Chemistry Class 10: Elements and Atoms
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Questions and Answers

Why can't a scale model of the solar system be accurately made?

  • The interplanetary distances are too great. (correct)
  • There are too many planets to include.
  • The model would take up too much space.
  • The sizes of planets are too small.

    • Models of large objects, such as the solar system, are often made to scale.

    False (B)

    What is an example of a model that must be made to scale?

    Blueprints for a building.

    The sun would be about the size of a ______ in a model of the solar system on a football field.

    <p>dime</p> Signup and view all the answers

    Match the following descriptions with the correct term:

    <p>Model of interplanetary distances = Not to scale Blueprints = Made to scale Size representation of the sun = Dime Neptune in the model = 60 yards away</p> Signup and view all the answers

    What is the charge of a proton?

    <p>Positive (B)</p> Signup and view all the answers

    Neutrons have a positive charge.

    <p>False (B)</p> Signup and view all the answers

    What is the approximate mass of an electron in kg?

    <p>9.109 × 10^-31</p> Signup and view all the answers

    Protons have a mass approximately _____ times that of an electron.

    <p>1836</p> Signup and view all the answers

    Match the particles with their properties:

    <p>Electron = Negative charge Proton = Positive charge Neutron = No charge Atom = Basic unit of matter</p> Signup and view all the answers

    If an atom is neutral, how do the numbers of protons and electrons compare?

    <p>Protons and electrons are equal (B)</p> Signup and view all the answers

    Electrons are larger than protons and neutrons.

    <p>False (B)</p> Signup and view all the answers

    What do atomic models help scientists do?

    <p>Visualize the structure of atoms</p> Signup and view all the answers

    Who was the scientist that discovered the electron?

    <p>J.J. Thomson (B)</p> Signup and view all the answers

    Cathode rays bend toward a negative charge.

    <p>False (B)</p> Signup and view all the answers

    What is the charge of the particles that make up cathode rays?

    <p>negatively charged</p> Signup and view all the answers

    If electric current causes a cathode ray to bend toward a positive charge, the ray must be __________ charged.

    <p>negatively</p> Signup and view all the answers

    Match the following components of a cathode-ray tube with their functions:

    <p>Cathode = Source of electrons Anode = Receives electrons Electric Current = Causes particles to glow Cathode Ray = Stream of charged particles</p> Signup and view all the answers

    What did J.J. Thomson calculate from his experiments?

    <p>Charge-to-mass ratio of cathode ray particles (D)</p> Signup and view all the answers

    The charge-to-mass ratio of cathode ray particles changes with different gases.

    <p>False (B)</p> Signup and view all the answers

    What is a cathode ray?

    <p>A stream of charged particles</p> Signup and view all the answers

    What occurs when a negatively charged balloon is placed near a stream of water?

    <p>The water is attracted to the balloon. (A)</p> Signup and view all the answers

    Like charges attract each other.

    <p>False (B)</p> Signup and view all the answers

    What phenomenon is observed when you touch a metal object after walking on a carpet?

    <p>An electric shock.</p> Signup and view all the answers

    When two objects with opposite charges come together, they will ______.

    <p>attract</p> Signup and view all the answers

    What did scientists conclude about the properties of elements over time?

    <p>There is something other than mass affecting properties. (C)</p> Signup and view all the answers

    Match the following concepts to their descriptions:

    <p>Like charges = Repel each other Opposite charges = Attract each other Electric shock = Transfer of charge Atoms = Basic units of matter</p> Signup and view all the answers

    A charged balloon can build up a negative charge when rubbed with cloth.

    <p>True (A)</p> Signup and view all the answers

    Why does a balloon attract a stream of water?

    <p>Because of opposite charges.</p> Signup and view all the answers

    What was the main hypothesis of Rutherford regarding the plum pudding model?

    <p>Alpha particles would be repelled by the evenly spread positive charge. (C)</p> Signup and view all the answers

    In the gold foil experiment, most alpha particles were deflected at large angles.

    <p>False (B)</p> Signup and view all the answers

    What did the scattering of a few alpha particles at large angles indicate about atomic structure?

    <p>It indicated that atoms have a small, dense positively charged nucleus.</p> Signup and view all the answers

    During the gold foil experiment, ____ alpha particles were deflected backwards from the foil.

    <p>a few</p> Signup and view all the answers

    Match the following components of the gold foil experiment with their descriptions:

    <p>Alpha particles = Positively charged particles used in the experiment Gold foil = Thin sheet that alpha particles passed through Detection screen = Used to detect the scattering of alpha particles Deflection = Observed change in direction of alpha particles</p> Signup and view all the answers

    What was a surprising result observed by Rutherford during the gold foil experiment?

    <p>Some alpha particles were deflected back towards the source. (D)</p> Signup and view all the answers

    The gold foil experiment supported the plum pudding model of atomic structure.

    <p>False (B)</p> Signup and view all the answers

    What conclusion did Rutherford reach about atomic structure based on the results of his experiment?

    <p>Atoms have a small, dense nucleus with a positive charge.</p> Signup and view all the answers

    What property do metalloids possess that is useful in technology?

    <p>They conduct electric current. (B)</p> Signup and view all the answers

    Nonmetals are generally brittle at room temperature.

    <p>True (A)</p> Signup and view all the answers

    Name two examples of metalloids.

    <p>Boron, Silicon</p> Signup and view all the answers

    Metalloids have characteristics of both metals and __________.

    <p>nonmetals</p> Signup and view all the answers

    Match the following elements with their classifications:

    <p>Iron = Metal Oxygen = Nonmetal Silicon = Metalloid Copper = Metal</p> Signup and view all the answers

    What historical perspective did scientists hold about atoms in the mid-1800s?

    <p>Atoms are indivisible units differing only in mass. (D)</p> Signup and view all the answers

    Metalloids can only be found in gaseous state at room temperature.

    <p>False (B)</p> Signup and view all the answers

    What change regarding the understanding of atoms occurred over time?

    <p>Atoms were once thought to be indivisible but are now understood to be made up of smaller particles.</p> Signup and view all the answers

    Study Notes

    Comparing Elements Based on Properties

    • Matter can be classified into pure substances or mixtures
    • Metals shown in the figure are pure substances
    • Different metals react differently with acids
    • Metals are elements, or pure substances

    Classifying Elements

    • Elements are classified as metals, nonmetals, or metalloids
    • Metals are shiny, good conductors of electricity and heat, and generally bendable solids at room temperature
    • Nonmetals are poor conductors, often gases at room temperature, and can be brittle
    • Metalloids have characteristics of both metals and nonmetals, and are solids at room temperature. They are not as brittle as nonmetals, and conduct electricity less well than metals, but more than nonmetals. Used in computer chips (e.g., boron, silicon)

    Understanding Atoms

    • Scientific understanding of the atom has evolved over time
    • Early models of atoms depicted them as tiny indivisible spheres (differing only in mass)
    • Experiments showed that atoms aren't indivisible
    • Certain elements react with substances but others don't
    • Noble gases (e.g., helium, neon, argon) are barely reactive
    • Noble gases emit different colors of light when electric current passes through them

    Investigating Atomic Structure

    • Opposite charges attract, while like charges repel.
    • Experiments with cathode rays revealed the existence of electrons
    • Electrons have a negative charge and extremely small mass (much smaller than an atom)

    Identifying the Nucleus

    • Atoms have a nucleus (small, dense positively charged core), surrounded by a negatively charged electron cloud.
    • The gold foil experiment provided evidence for the atomic nucleus
    • Most alpha particles passed straight through the gold foil
    • A few alpha particles were deflected at large angles
    • The results contradicted the plum pudding model of the atom

    Describing Atomic Structure

    • Atoms are composed of subatomic particles: electrons, protons, and neutrons
    • Electrons have a negative charge and very small mass
    • Protons have a positive charge and a relatively large mass
    • Neutrons have no charge and a relatively large mass
    • Atoms are mostly empty space (containing the nucleus)

    Scale and Atomic Models

    • Atoms are too small to observe directly
    • Atomic models help visualize atomic structure
    • Models are often not drawn to scale because of the extreme differences in size and distances involved
    • Some models requiring scale (e.g., blueprints)

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    Related Documents

    Comparing Elements Based on Their Properties PDF

    Description

    This quiz covers the classification of matter into pure substances and mixtures, focusing on elements like metals, nonmetals, and metalloids. It also explores the evolution of atomic models, enhancing your understanding of atoms and their properties. Test your knowledge on these fundamental concepts in Chemistry!

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