What other signs provide evidence of chemical reactions and show that a chemical change has occurred?

QUESTION POSTED AT 13/02/2020 - 04:55 PM

Answered by admin AT 13/02/2020 - 04:55 PM

Color change
new substance formed
heat or light change
new smell
irreversible 
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Related questions

Question 1 what happens during a neutralization reaction?

A neutralization reaction is when an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water. The neutralization of a strong acid and strong base has a pH equal to 7.

  • New substances called SALTS and water are formed in neutralization reactions.
  • For example, hydrochloric acid and sodium hydroxide solution react together to form water and sodium chloride solution. The H+ ions and OH– ions produce the water, and the Na+ ions and Cl– ions produce the sodium chloride, NaCl(aq).

ANSWERED AT 28/02/2020 - 05:11 PM


QUESTION POSTED AT 28/02/2020 - 05:11 PM

Every chemical reaction involves a change in

A chemical reaction is when you cant change something back to the way it was before 

ANSWERED AT 28/02/2020 - 05:09 PM


QUESTION POSTED AT 28/02/2020 - 05:09 PM

What is the change of state from solid to liquid called?

It is melting point process

ANSWERED AT 28/02/2020 - 05:02 PM


QUESTION POSTED AT 28/02/2020 - 05:02 PM

Based on the observational evidence, is it possible that dark matter doesn't really exist

Dark matter has been given this name because it doesn’t seem to interact with regular matter in any way. It doesn’t collide with it, or absorb energy from it. We can’t see it or detect it with any of our instruments. We only know it’s there because we can see the effect of its gravity.

ANSWERED AT 28/02/2020 - 04:44 PM


QUESTION POSTED AT 28/02/2020 - 04:44 PM

Amino acids cannot be broken down to provide energy.

False, Dietary proteins are first broken down to individual amino acids by various enzymes and hydrochloric acid present in the gastro-intestinal tract. These amino acids are further broken down to α-keto acids which can be recycled in the body for generation of energy, and production of glucose or fat or other amino acids.

ANSWERED AT 28/02/2020 - 04:42 PM


QUESTION POSTED AT 28/02/2020 - 04:42 PM

What is the chemical symbol for nitrogen and oxygen?

N2 and O2

hope it helps

ANSWERED AT 28/02/2020 - 04:26 PM


QUESTION POSTED AT 28/02/2020 - 04:26 PM

What happens to the temperature of water between the time ice melts and water boils (this is partially quoted from a question)? Also, what change occurs in temperature after water starts boiling (this is also from a booklet)? Thank you and please explain your thoughts. This is based on the phase changes of water, and you should refer to a graph on the phase changes of water.

Your first statement is very ambiguous so I will give it the best shot as to what you are saying.
The temperature, between the point of ice melting and water boiling, is increasing as water is in its liquid state.
Now during a phase change, or while the water is boiling, the temperature remains constant because the energy being added is being consumed to complete the phase change.
But if you're looking at the phase change graph, the points of positive slopes, are moments when energy is increasing as the water, in whatever state, is increasing. But when the slope of the graph is 0, the water is changing phases and the temperature remains constant! I hope I explained that so you could understand it, and I hope this helps you!

ANSWERED AT 28/02/2020 - 03:47 PM


QUESTION POSTED AT 28/02/2020 - 03:47 PM

What chemical is in plastic bottle and how it affect humans?

BPA, or bisphenol A, is in most plastics and it is toxic to humans because it can bind to the estrogen hormone and greatly alter your body's natural functions from there. It can also bind to your thyroid hormone.

ANSWERED AT 28/02/2020 - 03:44 PM


QUESTION POSTED AT 28/02/2020 - 03:44 PM

Write the symbol for every chemical element that has atomic number less than 74 and atomic mass greater than 173.8u

You should be able to locate them on the periodic table as long as you know which part the atomic number is and which part the atomic mass is.

ANSWERED AT 28/02/2020 - 03:22 PM


QUESTION POSTED AT 28/02/2020 - 03:22 PM

What chemicals are released by burning oil, and how are they harmful?

Carbon dioxide, carbon monoxide, lead, nitrogen oxides, particulate matter, polycyclic aromatic hydrocarbons, sulfur dioxide , and volatile organic compounds.
They are harmful to human health.

ANSWERED AT 28/02/2020 - 03:11 PM


QUESTION POSTED AT 28/02/2020 - 03:11 PM

Classify this chemical equation as a combination/synthesis , decomposition, single replacement, double replacement, or combustion. Pb(s) + Hg2SO4(s) --> PbSO4(s) +2 Hg(l)

S is for soil,cl (sometimes c) represents climate,o organisms including humans,r relief,p parent material, or lithology, andt time.

ANSWERED AT 28/02/2020 - 03:10 PM


QUESTION POSTED AT 28/02/2020 - 03:10 PM

Describe four ways you could increase the rate of a chemical reaction.

1. Increase the temperature  

2. Increase the pressure of an reacting gas  

3. Solid reactants are broken into smaller pieces

4. The concentration of a dissolved reactant is increased.

ANSWERED AT 28/02/2020 - 03:06 PM


QUESTION POSTED AT 28/02/2020 - 03:06 PM

During a chemical reaction, energy is converted from one form to another increases decreases is used up as bonds are broken and formed

Is used up as bonds are broken and formed .

ANSWERED AT 28/02/2020 - 03:02 PM


QUESTION POSTED AT 28/02/2020 - 03:02 PM

Which of the following is not one of the three ingredients needed to form a cloud? dust or solid matter of some sort water molecules wind temperature and pressure changes

I think is wind(not needed in the formation of cloud).

ANSWERED AT 28/02/2020 - 02:57 PM


QUESTION POSTED AT 28/02/2020 - 02:57 PM

The specific heat of nickel is 0.44 J/g*⁰C. How much energy needed to change the temperature of 95.4g of nickel from 22⁰C to 32⁰C. Is the energy absorbed or released?

Answer : The amount of energy needed is, 419.76 J and the energy is absorbed.

Solution :

Formula used :

Q=m\times c\times \Delta T=m\times c\times (T_{final}-T_{initial})

where,

Q = heat gained or absorbed = ?

m = mass of nickel = 95.4 g

c = specific heat of nickel = 0.44J/g^oC      

\Delta T=\text{Change in temperature}  

T_{final} = final temperature = 32^oC

T_{initial} = initial temperature = 22^oC

Now put all the given values in the above formula, we get

Q=95.4g\times 0.44J/g^oC\times (32-22)^oC

Q=419.76J

The value of Q is positive that means energy is absorbed.

Therefore, the amount of energy needed is, 419.76 J and the energy is absorbed.

ANSWERED AT 28/02/2020 - 02:51 PM


QUESTION POSTED AT 28/02/2020 - 02:51 PM

What type of reaction is radioactive decay? 1zero order 2first order 3second order 4third order

2. first order reaction
Hope I helped! :)

ANSWERED AT 28/02/2020 - 02:46 PM


QUESTION POSTED AT 28/02/2020 - 02:46 PM

How does a change in medium affect light?BTW, If you have any extra questions ask for details, don't steal points please.

The speed of light changes as it passes from one medium to another medium due to the difference in the density of the two media. This is the reason for refraction of light also.

ANSWERED AT 28/02/2020 - 02:41 PM


QUESTION POSTED AT 28/02/2020 - 02:41 PM

How has telephones change over time

Telephones began as large, clunky devices capable of transmitting and receiving voice messages over short distances, then evolved to lighter, transportable cellular devices capable of enabling communications over large distances. In the United States, Alexander Graham Bell receives credit for producing the first telephone in 1876. Bell established a basic system of communications allowing people to talk with each other remotely over short distances through receivers. As with other technologies, phone technologies improved dramatically and rapidly following Bell's introduction of the telephone to American life. In addition to improvements in the device itself, transmissions methods improved as well. By 1900, telephone companies established communication lines through many American cities, allowing people to connect over larger distances. These lines contained special coils to reduce static and expedite transmissions. Telephone calls remained limited to local regions within the borders of the United States through 1915. Then, Alexander Graham Bell completed the first transcontinental call with Thomas Watson. Rotary phones emerged just before 1920, and a numbering plan arrived in the late 1940s to allow fast and direct connections between callers. In 1956, telephone cables permitted transcontinental calls for the first time. In the 1960s and 1970s, phone use extended to emergency service and the military. Portable phones arrived in the early 1970s; by 2000, thousands of Americans carried lightweight, compact phones wherever they went. AND THEY HAVE IPHONES NOW XDD

ANSWERED AT 28/02/2020 - 02:36 PM


QUESTION POSTED AT 28/02/2020 - 02:36 PM

How manyy grams of h2 are needed to react with 20 grams of o2. please show work

Would it be 10, you know 1h for every 2o, H2O


ANSWERED AT 28/02/2020 - 02:28 PM


QUESTION POSTED AT 28/02/2020 - 02:28 PM

If 4 mol 02 are used , how many moles of h2 are produced. please show work

There is a 2:1 ratio between H2 and O2.  so for every mol of O2 used there would be 2 mol needed, so if we use 4 mol of O2 we multiply 4 by 2 to get 8 mol of H2 used in this reaction

ANSWERED AT 28/02/2020 - 02:26 PM


QUESTION POSTED AT 28/02/2020 - 02:26 PM

When you do a displacement reaction with iron and copper what is the orange metal called

It is called rust and it forms when water soaks into the metal forming a chemical reaction.

ANSWERED AT 28/02/2020 - 02:21 PM


QUESTION POSTED AT 28/02/2020 - 02:21 PM

What happens during a neutralization reaction?

Protons and hydroxide combined to create water molecules while the remaining ions.

ANSWERED AT 28/02/2020 - 02:17 PM


QUESTION POSTED AT 28/02/2020 - 02:17 PM

What are two ways the study of fossils helps add to our understanding of the changes in Earth's environments?

They help us understand the concept of evolution and they help us understand what our earth was like before and after pangea or the great continental drift

ANSWERED AT 28/02/2020 - 01:37 PM


QUESTION POSTED AT 28/02/2020 - 01:37 PM

Causes rocks to change composite when reacting with oxygen

The steel in nail contains iron. Oxygen and water react with the iron to form rust. (oxidation i believe. i may be wrong) 
Minerals in rocks undergo chemical changes when they react with water and air. is the breakdown of rocks by chemical reactions that change the rocks' makeup, or composition.

ANSWERED AT 28/02/2020 - 01:29 PM


QUESTION POSTED AT 28/02/2020 - 01:29 PM

5 ways weathering can occur

Rain, plant roots, tempeture, biological acivity 

ANSWERED AT 28/02/2020 - 01:05 PM


QUESTION POSTED AT 28/02/2020 - 01:05 PM