Answer:
The change of state of wax from solid to liquid and liquid to vapors is a physical change.
Explanation:
Physical Change
The changes that occur only due to change in shape or form but their chemical or internal composition remain unchanged.
These changes were reversible.
They have same chemical property.
These changes can be observed with naked eye.
Chemical:
The changes, that occur due to change in the composition of a substance and result in a different compound is known as chemical change.
These changes are irreversible
.
These changes occur due to chemical reactions.
These may not be observed with naked eye
Example
When a candle is burned, the both physical and chemical changes occur.
The solid wax is melted into the liquid and than liquid is evaporated into vapor form. It is a physical change because just the state of mater is changed. When vapors of wax are react with oxygen in air and form carbon dioxide and ash it is a chemical change which can not be reversed.
Answer:
D. One dependent variable and one experimental variable
Explanation:
The experimental variable is defined as an independent variable which can be manipulated during an experiment in order to find out its impact or influence on the dependent variable.
The dependent variable refers to a variable that changes when an experimental or independent variable is manipulated.
Every experiment must have at least one experimental variable and one dependent variable in order to yield any meaningful result.
Answer:
2 significant figures i.e. 2 and 7.
Explanation:
We need to find the number of significant figures in the given number i.e. 
.
It has 2 significant figures i.e. 2 and 7.
It means the power of 10 doesn't count in the significant figures.
Hence, there are 2 significant figures.
T is the time it takes for one complete oscillation , it is measured in seconds. All waves, including sound waves and electromagnetic waves , follow this equation. For example, a wave with a time period of 2 seconds has a frequency of 1 ÷ 2 = 0.5 Hz. A sound wave has a time period of 0.0001 seconds.
