate (kJ/g ; kcal/g)
- Fat (kJ/g ; kcal/g)
- Protein (kJ/g ; kcal/g)
- 17 kJ/g ; 4 kcal/g
- 38 kJ/g ; 9 kcal/g
- 17 kJ/g ; 4 kcal/g
Matter
•definition
•how many physical states exist
- the material that makes up a substance
* 3
Pure substance
•definition
•what is it when it is composed of one type of
•what is it when composed of 2 or more elements combined in a definite ratio
- matter with a specific composition
- element
- compound
2 types of pure substances
- elements (copper)
2. compounds (water)
2 types of mixtures
- Homogeneous (Brass - copper and zinc)
2. Heterogeneous (water and copper)
elements
pure substances that contain atoms of only one type
compounds
contain 2 or more elements in a definite ratio
Mixture is matter that consists of
•4 things
- 2 or more substances that are physically mixed, not chemically combined
- substances that can be separated by physical methods
- heterogeneous composition
- homogeneous composition
Heterogeneous compostion
- is uniform throughout
* can see separate parts (may be opaque)
Homogeneous liquid
- composition is not uniform throughout
- can’t see separate parts, if liquid-will be clear
- air
Physical properties
•what is it used for
•how are they observed
•change?
- used to describe a substance
- observed or measured without changing the identity of a substance
- do not change the amount of substance
Physical change
- the identity and composition of the substance do not change
- that state can change or the material can be torn into smaller pieces
Sublimation •definition •example •where does it take place •what is it used for
- occurs when a solid changes directly to a gas
- dry ice (sublimes at -78 C)
- in a frost-free refrigerator
- used to prepare freeze-dried foods for long term storage
Evaporation
occurs when molecules on the surface gain sufficient energy to form a gas
Condensation
Occurs when gas molecules lose energy and form a liquid
Boiling
Occurs when molecules within the substance gain sufficient energy to become a gas, as indicated by formation of vapor bubbles
Heating curve
•5 steps
- Heating ice from -15 C to 0 C
- Melt ice at 0 C
- Heating water from 0 C to 100 C
- Boiling water at 100 C
- Heating steam from 100 C to 200 C
Chemical properties
describe the ability of a substance to change into a new substance
During a chemical change…
reacting substances form new substances with different compositions and properties
Intermolecular forces
•definition
•what does it determine
•3 main forces (called Van Der Waals forces)
•attractive forces that act between different molecules
•determines physical properties of molecular compounds, liquid or solid or gas at a given temp
1. Dipole
2. London dispersion force
3. Hydrogen bonding
