1.  A compound of chlorine and potassium is sometimes used as a substitute for salt for people who have a restricted salt diet. The name of this compound is  
  (a) chlorine potassium.  
   (b) potassium chlorine.  
   (c) potassium chloride.   
   (d) potassium chlorate. 

2.  A heterogeneous mixture differs from a solution because 
  (a) a heterogeneous mixture is always solid.  
  (b) a heterogeneous mixture consists of elements.  
  (c) the different components can be seen in a heterogeneous mixture.   
  (d) a heterogeneous mixture consists of more substances than a solution.   

3.  The symbol Cl represents an atom with  
  (a) 17 protons, 20 electrons, 20 neutrons.  
  (b) 17 protons, 17 electrons, 17 neutrons.  
  (c) 20 protons, 20 electrons, 17 neutrons.   
  (d) 17 protons, 17 electrons, 20 neutrons.  

4.  The atomic radius of four elements in the first column of the periodic table are given below. 
  Li 152 pm  K 220 pm 
  Na 180 pm  Cs 260 pm 
  Use this information and the periodic table to decide which of the following is the best estimate for the atomic radius of Rb.  
  (a) 167 pm 
  (b) 200 pm 
  (c) 240 pm  
  (d) 275 pm 

5.  Which of the following gases is not a component of our atmosphere? 
  (a) hydrogen 
  (b) nitrogen 
  (c) carbon dioxide 
  (d) argon  

6.  Scientists have been able to identify about 110 elements and a few million compounds. How many different kinds of atoms are there? 
  (a) About 110.  
  (b) A few million. 
  (c) Two. 
  (d) It's impossible to tell from the information given. 

7.  The atomic model has been modified many times over the years. This happened because 
  (a) scientists have become smarter with time.  
  (b) new evidence became available to scientists.  
  (c) the actual nature of the atom has changed with time.  
  (d) more elements were discovered.  

8.  An atom can form a negative ion by 
  (a) losing electrons  
  (b) gaining electrons   
  (c) losing protons  
  (d) gaining protons 

9.  An example of a physical change is 
  (a) toasting a piece of bread 
  (b) the explosion of dynamite 
  (c) boiling oil  
  (d) the rusting of iron 

10.  One of the physical properties of matter that you read about is viscosity. This term is usually used to describe oils used in automobile engines. If oil A is more viscous than oil B, then this means that: 
  (a) oil A is thinner than oil B  
  (b) oil A is thicker than oil B   
  (c) oil A is a more expensive oil than oil B  
  (d) oil A is more soluble in water than oil B 

11.  Rows in the periodic table are also referred to as 
  (a) periods. 
  (b) families. 
  (c) groups. 
  (d) columns. 

12.  In which group of the periodic table are the alkali metals found?  
  (a) 1   
  (b) 2  
  (c) 17  
  (d) 18 

13.  Which scientist first proposed the existence of the nucleus in atoms? 
  (a) Rutherford   
  (b) Bohr  
  (c) Thomson  
  (d) Dalton 

14.  You are given blocks of four different materials of identical mass. The materials are foam, gold, aluminum, and ice. Which block would have the largest volume? 
 (a) foam  
 (b) gold  
 (c) aluminum 
 (d) ice 

15.  In the periodic table, elements with similar chemical properties are found in 
  (a) vertical columns.  
  (b) horizontal rows.  
  (c) periods.  
  (d) diagonal rows. 

16.  The fire triangle is a useful way of remembering the components of a combustion reaction. The three parts of the triangle are 
  (a) heat, fuel, oxygen   
  (b) heat, fuel, hydrogen  
  (c) light, fuel, oxygen  
  (d) reactants, products, fossil fuels 

17.  A student finds a sample of a clear, colourless, odourless liquid in the science laboratory. With his teacher's permission, he decides to measure the boiling point of the liquid, and finds it to be 106 degrees C. Based on that observation, what is a reasonable conclusion for the student to reach? 
  (a) The liquid is probably water.  
  (b) The thermometer was faulty.  
  (c) The liquid is not pure water.   
  (d) He heated the liquid too quickly. 

18.  Which of the following is the correct arrangement of electrons in a sulphur atom, atomic number 16? 
  (a) 2, 8, 4, 2 
  (b) 2, 8, 6  
  (c) 6, 8, 2 
  (d) 2, 6, 8 

19.  Which of the following materials, based on appearance, is not a solution?  
  (a) Perfume  
  (b) Vinegar  
  (c) Spaghetti sauce   
  (d) Apple juice 

20.  Identify the chemical change in the following list: 
  (a) the crushing of stones 
  (b) the formation of clouds 
  (c) the separation of cream from milk  
  (d) the burning of a candle  

21.  Which one of the following is an example of a chemical change? 
  (a) the melting of candle wax 
  (b) making sawdust by sawing wood 
  (c) the rotting of food  
  (d) the breaking of glass 

22.  Isotopes of the same element have  
  (a) the same number of protons and a different number of neutrons.   
  (b) the same number of neutrons and a different number of protons.  
  (c) the same number of protons and a different number of electrons.  
  (d) the same number of electrons and a different number of protons. 

23.  The density of aluminum is 2.7 g/cm3. Four students each measured the mass and volume of a sample of metal; their results are shown below. Only one of the students actually had a sample of aluminum; the other students had different materials. From the information given, decide which student had the aluminum. 
  (a) mass = 28.4 g volume = 76.7 cm3
  (b) mass = 37.4 g volume = 15.1 cm3
  (c) mass = 88.3 g volume = 30.2 cm3
  (d) mass = 76.7 g volume = 28.4 cm3

24.  If the atomic number of an atom is represented by X and the mass number is represented by Y, the number of neutrons in an atom of the element is  
  (a) Y-X 
  (b) X-Y 
  (c) X+Y 
  (d) Y 

25.  Dalton's atomic theory was one of the most important theories in chemistry. In this theory, atoms were considered to be 
  (a) tiny indivisible spheres.  
  (b) the same for all elements.  
  (c) made up of smaller particles.  
  (d) positively charged. 

26.  Chemists believe that the chemical properties of an element are directly related to the  
  (a) number of neutrons in the nucleus of an atom.  
  (b) atomic mass of the atom.  
  (c) electrons in the outermost orbit of the atom.  
  (d) the mass number of the atom. 

27.  Bohr proposed that the line spectrum of an element is caused by 
  (a) electrons moving from a higher energy level to a lower energy level.   
  (b) electrons moving from a lower energy level to a higher energy level.  
  (c) electrons leaving the atom.  
  (d) protons moving from the nucleus to one of the energy levels. 

28.  The particle theory of matter is a useful scientific model because 
  (a) it proves that matter is made of particles. 
  (b) it allows scientists to explain many of the properties of matter.  
  (c) it is easy to understand. 
  (d) it was developed by famous scientists. 

29.  When a hydrocarbon such as coal, natural gas, or oil burns, the products are most likely to be 
  (a) carbon and oxygen 
  (b) hydrogen and water 
  (c) hydrogen and carbon 
  (d) carbon dioxide and water 

30.  When compounds containing certain metals are placed in a flame, different flame colours are produced. For example, sodium compounds always produce yellow flames. The reason that this happens is because 
  (a) all atoms of the metal have the same mass. 
  (b) all atoms of the metal have the same symbol. 
  (c) all atoms of the metal have the same number of neutrons. 
  (d) all atoms of the metal have the same electron arrangement.  

31.  The particles that make up most of the mass of an atom are 
  (a) the protons and electrons.  
  (b) the neutrons and electrons.  
  (c) the protons and neutrons.   
  (d) only the neutrons. 

32.  Which of the following statements is not part of Dalton's atomic theory? 
  (a) All substances are composed of small, indivisible particles called atoms.  
  (b) The atoms of a given element are identical in every respect. 
  (c) The three main particles in atoms are protons, neutrons, and electrons.  
  (d) In chemical reactions, atoms combine in simple, whole-number ratios. 

33.  Mendeleev is sometimes referred to as "the father of the periodic table." He knew some of the properties of about 64 elements, and by arranging the elements in a certain way, he formed a table in which elements with similar properties appeared in the same column. To produce this table, Mendeleev arranged the known elements in order of 
  (a) increasing atomic number.  
  (b) increasing atomic size.  
  (c) increasing atomic mass.  
  (d) the dates of discovery of the elements. 

34.  Which of the following is a chemical property of sulphur?  
  (a) It is bright yellow in colour. 
  (b) It is a solid at room temperature. 
  (c) It is brittle. 
  (d) It is combustible.   

35.  In a famous experiment carried out in 1911, Ernest Rutherford bombarded a thin sheet of gold with high-speed, positively charged particles. Based on the behaviour of these particles, Rutherford proposed that atoms possessed 
  (a) a very small, positively charged, dense region in the centre of the atom.   
  (b) a very small, negatively charged, dense region in the centre of the atom.  
  (c) very small, positively charged particles that moved at high speed.  
  (d) equal numbers of positive and negative particles. 

36.  A student measured the mass and volume of three samples of material; his results are shown below. 
  Block              Mass (g)                     Volume (cm3) 
  A                    30.8                             27.5 
  B                    35.2                             27.5 
  C                    30.8                             24.0 
  Which samples could be made of the same substance? 
  (a) A and B 
  (b) A and C 
  (c) B and C  
  (d) A, B, and C 

37.  Imagine that you are on vacation in Spain. While out for a walk, you find a container that is still full of a solid material. You do not speak or read the language, so you can't tell what the container contains. A symbol like the one shown is printed on the label of the container. What do you conclude about the solid in the container? 

   (a) It is explosive.  
   (b) It is poisonous. 
   (c) It is corrosive.  
   (d) It is flammable. 

38.  All of the following terms are associated with the atom. Which one has the smallest mass?  
  (a) electron  
  (b) proton 
  (c) neutron  
  (d) nucleus  

39.  Electrons are 
  (a) positively charged particles found outside the nucleus in an atom.  
  (b) negatively charged particles found outside the nucleus in an atom.  
  (c) neutral particles found in the nucleus in an atom. 
  (d) negatively charged particles found in the nucleus in an atom. 

40.  The element with atomic number 11 is most likely to have similar chemical properties to the element with atomic number  
  (a) 2  
  (b) 10  
  (c) 12  
  (d) 19  

41.  The total number of atoms represented by the formula K2Cr2O7 is 
  (a) 1 
 (b) 3 
 (c) 11  
 (d) 28 

42.  Several models of the atom have been suggested by scientists since the beginning of the nineteenth century. What is the correct chronological order (earliest to latest) of the models proposed by the scientists listed below? 
  (a) Dalton, Bohr, Thomson, Rutherford  
  (b) Dalton, Thomson, Rutherford, Bohr   
  (c) Thomson, Dalton, Rutherford, Bohr  
  (d) Dalton, Rutherford, Thomson, Bohr 

43.  An atom with an atomic number of 38 and a mass number of 88 contains  
  (a) 50 neutrons   
  (b) 50 electrons  
  (c) 38 neutrons  
  (d) 88 protons 

44.  How many groups of elements are there in the modern periodic table? 
 (a) 3  
 (b) 18   
 (c) 7  
 (d) 14 

45.  Elements that possess some properties of metals and some properties of nonmetals are called  
  (a) alkali metals. 
  (b) metalloids. 
  (c) noble gases. 
  (d) heavy metals. 

46.  When baking soda is heated, it produces carbon dioxide. If you were to sprinkle baking soda on a small fire in your kitchen, what do you predict would happen? 
  (a) The fire will burn brighter.  
  (b) There will be an explosion.  
  (c) There will be no change in the fire.  
  (d) The fire will burn less intensely and may go out.  

47.  Read the following four statements about a solid substance. 
  I The solid forms cube-shaped crystals 
  II The density of the solid is 2.4 g/cm3
  III The mass of the solid is 77.5 g 
  IV The melting point of the solid is 689 degrees C 
  Which of these properties would be more useful in identifying the solid? 
  (a) I and III 
  (b) II and III 
  (c) II and IV  
  (d) III only  

48.  Two elements X and Y (not their symbols) are members of the same family of elements. It can therefore be concluded that the elements have the same 
  (a) atomic radius. 
  (b) atomic mass. 
  (c) number of outer-level electrons. 
  (d) physical state at room temperature. 

49.  Only one of the following statements is correct. Identify that statement. 
  (a) All compounds are pure substances.   
  (b) All mixtures are heterogeneous.  
  (c) All pure substances are elements.  
  (d) All solutions consist of a solid dissolved in a liquid. 

50.  Protons are 
  (a) positively charged particles found outside the nucleus in an atom. 
  (b) negatively charged particles found outside the nucleus in an atom. 
  (c) neutral particles found in the nucleus in an atom. 
  (d) positively charged particles found in the nucleus in an atom.  

51.  The number of electrons in the outermost orbit of a phosphorus atom is 
  (a) 2  
  (b) 8  
  (c) 5   
  (d) 15 

52.  In Bohr's planetary model of the atom, he suggested that 
  (a) electrons could be found only in certain orbits or energy levels.   
  (b) the closer an electron is to the nucleus, the higher its energy.  
  (c) electrons always stay in the same energy level.  
  (d) the orbit closest to the nucleus can hold eight electrons. 

53.  The numbers of protons, electrons, and neutrons in an atom of 144Cs are  
  (a) 55 protons, 55 electrons, 144 neutrons. 
  (b) 55 protons, 55 electrons, 89 neutrons.  
  (c) 89 protons, 89 electrons, 144 neutrons. 
  (d) 55 protons, 89 electrons, 89 neutrons.  

54.  Which of the following elements would you expect to react in a manner most similar to nitrogen? 
  (a) phosphorus (P)   
  (b) sodium (Na)  
  (c) neon (Ne)  
  (d) oxygen (O) 

55.  Which one of the following statements about the particles in a piece of silver is incorrect? 
  (a) All of the particles have the same mass. 
  (b) The particles are always moving. 
  (c) There are strong forces of attraction between the particles. 
  (d) As the temperature increases, the particles move more slowly. 

56.  All of the following statements are part of the particle theory of matter except one. Identify the exception. 
  (a) Different substances are made of different particles. 
  (b) The particles in solids are harder than the particles in liquids.  
  (c) The particles are always moving. 
  (d) There are forces of attraction between the particles.  

57.  Which of the following is a chemical property of carbon? 
  (a) It is a black solid. 
  (b) In the form of graphite, it conducts electricity. 
  (c) It is insoluble in water. 
  (d) It burns readily. 

58.  Cesium is a member of the alkali metal group. The formulas of cesium chloride and cesium oxide are 
  (a) CsCl and CsO.  
  (b) CsCl and Cs2O.   
  (c) CsCl2and CsO.  
  (d) CsCl and CsO2.  

59.  The "raisin bun" model of the atom was proposed by  
  (a) Dalton 
  (b) Thomson  
  (c) Rutherford 
  (d) Bohr 

60.  The melting points of some of the group one elements are shown below. 
  Li 181 degrees C  K 63 degrees C 
  Na 98 degrees C   Rb 39 degrees C 
  Use this information and your knowledge of periodic trends to select the best estimate for the melting point of Cs (cesium).  
  (a) 220 degrees C 
  (b) 120 degrees C  
  (c) 45 degrees C 
  (d) 25 degrees C  

61.  Only one of the following lists does not consist entirely of symbols for elements. Which one? 
   (a) C, He, Mg, Cu 
  (b) H, ASA, P, Fe  
  (c) He, N, Cl, O 
  (d) Ca, Ne, Fe, He 

62.  Only one of the following statements is correct. Identify that statement. 
  (a) All compounds consist of two or more elements.   
  (b) All pure substances are elements.  
  (c) All mixtures are solutions.  
  (d) All solutions are heterogeneous. 

63.  The most metallic elements in the periodic table are found:
  (a) on the extreme right of the table  
  (b) on the extreme left of the table   
  (c) in the middle of the table  
  (d) in the second column 

64.  What determines the order of elements in the modern periodic table? 
  (a) atomic size  
  (b) atomic mass  
  (c) number of neutrons  
  (d) number of protons  

65.  In the following list, there is only one element. Which is the element?  
  (a) Brass  
  (b) Sugar  
  (c) Air  
  (d) Fluorine  

66.  Carbon dioxide and carbon monoxide are compounds made up of the elements carbon and oxygen. Based on that information only, which of the following statements is most likely correct? 
  (a) The two compounds have different properties.  
  (b) Carbon dioxide is a gas and carbon dioxide is a liquid.  
  (c) The two compounds have the same properties.  
  (d) One compound is more poisonous than the other. 

67.  All of the following are properties of magnesium. Identify the physical property. 
  (a) Magnesium burns in air with a brilliant white flame. 
  (b) Magnesium reacts with hydrochloric acid to produce a gas. 
  (c) Magnesium is a good conductor of electricity. 
  (d) Magnesium combines with nitrogen to form a black powder. 

68.  In Rutherford's famous experiment, where he bombarded gold foil with very fast-moving, positively charged alpha particles, what surprising observation did Rutherford make?  
  (a) All of the alpha particles went straight through the foil.   
  (b) Most of the alpha particles bounced back from the foil.  
  (c) A few alpha particles bounced back from the foil.   
  (d) None of the alpha particles went straight through the foil. 

69.  The most reactive elements in the periodic table are found in  
  (a) groups 1 and 18. 
  (b) groups 2 and 15. 
  (c) groups 3 and 4. 
  (d) groups 1 and 17. 

70.  Which one of the following substances is an element?  
  (a) Water  
  (b) Salt  
  (c) Helium   
  (d) Milk  

71.  Complete the blanks in the following table. 
  atomic             mass               number of          number of          number of  
  number            number             protons             electrons            neutrons  
  9                        19                       ?                        ?                          ?  
  ?                         ?                       20                       ?                        21  
  ?                       56                        ?                       26                         ?  
  35                       ?                        ?                         ?                       45 

72.  Write a sentence describing the major difference between the way the elements are arranged in the modern periodic table and the way they were arranged in Mendeleev's periodic table. 

73.  Label each of the following properties as physical or chemical. 
  (a) Copper sulphate crystals are blue.  
  (b) Gold is an excellent conductor of electricity.  
  (c) Iron rusts when exposed to air and water.  
  (d) Salt is soluble in water.  
  (e) Calcium reacts with water to produce hydrogen.  
  (f) Gasoline burns in an automobile engine. 

74.  Fill in the blanks in the following sentences with a word or phrase to make the sentence correct. 
  (a) Solubility describes the ability of a substance to __________________ in a solvent.  
  (b) If a substance burns when exposed to a flame, it is said to be ___________________.  
  (c) Copper does not change when it conducts electricity; this means that the ability to conduct electricity is a ___________________ property of copper.   
  (d) The temperature at which a solid changes to a liquid is called the ___________________.  
  (e) An alloy is a mixture of _______________. 

75.  (a) Describe one way in which solutions and heterogeneous mixtures are alike. 
  (b) Describe one way in which solutions and heterogeneous mixtures are different. Write your answer in full sentences. 

76.  Chlorine is used in water purification systems and in some swimming pools to remove bacteria from the water. Chlorine gas irritates lungs and is toxic and lethal at high concentrations. What symbol would you expect to see on a container of chlorine gas? 
 
77.  Write a short paragraph describing what is common about the electron arrangement of 
  (a) the alkali metals.  
  (b) the halogens.  

78.  Write a sentence describing how the elements in a group in the modern periodic table are related. 

79.  Write down the number of protons, neutrons, and electrons in each of the following atoms. 
  (a) 22Ne  
  (b) 40Ar  
  (c) 64Cu 

80.  If you break a test tube or beaker during an experiment, how should you dispose of the broken glass? Explain why this is done.

81. The following diagrams represent the atomic models proposed by Dalton, Thomson, Rutherford, and Bohr. Write the correct names beside each diagram.   

82.  Explain why it is extremely unlikely that a new element will be discovered that fits between sodium and magnesium on the periodic table. Write your answer in complete sentences.  

83.  Sodium carbonate and potassium carbonate are both white powders that dissolve readily in water. When hydrochloric acid is added to samples of both compounds, carbon dioxide is given off. The properties just described do not allow you to distinguish between the two compounds. Suppose that you are given a sample of a white powder known to be either sodium carbonate or potassium carbonate. Design an experiment that would allow you to identify the compound in your sample. Describe the procedure you would follow, along with the observations that would allow you to identify the compound. 

84.  The formula for sodium carbonate is Na2CO3. List the names and formulas for the carbonates of the other elements in group 1. 

85.  Match the following scientists with their contributions to our knowledge of the structure of the atom (statements (a) to (d)).  
  Scientists: Bohr, Rutherford, Dalton, Thomson  
  (a) Electrons in atoms revolve around the nucleus much like the planets revolve around the sun.  
  (b) All elements are made up of atoms, which are like tiny indivisible spheres; different elements have different atoms.  
  (c) The atom is like a raisin bun, with the raisins representing the electrons, and the dough of the bun the rest of the atom.  
  (d) At the centre of the atom is a very small, extremely dense, positively charged region called the nucleus. 

86.  Write symbols for the following elements that are found in living things. 

  oxygen, carbon, hydrogen, nitrogen, phosphorus, sulphur, chlorine, sodium, potassium, magnesium, iodine, calcium, and ion. 

87.  Mark each of the following statements true or false. If the statement is false, rewrite it to make it correct. 
  (a) An atom of the isotope 60Fe has 26 neutrons in its nucleus.  
  (b) An atom of 48Ti contains 22 protons, 22 electrons, and 26 neutrons.  
  (c) Isotopes of an element contain the same number of electrons.  
  (d) The proton and the neutron have almost the same charge.  
  (e) 26Mg has two more neutrons than 24Mg. 

88.  Decide if each of the following statements is true or false. If the statement is false, rewrite it to make it correct. 
  (a) Democritus, around 400 B.C., was the first person to use the word "atom" to refer to tiny particles of matter.  
  (b) Dalton stated that atoms could be broken apart into smaller particles.  
  (c) Rutherford proposed that all atoms had a tiny, negatively charged core called a nucleus.  
  (d) According to Thomson's model of the atom, tiny particles called protons were embedded in a negatively charged sphere.  
  (e) Rutherford stated that most of the mass of an atom was found in its nucleus. 

89.  Many changes take place in an automobile. State whether each of the following changes is physical or chemical, and explain why you made the choice that you did. 
  (a) Your windshield has frost on it after a cold night. 
  (b) In the fuel injector (or carburetor on older cars), the gasoline is vapourized and mixed with air before it is sprayed into the cylinders of the engine. 
  (c) In the cylinders, a spark ignites the mixture of gasoline and air, causing an explosion and forming gases that go through the exhaust system. 
  (d) As the car heats up, the frost on your windshield disappears. 
  (e) The exhaust gases pass through the catalytic converter, where some of the gases are converted into different gases. The catalytic converter, which is quite far from the engine, also gets very hot. 
  (f) For the first few minutes, the water vapour in the exhaust gases condenses as it hits the cold air and forms a white cloud. 
  (g) After some years of use, a few holes appear in the exhaust system due to rust. 

90.  State whether each of the following changes is a physical change or a chemical change. Give a reason for your answer in each case. 
  (a) The snow on the sidewalk outside your house melts. 
  (b) A piece of silverware gradually tarnishes when left exposed to air. 
  (c) Milk turns sour after several days. 
  (d) The three sugar cubes that you add to your coffee disappear when you stir the coffee. 
  (e) You accidentally spill some bleach on your favourite blue shirt and end up with white stains on the shirt.  
  (f) To reconnect a loose wire in your computer, the technician melts some solder. 

91.  Most aerosol cans list a warning such as this. Do not store near heat, or throw in a fire when done. Container may explode. Which symbol would you find on an aerosol can? 

92.  Classify each of the following changes as physical or chemical. 
  (a) The melting of ice cream 
  (b) The formation of frost 
  (c) The fermenting of grapes into wine 
  (d) The mixing of cake batter in a bowl 
  (e) The explosion of a firecracker 
  (f) The baking of bread in the oven 

93.  (a) In the original periodic table proposed by Mendeleev, the elements were arranged in order of a certain property. State that property. 

  (b) In the modern periodic table, the elements are arranged in order of another property. State that property.  
  (c) Write a sentence or two explaining how Mendeleev was able to come up with a periodic table that is close to the modern periodic table when he used the "wrong" property to arrange the elements. [Hint: Are the two properties related in any way?] 
 
94.  Answer the following questions about Mendeleev and his first periodic table. 
  (a) Write a sentence describing what was true about elements that Mendeleev placed in the same vertical column in his periodic table.  
  (b) The elements in Mendeleev's table appeared in a particular order. Write a short paragraph describing that order. 
  (c) Write a paragraph explaining how Mendeleev knew when to start a new row.  

95.  In Mendeleev's original periodic table, he left some gaps. Write a short paragraph explaining why this was done. 

96.  List five items found in your science class that are considered to be safety items. Give the purpose of each item.

97.  Read each of the following sentences. Decide if the sentence is true or false. If the sentence is false, rewrite it to make it correct. 
  (a) Physical changes result in the formation of new substances. 
  (b) A chemical property of salt is that it forms white crystals in the shape of a cube. 
  (c) The formation of dew is a physical change. 
  (d) Non-metals are usually malleable and ductile. 
  (e) The starting substances in a reaction are called the products. 
  (f) To determine the density of a sample of material, you must measure the mass and volume of the sample. 

98.  Write a short paragraph explaining why your teacher asks students with long hair to tie their hair back when carrying out an experiment. 

99.  Write a sentence describing the major difference between the way the elements are arranged in the modern periodic table and the way they were arranged in Mendeleev's periodic table. 

100.  Write a short paragraph describing what is common about the electron arrangement of 
  (a) the alkali metals.  
  (b) the halogens.  

101.  When hydrogen peroxide, a clear, colourless liquid, comes in contact with blood, it fizzes, showing that a gas is produced. Suppose that you have collected three test tubes of this gas. Write a short report describing the tests that you would carry out to identify the gas. Include the observations that would be made during the tests that allow you to say what the gas is or is not.  

102.  An article appears in your local newspaper announcing the discovery of a new element. In one part of the report, it states that scientists were able to isolate two isotopes of the element, 293X and 295X. Because you have just studied isotopes in your grade 9 science class, you know that this is incorrect. Write a letter to the editor of the newspaper explaining the error. 

103.  The densities of four different types of wood are shown in the table below. 

  Wood                     Density (g/cm3) 
  Ironwood                      1.24 
  Birch                             0.66 
  Red cedar                      0.37 
  Balsa                             0.12 
  (a) Which of the woods listed would sink in water? Write a short paragraph explaining your answer. 
  (b) If you were building a model airplane, which type of wood would be your best choice? Explain your answer. 
  (c) Suppose that you are given a block of wood that measures 9 cm x 6 cm x 5 cm, and has a mass of 179 g. Use this information to determine the identity of the wood. 

104.  Chlorine consists of two isotopes: chlorine-35 and chlorine -37.
  (a) Describe what is similar about these two isotopes.  
  (b) Describe what is different about the two isotopes. Write your answers in complete sentences. 

105.  For every atom except one, the mass number is greater than the atomic number. The exception is the 1H atom. Write a paragraph explaining in terms of the particles in atoms why this is the case.  

106.  Coal, oil, and natural gas are often referred to as "fossil fuels." 
 (a) Write a sentence explaining why this term is used. 
  (b) Name the two elements that are mainly present in these fuels. 
  (c) Write a paragraph explaining why fossil fuels are so important to our society. 
  (d) Identify the major products formed when fossil fuels burn. 
  (e) Name some of the other substances that can be produced when fossil fuels burn. 
  (f) Write a sentence or two outlining some of the problems associated with the products of the burning of hydrocarbons.

107.  One of the most famous recent uses of carbon-14 dating was to establish the authenticity of the Shroud of Turin. Use print and electronic resources to research this topic. Write a short report stating your findings and outlining what the Shroud of Turin is and what carbon-14 dating found about its age. 

108.  You find a piece of metal in an old chest in your attic. It looks like gold, but it could be a cheap metal made to look like gold. You remember from your science class that gold has a high density of close to 20 g/cm3, and that gold is much denser than most other metals. You decide to carry out an experiment to measure the density of the piece of metal that you found; the mass of the metal is found to be 687 g and its volume is 54 cm3. Based on these measurements, is it likely that the metal you found is gold? Write a paragraph explaining how you arrive at your answer. 

109.  A bar of soap measures 10 cm x 5 cm x 3 cm and has a mass of 120 g. 
  (a) Calculate the density of the soap. 
  (b) Write a short paragraph explaining whether the soap will sink or float in water. 

110.  Write a paragraph explaining why it was necessary to reject or change the models of the atom proposed by Dalton, Thomson, and Rutherford. 

111.  (a) Under certain conditions, an electron in an atom can move from a lower energy level to a higher energy level. Write a sentence explaining what has to be done to make this happen.  
  (b) Later, the electron in a higher energy level will return to a lower level. When this happens, describe what is given out by the atom. Write your answer in paragraph form.

112.  Ozone is a form of oxygen that performs a vital function in the upper atmosphere. It is able to filter some of the harmful ultraviolet rays from the sun. Several years ago, scientists noticed that the ozone layer was becoming thinner in places; it was suggested thatthere were holes in the ozone layer. Use your local library or the Internet to find out what substances caused the holes in the ozone layer, what these substances were used for, and what was done to solve this problem. Write a short report describing your findings. 

113.  Advertising signs that contain neon gas in clear glass tubes always produce a red glow. The glow appears when electricity is passed through the tube. Use Bohr's theory to explain this observation. 

114.  Lubricating oil can be purchased in different viscosities. Suppose that you have two bottles of oil, one of high viscosity and the other of low viscosity. There is exactly the same volume of oil in each bottle, but the labels have fallen off both bottles and you have to know which is which. All that you have available is some empty containers. Design an experiment that would enable you to know which oil is more viscous.

115.  Sulphur dioxide and sulphur trioxide are two different compounds consisting only of sulphur and oxygen. A molecule of each substance contains one sulphur atom, but a different number of oxygen atoms. (You should be able to guess how many oxygen atoms are present in each molecule.) Draw a diagram showing the two different molecules.   

116.  Models for molecules can be the ball-and-stick models that you built in class or they can be drawings on paper. Each type of model is useful. 
    The combining capacities for some elements are given below.  
  hydrogen 1  
  oxygen 2  
  carbon  4  
  nitrogen 3  
  chlorine 1  
    Use this information to draw structural diagrams for the following molecules. You may find a double or triple bond in some of these molecules  
    (a) chloroform, CHCl3, a compound that used to be used as an anesthetic  
  (b) oxygen dichloride , OCl2 
  (c) ethane, C2H6 
  (d) hydrogen cyanide, HCN  
  (e) formic acid, HCOOH, a compound found in stinging nettles 

117.  Carry out the following experiment at home with your parents' permission. List your observations after each step. 
  (a) Place a few corn kernels or two mothballs in a tall glass three-quarters full of water.   
  (b) Add about 10 mL of vinegar to the container and mix with a spoon.  
  (c) Add about 10 mL of baking soda to the container.  
  Explain the movement of the corn kernels or mothballs by using what you have learned about density.