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choli [55]
3 years ago
12

What is a Pure element ?

Chemistry
1 answer:
inn [45]3 years ago
4 0
A substance where almost all have the same atomic number of protons
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Some chemical factories make hydrogen gas (H2) using a process called steam methane reforming. In this process, methane (CH4) co
erica [24]

Answer:

steam and methane

Explanation:

5 0
3 years ago
if matter is made of many tiny particles, why does it seem to be continuous? Why doesn’t water seem to behave like sand?
valkas [14]

Answer:

Explanation:

if matter is made of many tiny particles, why does it seem to be continuous? Why doesn’t water seem to behave like sand?

Water and some other molecules exhibit a property know as hydrogen bonding.  A hydrogen atom in one molecule of water is attracted to the oxygen in a neighboring molecules of water.'

The force of this attraction is less than a standard chemical attractive force, but it is real and measurable.

When billions and trillions of water molecules are held together by this force, the small amount of molecule to molecule force is added up to a tremendous force.  That is why even though sulfur is below oxygen on the periodic table, hydrogen sulfide is a gas while hydrogen oxide is a liquid at room temperature.

Hydrogen bonding explains the unique properties of ice, liquid water and steam,We all know water exists in several forms such as solid, liquid and ice. Water boils at 100  C and freezes at 32  F, right? Am I correct? Let us look at some of the chemistry behind forms of water.  

The strong polar bond between water molecules creates water cohesion.

As they are cooled, aggregates of most other substances increase monotonically in density becoming progressively heavier -- the colder they are, the more tightly packed their molecules become. But water possesses a peculiar physical feature: ice expands, so it is lighter than liquid water (i. e., ice floats). When water trapped in rock crevices freezes, it breaks rocks (and pipes).

 

Water is vital to all known life forms, that is, all those on planet Earth. It is so integral to life as we know it that many biologists cannot even envision life without water (although that might be possible). Indeed, the physical properties of water dictate critical thermal limits for living systems.

In one sci-fi story, an alien refers to humans as "ugly bags of mostly water" -- our bodies are about 60-70% water, depending upon how dehydrated we are at any given time. Humans use massive amounts of freshwater to drink, cook, bathe, flush toilets, do laundry, fill swimming pools, irrigate yards and gardens, run flowing fountains, and for recreation. Precious clean water is often wasted, such as when people leave tap water running while washing their hands or brushing their teeth. The personal water consumption of an average American is about 200 gallons per day, but when industrial and energy usage is added in, per capita freshwater usage is more than 2000 gallons/day. People in third world countries use much less water, of course.

Most freshwater is claimed or "owned" and there is not enough to go around. Approximately half of the world's population of people do not even have adequate access to clean drinking water. One of the major symptoms of the human overpopulation crisis is shortages of available fresh water. Wars will be fought over water.

7 0
2 years ago
How many significant figures are needed in the answer when 1.31m is multiplied by 6.5 m​
dmitriy555 [2]

Answer:

two

Explanation:

The number of significant figures needed in the answer is 2.

This is because when finding the products of two numbers, the result is as accurate as the least number of significant figures of the numbers being multiplied.

Here the numbers being multiplied are;

 1.31m

 6.5m

        1.31m has 3 significant figures

          6.5m has 2 significant figures.

So, the product will have 2 significant figures

6 0
3 years ago
2. A quantity of 1.922g of methanol (CH3OH) was burned in a constant-volume
Cerrena [4.2K]
Mass of methanol (CH3OH) = 1.922 g
Change in Temperature (t) = 4.20°C
Heat capacity of the bomb plus water = 10.4 KJ/oC
The heat absorbed by the bomb and water is equal to the product of the heat capacity and the temperature change.
Let’s assume that no heat is lost to the surroundings. First, let’s calculate the heat changes in the calorimeter. This is calculated using the formula shown below:
qcal = Ccalt
Where, qcal = heat of reaction
Ccal = heat capacity of calorimeter
t = change in temperature of the sample
Now, let’s calculate qcal:
qcal = (10.4 kJ/°C)(4.20°C)
= 43.68 kJ
Always qsys = qcal + qrxn = 0,
qrxn = -43.68 kJ
The heat change of the reaction is - 43.68 kJ which is the heat released by the combustion of 1.922 g of CH3OH. Therefore, the conversion factor is:
5 0
3 years ago
Uranium – 235 has a half-life of 713 million years. Would uranium – 235 or carbon – 14 be more useful for dating Cambrian time e
kenny6666 [7]
Uranium-235 would be more useful for dating in Cambrian time because Cambrian time was 540 million years ago while the half life of carbon-14 is only 5,730 years
Hope this helps
6 0
3 years ago
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