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Svetlanka [38]
2 years ago
14

If a rock sample has a half life of 10 years, and has 100 atoms of parent material today, how many half lives will have passed b

efore it has only 25 atoms of parent material left?
Biology
2 answers:
Lyrx [107]2 years ago
5 0

Answer:

1 half life, two half lifes to equal 25 atoms left

The 1 half life gets the amount of atoms to 50

2 half lifes gets the amount of atoms to 25.

Half life takes the amount of substance and halves it every certain amount of years.

NNADVOKAT [17]2 years ago
4 0

Answer:

<h2>1 half life,2 half life's to equals 25 atoms left.</h2>

<h2>The 1 half life gets the amount of atoms to 50.</h2>

<h2>Two half life's gets the amount of atoms to 25.</h2><h2>Half life's takes the amount of substance and Half's it every certain amount of years.</h2>
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Statements A, B and D are correct.

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3. 12:00 pm

Explanation:

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Which layers are impermeable ?
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A portion of an aquifer that contains rock material that does not allow water to penetrate; often forms the base of unconfined aquifers and the boundaries for confined aquifers.

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1-what are three ways organisms deal with limited resources
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1- Animals survive when they compete. In limited resources, animals either compete, kill or co-operat. There are 3 ways animals complete with each other to get access o limited resources. These ways are:

- Parasitism – In this relationship, one animal gets benefit and the other gets hurt.

- Mutualism – in this interaction, both organisms benefits each other and survives.

- Commensalism- In this interaction, one organism gets benefit whereas the other gets nothing in return.

2- Living organisms are classified as:

- Producers

- Consumers  

- Decomposers  

Producers are the energy generators. They are the biggest source of energy for other levels. Consumers feed on producers and other animals. And the end, when consumers die, decomposers feed on them, break down their bodies and mix it with soil increase its fertility and the cycle of energy flow goes on.


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Marcus discovered that sodium (Na) is found in Group 1, Period 3 on the periodic table. Where should Marcus look to find another
Leokris [45]

Answer:

1. A. Group 1

2. B. A chemical change occurred which is evidenced by the change in color of the solution.

3. D. Physical change because the chemical properties of the salt and water remained the same.

4. D. Sphere B will float because it is less dense than water.

5. C. Shredding them into smaller pieces.

6. A. Her model uses eleven white pom-poms.

   B. Her model uses twelve black pom-poms.

   E. Her model uses eleven yellow pom-poms.

7.  B. The liquids have different densities.

8.  D. Physical Properties: color, texture Chemical Properties: ability to rust

9.  A. Container A will have 1 liter of helium, and container B will have 1 liter of water.

Explanation:

1.

In the periodic table, <u>rows</u> represent the<em> period</em> that they are in, while columns represent the groups that elements are in. Elements in the same group (column) share similar properties. Since Sodium (Na) is found in group 1, elements that are similar in properties would be found in the same group.

2.  

A chemical change is marked with a change in color, production of gas, heat, and sometimes smell and light. A chemical change results in new products formed, in which the properties and identities of the reactants change as well because their atoms were rearranged. In this case, the <u>change in color </u>of solution shows that a chemical change had occurred.

3.

Earlier we said that chemical change results in new products, for physical change it does not. The substance will keep its identity. Like in the scenario, the salt and water did mix together, but when they were separated through evaporation, the salt <u>retained its identity</u> and so did the water. The substances involved merely changed phases. So this was a physical change.

4.

If the density of the object is more than the density of the liquid, the object will sink. On the other hand, if the density of the object is <u>less than the density of the liquid, it will float. </u>

If water has a density of 1g/cm³, the object that has the lesser density will float. First you solve for the densities of each object and it can be computed using the formula:

D = m/v

where D = density; m = mass; and v = volume

Sphere A:

d=\dfrac{m}{v} = \dfrac{24g}{19.4cm^3} = 1.23 g/cm^3

Sphere B:

d=\dfrac{m}{v} = \dfrac{13.6g}{17.0cm^3} = 0.8g/cm^3

So as you can see, only Sphere B has a density less or is less dense than water, so only Sphere B will float.  

5.

The groundskeeper shredding leaves is an application of physical change. As you can see, the identity of the leaves would be the same if you just shred them. Even if they change in shape and size, the leaves are still leaves, only smaller.

6.

A stable atom has the same number of electrons and protons. The number of protons is represented by the atomic number of an element.

Sodium has an atomic number of 11. This means that there are 11 protons (yellow pom poms) in a sodium atom. Since it is stable, you can also say that there are 11 electrons (White pom poms) as well.  

The number of neutrons can be determined by taking a look at the mass number of an atom. The mass number of sodium is 23. The mass number is the number of protons and neutrons combined.

23 = p + n

23 = 11 + n

23 - 11 = n

12 = n

The number of neutrons would be 12 (black pom poms).

7.

When two liquids do not mix, this means they are immiscible. The layers are formed because of the difference in density. Remember earlier about density and an object or substance's ability to float? Well it applies here too. The liquid on top is less dense than the one below it, so it floats up and the denser liquid sinks.

8.

Physical properties are things that you can observe using your senses. Chemical properties are properties that you can only observe when chemical structure is changed.

Seat cover has a <u>smooth texture. </u>  

Physical because it was determined by touch.

The front basket of the <u>bike is purple. </u>

Physical because it was determined by sight.

The <u>bike is rusted.</u>

Chemical because the metal changed its chemical structure as a result of a reaction.

9.

The sealed containers represent a closed system, or a vacuum where nothing goes in or out. In a closed system, just remember that matter is not created, nor destroyed. Simply put, this means that whatever it started with is what will it end up with.

In container A you have 1 L of helium gas, so since the container is sealed, none escaped. This means that you will end up with the same amount of helium gas as you did before. The same goes for the 1L of water in container B.  

7 0
2 years ago
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