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In-s [12.5K]
3 years ago
9

How does a small set of elements combine to form molecules , compounds and mixtures, which are used in your daily lives?

Chemistry
1 answer:
Anastaziya [24]3 years ago
6 0

Elements are the simplest substances in nature that cannot be broken down into smaller parts by normal chemical means. They contain only atoms of the same type, ones that have identical chemical properties. There are at least 90 naturally-occurring elements, plus man-made ones. If you look at a periodic table, you'll see the names of each of these elements and some of their properties (such as mass, or how heavy the atom is).

Molecules & Compounds

When atoms from different elements are joined together in groups, they form molecules. The atoms in molecules bind together chemically, which means that the atoms cannot be separated again by physical means, such as filtration. The molecule has different properties from the elements from which is was made. A water molecule is not three separate atoms, two hydrogen (H) and one oxygen (O), but it is actually a unique H2O molecule with its own set of distinct properties.

Like elements that are formed of atoms of the same sort, compounds are formed of molecules of the same sort. The elements can be combined into about 2 million different compounds! Did you know that eggshells are made up of a calcium carbonate compound? And citric acid, which is found in oranges and other citrus fruit, is a compound of carbon, hydrogen, and oxygen atoms. Your kids might find it helpful to do a science research project finding other common compounds around your house. Make hypotheses and do research using a chemistry reference book, web site, or text book to find out the answers.

There are more carbon compounds than compounds of any other element. Organic compound is the name for the carbon compounds found in all living things.

Mixtures - A Bit of This and That

All matter can be classified into two categories: pure substances and mixtures. A pure substance consists of a single element or compound. Iron is formed only of iron (Fe) atoms; table salt is formed only of sodium chloride (NaCl) molecules. A mixture, however, is made up of different compounds and/or elements. When salt is added to water to make saltwater, it becomes a mixture. The salt and water molecules do not combine to form new molecules, but only "mix" together while still retaining their identities. Air is also a mixture, containing just the right amounts of nitrogen, oxygen, and other gases for life on Earth.  

Not all mixtures have the same composition throughout. Salt water does, but Italian salad dressing does not--the parts separate and are not perfectly blended or homogenous. Mixtures of metals are called alloys (bronze is an alloy of copper and tin); liquid mixtures (such as saltwater) are called solutions.

The substances that make up a mixture can be separated by physical means because they have different physical properties (such as different melting points) and are not chemically bonded. A mixture can be separated into its parts in a variety of ways, including decantation (letting the sand in a mixture of water and sand settle, and then draining off the water, for example), filtering, and evaporation. You can use a kitchen funnel and coffee filter for filtration, and either use sunlight or low heat for evaporation. Try out these methods on saltwater and a sand and water mixture to see how they work and compare the results. Evaporation will work for both saltwater and sand and water solutions, but filtration will not work for saltwater. Can you think of other examples where a separating method will work for one mixture and not another? Another one to try is lemon juice, a mixture of water and citric acid; what do you think happens when it is boiled? The water evaporates and eventually leaves nothing but citric acid crystals

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If 12.5 grams of the original sample of cesium-137 remained after 90.6 years, what was the mass of the original sample?
myrzilka [38]

Answer:

Mass of original sample = 100 g

Explanation:

Half life of cesium-137 = 30.17 years

t_{1/2}=\frac {ln\ 2}{k}

Where, k is rate constant

So,  

k=\frac{\ln2}{t_{1/2}}

k=\frac{\ln2}{30.17}\ year^{-1}

The rate constant, k = 0.02297 year⁻¹

Time = 90.6 years

Using integrated rate law for first order kinetics as:

[A_t]=[A_0]e^{-kt}

Where,  

[A_t] is the concentration at time t

[A_0] is the initial concentration

Initial concentration [A_0] = ?

Final concentration [A_t] = 12.5 grams

Applying in the above equation, we get that:-

12.5\ g=[A_0]e^{-0.02297\times 90.6}

[A_0]=\frac{12.5}{e^{-0.02297\times 90.6}}\ g=100\ g

<u>Mass of original sample = 100 g</u>

8 0
3 years ago
How are elements and compounds related
Lisa [10]
Elements are a one of a class of substances that cannot be seperwted into simpler substances by chemicalk means. Compounds is a substance formed when two or more chemical elements are chemically bonded together. Relation: When two elements or more are formed chemically together its called a compound without elements there won't be compounds and without compounds there won't be elements.
5 0
3 years ago
Write a balanced chemical equation for the reaction that occurs when heptane, C7H16(l) , burns in air.
Pavlova-9 [17]
Start with Unbalanced Equation and balance it, so...
C7H16+O2--->CO2+H2O
There are 7 C atoms on the left-hand side, so we need 7 C atoms on the right-hand side. Add a 7 in front of the CO2...7CO2+H2O on right side now.
We have fixed 16 H atoms on the left-hand side, so we need 16 H atoms on the right-hand side. Add an 8 in front of H2O to make 16 (8x2)...7CO2+8H2O on right side now.
There are 22 O atoms on the right-hand side: 14 from the CO2 and 8 from the H2O. Add an 11 in front of the O2 on the left side to make 22 (11x2).
Every formula now has a fixed coefficient. You should have a balanced equation of...
C7H16+11O2--->7CO2+8H2O
8 0
3 years ago
Why estuaries are an important habitat for many marine organisms in comparison to the open ocean?
Alexxandr [17]

Answer:

There are more nutrients available in estuaries. There are more nutrients available in estuaries.

Explanation:

5 0
3 years ago
Xa4D6A/viewform?hr_submission=ChglisyXkhUSEAj9|d2MkQsSBwjg24qS6woo
Juli2301 [7.4K]
It’s should be option 4
4 0
3 years ago
Read 2 more answers
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