Pure Substances
Mixtures
Density
Physical Properties and Changes
Chemical Changes
100
two kinds of pure substances
element and compound
100
two kinds of mixtures
homogeneous and heterogeneous
100
which is less dense - iron or feathers?
feathers
100
example of a physical property
color, size, shape, density, temperature, weight, mass, etc.
100
Name a clue that suggests that a chemical change/reaction has occurred.
(any one of the examples we gave)
200
example of a pure substance
(any element or compound)
200
example of a heterogeneous mixture
(any mixture in which you can see different ingredients)
200
what do you need to know to determine an object's density?
the mass (grams) and volume (cm cubed) of the object
200
how is a physical change different from a chemical change?
after a physical change, the substance is still the same substance - it is just hotter, colder, broken into smaller pieces, mixed with something else, etc. After a chemical change, a new substance has been formed.
200
How can you prove that a chemical change/reaction has taken place?
You must show that a new substance has been formed.
300
example of a compound
(any compound)
300
another name for a homogeneous mixture
solution
300
describe the particles in gold (density 19.3 g/cm cubed) as compared to the particles in aluminum (density 2.7 g/cm cubed)
gold particles are closer together (packed more tightly)
300
Which describes a physical property and why? 1. a cookie turns golden brown in the oven 2. cookie batter becomes solid in the oven 3. cookie batter melts when it is put in the oven
Cookie batter melts when it is put in the oven. Things normally melt when heated up and become solid when cooled down.
300
Is an activated glow stick undergoing a chemical change? Why do you think so?
Release of light energy is a clue that a chemical reaction is happening.
400
difference between an element and a compound
element has only one kind of atom; compound has more than one kind.
400
how could you separate a mixture of iron filings, sand, and pepper using physical properties?
iron filings - magnetic sand - sinks in water pepper - floats in water Must evaporate the water from the isolated sand and pepper.
400
will an object whose volume is 150 cm cubed and mass is 50 grams float?
yes
400
When a muffin gets bigger in the oven, is it a physical change or a chemical change?
Could be physical (size) or chemical (production of carbon dioxide from baking soda)
400
When iron gets rusty, for every 4 iron atom reactants, 6 oxygen atom reactants are needed. Describe the atoms in the product of the reaction (rust).
For every 4 irons, there are 6 oxygens.
500
how are pure substances different from mixtures?
all of the particles in a pure substance are the same; more than one kind of particle (ingredient) in a mixture
500
how is a mixture of hydrogen and oxygen different from a compound made of hydrogen and oxygen?
the hydrogen and oxygen are not attached to each other in the mixture and the ratio is not constant/fixed; the hydrogen and oxygen atoms are attached (bonded) to each other in the compound in a constant ratio (H2O, H2O2)
500
You have a block of pure aluminum (density = 2.7 g/cm cubed) which sinks in water. You also have a boat made of pure aluminum. Why doesn't your boat sink?
Although the boat has a lot of mass, the space inside causes the boat to take up a lot space, so its mass/volume is less than 1 g/cm cubed.
500
It is easy to pull the pepperoni out of the mixture known as a pepperoni pizza. Since it is not easy to pull the flour out of the mixture known as chocolate chip cookie dough, is the mixture the result of a physical change or a chemical change? Why or why not?
Physical change - no gas released, no unexpected change in termperature, no unexpected change in color - the flour was just mixed with the sugar, butter, and chips.
500
Describe a chemical reaction that we observed in class and tell how you know there was probably a chemical reaction.
(any of the reactions from the stations)
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