8th grade Properties, Changes, & States Test
A sample of ammonium nitrate is decomposed into nitrogen gas, oxygen, and water. If 40 g of ammonium explodes and 14 g of nitrogen and 8 g of oxygen are formed, how many grams of water are formed? How do you know?
18 grams of water are formed, explained by the Law of Conservation of Mass.
Which ones of the following can be considered a chemical change? a) rusting metal chair b) break down H2O2 into water and oxygen c) condensation of water on the side of a cold beverage d) forming a sedimentary rock from pressure
A & B are chemical changes
Which ones of the following can be considered a physical change? a) dissolving salt in water b) Burning a marshmallow over a fire c) Souring of milk d) Evaporation of water e) Grinding a crystal into a fine powder
A, D, E are all physical changes
What is a physical change?
Any change to the physical properties of the substance: shredding, chopping, painting, dissolving, mixing.
Explain why the evaporation of water is a physical change and not chemical.
Both water in the liquid and gaseous state have the formula H2O. No change in the chemical composition has occurred.
What characteristics define a solid?
Definite shape, definite volume
A sample of copper has a mass of 76.5 g and a volume of 8.5 cm3. What is the density?
Density = 76.5/8.5 = 8.89 g/cm3
Formula for Density
Density = mass/volume
True or False? When a substance changes from one state to another, there is a change in the composition of the substance.
False
The density of silver is 10.5 g/cm3. What is the mass of a piece of silver with a volume of 24 cm3?
Mass = 10.5 x 24 = 252 grams
What is mass?
Mass is the amount of matter in an object.
State the Law of Conservation of Mass
Matter cannot be created or destroyed in ordinary chemical and physical changes.
Define matter.
Matter is anything that has mass and occupies space.
What is a chemical change?
Results in the production of a new substance (atoms are rearranged to make something new).
Give an example of a chemical change.
Rusting, Burning, Corrosion, Rotting
Describe the speed or movement of the particles in a solid, liquid or gas.
Solid = vibrate in place Liquid = flow and slide Gas = move independently & far apart
What is volume?
The amount of space an object takes up
Define density.
The measure of how much mass is in a certain volume.
The density of uranium is 18.9 g/cm3. What is the volume of a sample of uranium with a mass of 58 grams?
Volume = 58/18.9 = 3.07 g/cm3
List 3 indicators a chemical change is occurring.
change in color, gas (bubbles or fizz), precipitate is formed, odor, energy is absorbed or released
What characteristics define a liquid?
definite volume, no definite shape
Give an example of a physical change.
melting, boiling, dissolving, ripping
What characteristics define a gas?
no definite shape or volume
How would you classify the color and smell of a flower?
physical property
Is density a physical or chemical property?
physical property
List 3 physical properties of gold
shiny luster, solid at room temp, malleable
What are the 4 states of matter?
solid, liquid, gas, plasma
Show the difference in the particle arrangement in a solid, liquid or gas.
solid, tightly packed liquid, more space & moves more freely gas, very spread out
