Classification of Matter
What is an example of an element?
Carbon (C)
Oxygen (O)
Hydrogen (H)
Sodium (Na)
What is cohesion?
when water is attracted to water
In a chemical reaction, atoms are ______. The _____ is the same on the reactants and products side.
rearranged; mass
Will you ace this first unit test?
Yes!
DUH!
100%
Absolutely.
What makes something a compound? Give an example.
Compounds are two or more elements chemically bonded together.
H2O
CO2
NaOH
If a substance has a pH of 4, what is it?
acid
Calculate the number of atoms in the reactants and products in this chemical reaction:
C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy
Is the number of atoms the same, less, or more in the products vs. reactants?
C - 6
H - 12
O - 18
Number of atoms is the same in the reactants and products
When soap drops are added to water, a floating needle sinks. Why?
A. The soap increased the weight of the needle.
B. The soap reduced the surface tension of the water.
C. The soap molecules repelled the needle molecules.
D. The soap increased forces between water molecules.
B. The soap reduced the surface tension of the water.
What is a homogenous mixture?
a mixture of two or more substances that have the same uniform composition and appearance throughout
How does cohesion show up?
When water clings to other water molecules like magnets
or When water keeps its shape as a water droplet
If a substance has a pH of 9, what is it?
base
2Fe + 3O2 → 2Fe2O3
What process takes place, and what happens to mass?
A. Physical change; mass increases as rust forms.
B. Physical change; mass is conserved.
C. Chemical reaction; mass is conserved because reactant mass equals rust mass.
D. Chemical reaction; mass decreases because gas escapes.
C. Chemical reaction; mass is conserved because reactant mass equals rust mass.
What is the difference between an element and a compound?
What is a heterogeneous mixture?
A mixture of two or more substances that are not evenly distributed and can be easily distinguished
What is surface tension caused by?
cohesion where water molecules attract each other; molecules at the surface have stronger cohesion with the molecules around them, so the surface acts like a thin film
Which liquid would Jessica identify as a weak acid based on taste?
A. The sour liquid B. The salty liquid
C. The bitter liquid D. The sweet liquid
A. The sour liquid
The mass must be the same on both the reactant and products side OR the amount of atoms must be the same on both the reactant and products side
Homogeneous mixtures have _____.
- substances evenly distributed throughout
- more than one type of atom in the model
- are not chemically bonded together
TRUE OR FALSE: A compound is always a molecule but a molecule is not always a compound.
Why?
True.
Compounds are two or more different elements while molecules can be two or more different or similar elements (H2 is a molecule, but not a compound)
A needle floats on water. When Stacy adds soap, which separates water molecules, the needle sinks. Why? (explain with cohesion and surface tension)
Soap decreases the surface tension by decreasing the attraction between water molecules.
When a strong base is added to pure water, the pH will change and become ______ than the pH of pure water.
higher
When paper is burned, remaining ash mass is less than original paper
mass. Why?
A. Mass was destroyed during combustion.
B. The reaction was endothermic.
C. The ash is less dense than paper.
D. Some of the reaction products were given off as a gas.
D. Some of the reaction products were given off as a gas.
What are the elements involved? Will the mass be more, less, or stay the same after the chemical reaction?
2Al + 3CuCl2 --> 3Cu + 2 AlCl3
Stay the same