Heat energy is necessary for evaporation to occur. Energy is used to break the bonds that hold water molecules together, which is why water easily evaporates at the boiling point. In fact the process of the evaporation removes heat from the environment . Which of these every day examples illustrates how evaporation removes heat from the environment ?

Answer:

b

Explanation:

Answer:

(NH4)2CO3 is the formula !

Answer:

[tex](NH_4)_2CO_3[/tex]

Explanation:

Ammonium carbonate is made by reacting ammonium sulfate, ammonium chloride, and calcium carbonate in a furnace.

Given :

Measurements [tex]4.5\ cm\times 2000.0\ cm\times 4\ cm[/tex] .

To Find :

The multiplication using significant figures .

Solution :

We know , the least number of significant figures in any number of the problem determines the number  of significant figures in the answer.

So , significant figure( S.F) in 4.5 cm is 2 .

S.F in 2000.0 cm is 5 .

S.F in 4 cm is 1 .

So , minimum S.F is 1 .

Therefore , S.F of their product is 1 .

Now , multiplying them we will get :

[tex]M=4.5\times 2000.0\times 4 \ cm^3\\\\M=36000\ cm^3[/tex]

Now , converting 36000 in 1 significant digit .

First we will write it in exponential 2 S.F form.

[tex]3.6\times 10^4 \ cm^3[/tex]

Now , to convert 3.6 into 1 S.F we should round off this .

So , round off 3.6 we will get 4 .

Therefore , The multiplication using significant figures is [tex]4\times 10^4\ cm^3[/tex] .

Hence , this is the required solution .

Answer:

A substance made from 2 or more elements is called a compound

Answer:

the volume of water with egg was 200 and when we removed the egg become 125

Explanation:

200ml - 125ml = 75ml

so 1 millimeter = 1 centimeter cubic

so

75ml = 75 cm3

the answer is 75cm3

Answer:

When  wood is burnt , it turns into ashes which is a new substance and process is irreversible one,( chemical change)

When wood is cut into smaller pieces (firewood) this is a physical change

Explanation:

Answer:

Electrons are the smallest of the particles that make up an atom, and they carry a negative charge. The number of protons and electrons is equal in a neutral atom. The hydrogen atom, for example, has just one electron and one proton. The uranium atom, on the other hand, has 92 protons, and therefore, 92 electrons.

Answer:

communicating results

Explanation:

Answer:

Communicating results

Explanation:

Answer:

The answer to this is simple.  

There is a school of thought that believes that natural fires are necessary.

Explanation

They are required to reduce the density of the forests that are so thick that when they eventually burn, the effects are usually catastrophic. According to one source, some of these forests are over a hundred years old. When eventually these kinds of forests catch fire, they become very hard to manage and the destruction the leave are usually worse off than if they had not been allowed to so heavy and impenetrable.  

Another reason put forward by this school of thought is that the countries who own these forests have politicised wildfires using them as an excuse to attract international funding/assistance because the fires are depleting the worlds protective greenery/earth biggest natural oxygen factory.

Cheers!

Answer:

protons and neutrons located within the nucleus, with electrons in orbitals surrounding the nucleus.

Answer:

Explanation:

Density of a substance can be found by using the formula

[tex]Density(\rho) = \frac{mass}{volume} [/tex]

From the question

Density = 2.5 g/mL

volume = 20 mL

To find the mass substitute the values into the above formula and solve for the mass

That's

Making mass the subject we have

mass = Density × volume

mass = 2.5 × 20

We have the final answer as

Hope this helps you

Answer:

mass=?,volume=20,density=2.5.

density=mass/volume.

which will be 2.5=mass/20

which is mass=2.5×20=50kg

Answer:

There is only 1 sig figures in 6

Explanation:

There is no 0 after it so it is considered as only 1 significant figure

Answer:

Compound

Explanation:

Consisting mostly of sugar dissolved in water (corn syrup), and having the same concentration of solute throughout, it would be classified as homogeneous. Are compounds heterogeneous or homogeneous?

Cough syrup is a mixture as more than one compound is used in it. It is a homogenous mixture.

A mixture is a material made up of two or more different chemical substances which are not chemically bonded. A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions and colloids.

A mixture can be homogenous mixture or heterogenous mixture. Homogenous mixture is a mixture in which there are more that one components but we can't distinghuish them with our eye whereas heterogenous mixture is a mixture in which there are more that one components and we can distinghuish them with our eye.

Traditional cough mixtures are formulated around a syrup at 60 - 75% concentration which is made from sucrose, maltodextrin, glucose, invert syrup, etc. The remainder is made up of thickening agents, stabilizers and active ingredients.

Therefore, Cough syrup is a mixture as more than one compound is used in it. It is a homogenous mixture.

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#SPJ2

Answer:  x=13/3

Explanation:

step 1: multiply both sides by 10: 36x=6x+130

step 2: subtract 6x from both sides 30x=130

step 3: divide both sides by 30: x=13/3

Answer:

A. Carbon

B. I, III

Explanation:

Carbon has four valence eletrons meaning that it is more stable than the other choices. A proton has mass and has a positive charge.

Answer:

Center for Disease Control (CDC)

Explanation:

All of the other answers can be changed and may not be backed with actual scientific evidence.

Answer:

CDC

Explanation:

(1) Islands are always surrounded by bodies of water, in this case oceans. These islands tend to have more 'stable climates' and 'smaller temperature fluctuations' due to the specific heat of water, which is quite high, 4180 J/kg C. The higher the specific heat, the more the energy needed to raise the temperature of the substance. Land requires less energy to raise it's temperature than water due to it's lower specific heat. Thus, islands tend to have more stable temperatures than regions surrounded by land.

(2) Based on the conditions provided, the thermochemical equation for the reaction should be:  

2NaHCO₃ (s) ---> Na₂CO₃ (s) + H₂O (g) + O₂ (g)

This is a decomposition reaction, as it explains that the baking soda breaks down into the products. All we had left to do is balance the equation, adding 2 as the coefficient of the reactant.

(3) Let's rewrite the given equations:

First chemical reaction: H₂(g) + F₂(g)  ---> 2HF(g), ΔH₁ = –537 kJ.

Second chemical reaction: C(s) + 2F₂(g) ---> CF₄(g), ΔH₂ = –680 kJ

Third chemical reaction: 2C(s) + 2H₂(g) ---> C₂H₄(g), ΔH₃ = +52.3 kJ.

Fourth chemical reaction: C₂H₄(g) + 6F₂(g) ---> 2CF₄(g) + 4HF(g), ΔH₄ = ?

Now the 'fourth chemical reaction' is the one in which we need to determine the enthalpy:

ΔH₄ = 2(ΔH₁) + 2(ΔH₂) - ΔH₃,

ΔH₄ = 2(–537) + 2(–680) - 52.3 = -2486.3 kJ

Answer:

can we see the type that is shown?

Answer:

(a) (i) 44

(ii) 88 and 36

(iii) 2.2

(b)H₂–C=C–H₂

Answer:

What are Variables?

Scientists try to figure out how the natural world works. In doing so, they use experiments to search for cause and effect relationships. Cause and effect relationships explain why things happen and allow you to reliably predict what will happen if you do something. In other words, scientists design an experiment so that they can observe or measure if changes to one thing cause something else to vary in a repeatable way.

The things that are changing in an experiment are called variables. A variable is any factor, trait, or condition that can exist in differing amounts or types. An experiment usually has three kinds of variables: independent, dependent, and controlled.

The independent variable is the one that is changed by the scientist. Why just one? Well, if you changed more than one variable it would be hard to figure out which change is causing what you observe. For example, what if our scientific question was: "How does the size of a dog affect how much food it eats?"; then, during your feeding experiments you changed both the size of the dog and the time of day the dogs were fed. The data might get a bit confusing— did the larger dog eat less food than the smaller dog because of his size or because it was the middle of the day and dogs prefer to eat more in the morning? Sometimes it is impossible to just change one variable, and in those cases, scientists rely on more-complicated mathematical analysis and additional experiments to try to figure out what is going on. Older students are invited to read more about that in our Experimental Design for Advanced Science Projects page. To be clear though, for a science fair, it is usually wise to have only one independent variable at a time. If you are new to doing science projects and want to know the effect of changing multiple variables, do multiple tests where you focus on one independent variable at a time.

The dependent variables are the things that the scientist focuses his or her observations on to see how they respond to the change made to the independent variable. In our dog example, the dependent variable is how much the dogs eat. This is what we are observing and measuring. It is called the "dependent" variable because we are trying to figure out whether its value depends on the value of the independent variable. If there is a direct link between the two types of variables (independent and dependent) then you may be uncovering a cause and effect relationship. The number of dependent variables in an experiment varies, but there can be more than one.

Experiments also have controlled variables. Controlled variables are quantities that a scientist wants to remain constant, and she or he must observe them as carefully as the dependent variables. For example, in the dog experiment example, you would need to control how hungry the dogs are at the start of the experiment, the type of food you are feeding them, and whether the food was a type that they liked. Why? If you did not, then other explanations could be given for differences you observe in how much they eat. For instance, maybe the little dog eats more because it is hungrier that day, maybe the big dog does not like the dog food offered, or maybe all dogs will eat more wet dog food than dry dog food. So, you should keep all the other variables the same (you control them) so that you can see only the effect of the one variable (the independent variable) that you are trying to test. Similar to our example, most experiments have more than one controlled variable. Some people refer to controlled variables as "constant variables."

In the best experiments, the scientist must be able to measure the values for each variable. Weight or mass is an example of a variable that is very easy to measure. However, imagine trying to do an experiment where one of the variables is love. There is no such thing as a "love-meter." You might have a belief that someone is in love, but you cannot really be sure, and you would probably have friends that do not agree with you. So, love is not measurable in a scientific sense; therefore, it would be a poor variable to use in an experiment.

Answer:

c

Explanation:

Answer:

c

Explanation:

Answer:

Refraction of waves involves a change in the direction of waves as they pass from one medium to another,so as water waves are transmitted from deep water into shallow water,the speed decreases,the wavelength decreases and the direction changes

Answer:

See explanation

Explanation:

Even though the options were not stated in the question, it is clear that the prediction required must reflect the stated fact that the sublimation temperature of CO2 is -78.5°C. This is the fact that was observed in the cause of the experiment. Hence any of the options that reflects this statement must be the correct option among the list of options available in the question.

Answer:

Formation of a dative bond or coordinate bond between ammonia and boron trifluoride. When the nitrogen donates a pair of electrons to share with the boron, the boron gains an octet. Both atoms are electronically saturated.

Explanation:

Answer:

When you are dealing with any chemicals it is important to identify the chemical first and then look up the chemical safety data sheet. The safety data sheet will identify all the proper personal protective equipment to be worn when handling that chemical. Most chemicals require protective splash proof eye wear, chemical resistant gloves and a chemical resistant apron. It would also be recommended to wear closed toed shoes and maybe even a face shield in case of a violent reaction if chemicals are to be mixed. There is always a concern using a Bunsen burner and a person should use the appropriate lifting tools in order to prevent burns from moving hot beakers and the burner itself.

Explanation:

Three families are found in the center portion of the periodic table are of iron, cobalt and nickel atoms.

Groups are the vertical columns of elements present in the periodic table in which elements of same valency and valence configuration is present.

In the periodic table total 18 groups are present starting from left side to right side. In the middle of the periodic table three families or groups of iron, cobalt and nickel atoms are present which are known by the name of group 8th, 9th and 10th of the periodic table.

So, three families are of iron, cobalt and nickel atoms.

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Answer:

skin

Explanation:

I think its skin because there is a protein that mostly makes up our skin, called keratin.