By a black hole, the sky looks normal then the stars closer to the black holes look like they are spinning around the black hole.
The displacement, time, and direction
The complete statement is "chemical properties can be observed only when the substance in a sample of matter are changing into different substance".
It states a key concept in chemistry.
A chemical property is the ability of a substance, element or compound, to <em>transform</em> into other substances either <em>by decomposing or by combining</em> with one or more substances.
This transformation is defined as chemical reaction.
During chemical reactions some chemical bonds are broken and others are formed leading to the formation of one or more different substances called products.
Some examples of chemical properties are: reactivity with oxygen, reactivity with water, acidity, basicity, oxidation, reduction. The only way to tell if a substance has certain chemical property is by letting it react and so observe the change of the original substance into one or more different substances.
Question
What is the length of the pipe?
Answer:
(a) 0.52m
(b) f2=640 Hz and f3=960 Hz
(c) 352.9 Hz
Explanation:
For an open pipe, the velocity is given by
Making L the subject then
Where f is the frequency, L is the length, n is harmonic number, v is velocity
Substituting 1 for n, 320 Hz for f and 331 m/s for v then
(b)
The next two harmonics is given by
f2=2fi
f3=3fi
f2=3*320=640 Hz
f3=3*320=960 Hz
Alternatively, 
and 
(c)
When v=367 m/s then
