Chemistry Test

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Checked CHEMISTRY TEST DATE:9/11/15 Q1: How are solids, liquids and gases arranged? 0/2 ANS: In solid, particles are tightly packed with one another and their particles are not free to move. In liquids, particles are not as tightly packed with one another .Their particles are less dense than solids and they are free to move from one place to another. Gas particles are not loosely packed; they are lying from one place to another and are very free to move from one place to another. Answer is plagiarized (Re-write) Q2: what is condensation, sublimation, freezing, melting and boiling? 2/3 ANS: When the state of gas changes to liquid it is is called condensationing. When solid directly changes from solid to gas instead of liquid is called sublimation. When liquid is freeze, the liquid changes into solid. The change of state from solid to liquid is called melting.

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Transcript of Chemistry Test

Page 1: Chemistry Test

Checked

CHEMISTRY TEST

DATE:9/11/15

Q1: How are solids, liquids and gases arranged? 0/2

ANS: In solid, particles are tightly packed with one another and their particles are not free to move. In liquids, particles are not as tightly packed with one another .Their particles are less dense than solids and they are free to move from one place to another. Gas particles are not loosely packed; they are lying from one place to another and are very free to move from one place to another. Answer is plagiarized (Re-write)

Q2: what is condensation, sublimation, freezing, melting and boiling? 2/3

ANS: When the state of gas changes to liquid it is is called condensationing.

When solid directly changes from solid to gas instead of liquid is called sublimation.

When liquid is freeze, the liquid changes into solid.

The change of state from solid to liquid is called melting.

When liquid is changing into gas is called boiling.

Q3: how does diffusion take place? 1/2

ANS: Diffusion is travelling of something mixed with air from one place to another. Diffusion is mainly held in gas, liquid particles diffuse less and solid cannot diffuse in any way.

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Q4. In a typical experiment, the white ring of ammonium chloride take a little time to form. Why? 1/2

ANS: White ring takes little time to form because of more temperature while there is more diffusion in more temperature. (answer not clear, Re-werite)

Q5: What are isotopes? Name any 2 isotopes 2/2

ANS: Isotopes are like neighbor element of one element. Their number of neutrons varies slightly. The number of protons is same but different numbers of neutron.

E.g.: Carbon 12, Carbon 13

Q6. How are electrons arranged in an atom? 0/1

ANS: Electrons are arranged on the levels outside the nucleus called shells or energy levels. (answer plagiarized, Re-phrase)

Q7. Draw the arrangement of a carbon atom? 2/2

ANS: There are 6 electrons in carbon so (2, 4). First we will make two circles that are energy levels and in first energy level we will put 2 electrons and in second energy level we will put 4 electrons. (good effort)

Q8. What does the group arrangement in the periodic table show? Give 3 examples. 0/2

ANS: Group arrangement shows from which group the element belongs. (Wrong answer)

E.G. : lithium is in group I , magnesium is in group II , helium is in group VIII

Q9. What is the difference between mass number and atomic number? 2/2

ANS: Atomic number is the number of protons and mass number is the number of protons and neutrons.

Q10. Explain with an example for each the 3 types of bonding?

ANS: There are three types of bonding. 3/3

IONIC: In ionic bonding electrons are donated and gained by atoms and they become ion.

E.G: NA+CL-

COVALENT: In covalent bonding electrons are shared between each other.

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E.G: H2

METALLIC: In metallic bond there are delocalized electrons that are free to move and then they lie down and metal becomes positive. Metals always contain positive ion.

E.G: Copper

Q11. Why does hydrogen form molecules? 1/1

ANS: Hydrogen forms molecules because they are covalent compounds, two hydrogen atoms are shared between each other. Hence the formula is h2.

Q12. What is a anion and cation? 1/1

ANS: Anion is a negatively charged atom and cation is a positively charged atom.

Q13. What are intermolecular forces? 2/2

ANS: Every molecule, ion or atom have intermolecular forces .They are neighbor forces and if intermolecular forces are strong then the bond will be also strong. If the bond has to be broken the intermolecular forces should also have to be broken.

Q14. What is the difference between an atom and an ion? 1/1

ANS: Atom with neutral charge is called an atom and atom with any charge called ion.

Q15. Why are metals good conductors of heat and electricity? 1/3

Metals are good conductor of electricity and heat because of delocalized electrons. (Not well explained, needs a brief explanation- explain it)

Q16. Why are metals usually elastic? 0/2

Metals are elastic because they can be easily shaped in any way. (Wrong answer)

Q17. What are alloys? 2/2

ANS: A mixture of different metals is called alloy. Metals are alloyed with other metals to make it more powerful but their arrangement is disrupted by alloying and it is more difficult for particles to slide over each other.

Q18. Why water is considered a polar molecule? 1/3

ANS: Water is a universal solvent; almost anything can be dissolved in water that’s why it is called a polar molecule. (Not well explained- rewrite)

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Q19. What are some of the differences between a compound and a mixture? 2/2

ANS: When two or more elements combine to form a new element, it is called a compound while mixture is an only mixing of two or more elements, they do not form any new element.

Q20. What is the formula for hydrogen sulfide, calcium sulfate, sodium sulfate, calcium oxide?

1/1

ANS: HYDROGEN SULFIDE: H2S CALCIUM SULFATE: CaSO4. SODIUM SULFATE: NaSO4 CALCIUM OXIDE: CaO

Q21. What is the collision theory? Explain 1/3

ANS: When particles of one reactant collide with particles of another reactant to form product is called collision theory. (Not explained- explain it)

Q22. How does a catalytic convertor in a car work? Explain 2/3

ANS: The catalyst used in car is platinum covered on a honeycomb structure. It works when the car expel the harmful gas, the structure automatically changes the harmful gas into two harmless gas, the catalyst help to speed up the reaction. (Good effort- re-write)

Q23. What is a catalyst? How does it work? 1/3

ANS : Catalyst only speeds up the reaction it but is not used up in the process . Catalysts work by mixing with any element to produce the product faster but it is not end up in the reaction. (not well explained- explain it)

Q24. What is activation energy? Explain. 1/3

ANS : When particles collide with each other at a minimum energy is called activation energy.(not explained- explain it)

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