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science > Unit 3: Chemical Composition > Flashcards

Unit 3: Chemical Composition Flashcards

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1
Q

Are all matter made of elements?

A

Yes

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2
Q

Are elements the building blocks
of all living and non-living things?

A

Yes

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3
Q

Can an element which is a substance, be split further into simpler substances by chemical means?

A

Yes

An element is a substance which cannot be split further into simpler substances by any chemical means.

An element is a pure substance which cannot be broken down into two or more simpler substances by chemical reactions.

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4
Q

Is an element the simplest form of matter?

A

Yes

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5
Q

Can elements exist as a single atom or molecule?

A

Yes
Elements can exist as a single atom or molecule.

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6
Q

Is an element only made up of one type of atoms?

A

Yes
An element is made up of only one type of atoms.

Atoms of each element are different from atoms of any other element.

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7
Q

What are Atoms?

A

Atoms are the smallest particles of an element that have the chemical properties of that element.

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8
Q

How many elements are there?

A

There are about 118 elements.

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9
Q

How many elements are found naturally on earth?

A

98 elements are found naturally on
Earth.

The rest are made artificially in the
laboratories!

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10
Q

What are metalloids?

A

Metalloids are elements that show some properties of both metals and non-metals.

Metalloids share properties of both metals and non-
metals.

Elements that are metalloids are B, Si, Ge, As, Sb, Te, Po

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11
Q

Characteristics of metals:

A

Shiny solids, except mercury
- a liquid at room temperature

Have high melting points and boiling points.

High density

Malleable ((of a metal or other material) able to be hammered or pressed into shape without breaking or cracking.)

Ductile ((of a metal) able to be drawn out into a thin wire.)

Good thermal conductivity and electrical conductivity

Sonorous (capable of producing produce a ringing sound when hit.)

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12
Q

Characteristics of non-metals:

A

Dull solids, liquids or gases

Have low melting points and boiling points

Low density

Brittle (Break easily into pieces)

Poor thermal conductivity and electrical conductivity

Non-sonorous (not capable of producing a ringing sound
when hit.)

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13
Q

Definition of malleable?

A

(of a metal or other material) able to be hammered or pressed into shape without breaking or cracking.

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14
Q

Definition of ductile?

A

(of a metal) able to be drawn out into a thin wire.

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15
Q

Definition of sonorous?

A

produce a ringing sound when hit.

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16
Q

Definition of brittle?

A

Break easily into pieces

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17
Q

Characteristics of Chemical Symbols?

A

1st letter is always capitalized
any other letter that follows the 1st letter is in lower case

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18
Q

What is a compound?

A

A compound is a substance which consists of two or more elements chemically combined together in a fixed composition.

Can be broken down into two or more simpler substances by chemical methods

Has different properties from its constituent elements

Elements in a compound are present in fixed proportion

Has a fixed melting and boiling point.

E.g.

water (hydrogen & oxygen)

sodium chloride (sodium & chlorine)

sugar (carbon, hydrogen & oxygen)

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19
Q

Are compounds formed by chemical reactions?

A

Yes
Compounds are formed by chemical reactions

Many elements combined directly to form compounds

Example: Burning of magnesium in oxygen to form
magnesium oxide (magnesium + oxygen)

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20
Q

Are the properties of compounds different from the properties of its constituent elements?

A

Yes
The properties of compounds are different from the properties of its constituent elements.

21
Q

Do compounds always have fixed compositions?

A

Yes
Compounds have fixed compositions.

E.g. Water always contains 11% hydrogen & 89%
oxygen by mass.

22
Q

How can compounds be broken down into simpler substances?

A

Compounds can only be broken down into simpler substances by chemical methods, such as decomposition.

Decomposition is usually carried out using
heat, electricity or even bacteria.

23
Q

How is a compound different from an element?

A

Compounds:
Made up of two or more types of atoms

Can be broken down into two or more simpler substances by chemical methods

Elements:
Made up of one type of atoms only

Cannot be broken down into any simpler substances

24
Q

How is a compound different from a mixture?

A

Compounds:
Made up of two or more types of atoms

Can be broken down into two or more simpler substances by chemical methods

Has different properties from its constituent elements

Elements in a compound are present in fixed proportion

Has a fixed melting and boiling point.

Mixture:
Made up of two or more substances not chemically combined together.

Can be separated into pure substances by physical method

Has similar properties as its constituent components

Components in a mixture are not present in fixed proportion

It melts/boils over a range of temperature.

25
Q

What is a mixture?

A

Consists of two or more substances which are not joined together chemically.

These substances may be elements or compounds.

Can be separated into pure substances by physical method

Has similar properties as its constituent components

Components in a mixture are not present in fixed proportion

It melts/boils over a range of temperature.

26
Q

Types of mixture:

A

Gas-Gas : Air

Gas-Liquid : Soft drinks (e.g. carbon dioxide in water)

Solid-Liquid : sea water (e.g. salt in water)
- solution (e.g. salt in water)
- suspension (e.g. sulfur in water)

Solid-Solid : Alloys (e.g. Brass - Mixture of copper and
zinc. Steel - Mixture of iron and carbon)

Solid-Gas : Smoke (e.g. solid particles suspended in air)

Liquid-Liquid : Vinegar (e.g. ethanoic acid in water)

27
Q

What is a solution?

A

Solution is a type of mixture in which one
substance dissolves completely in another
substance.

  • The substance that dissolves is called the solute.
  • The substance in which the solute dissolves is
    called the solvent. (Solvent is present in large amount.)

Most solvents are liquids, water is such a good solvent for many substances that it is called the universal solvent.

  • Examples: table salt solution, sugar solution,
    copper(II) sulfate solution
28
Q

What is the solute?

A

The substance that dissolves (in a solution) is called the solute.

29
Q

What is the solvent?

A

The substance in which the solute dissolves is
called the solvent. (Solvent is present in large amount.)

30
Q

Traits of a Solution:

A

It is homogeneous. (Its composition is uniform throughout)

The physical state is the same as that of the solvent.

The dissolved solute will not settle out or separate from the solvent.

The particles of the solute can no longer be seen. An
aqueous solution appears clear, light can pass through it fully.

(Note: aqueous solution is a solution where the solvent is water)

31
Q

What affects the rate of dissolving?

A
  • Temperature of solvent
  • Surface area of solute
  • Rate of stirring
32
Q

What is a homogeneous mixture?

A

A homogeneous mixture is a mixture that has uniform composition throughout.

A solution is a homogeneous mixture.

33
Q

What is a heterogeneous mixture?

A

A heterogeneous mixture is a mixture that has non-uniform composition throughout.

A suspension is a heterogeneous mixture. As the solid is unevenly distributed in the liquid, the
suspension has to be shaken or stirred to get a uniformity in it.

34
Q

What is solubility?

A

Solubility is the maximum mass of solute that can dissolve in a fixed volume of solvent at a fixed temperature.

The solution produced is a saturated solution.

35
Q

What is a saturated solution?

A

A saturated solution is a solution in which the maximum amount of solvent has been dissolved. Any more solute added will sit as crystals on the bottom of the container.

36
Q

What are the factors affecting solubility?

A
  • Nature (Type) of solute
  • Nature (Type) of solvent
  • Temperature of solvent
  • Pressure (applies to gas dissolving in liquid only)
37
Q

How do particles in a suspension behave?

A

Solid particles in a suspension do not dissolve, and can be seen in the suspension.

When a suspension is filtered, the solid particles are too large to pass through filter paper. Hence, they are left behind as a residue on the filter paper.

When a suspension is left to stand for some time,
the solid particles settle to the bottom.

Suspension is a heterogeneous mixture – the solid is unevenly distributed in a liquid.

Light will not pass through it fully.

38
Q

When left to stand, solid particles in a (solution / suspension) settle to the bottom.

A

suspension

39
Q

Light can pass through a (solution / suspension).

A

solution

40
Q

The components of a (solution / suspension) can be separated by filtration.

A

suspension

41
Q

What is a period in the periodic table?

A

A period in the periodic table is a horizontal row of chemical elements.

Elements in the same period have the same number of electron shells.

42
Q

What is a group in the periodic table?

A

A group in the periodic table is a vertical column of elements in the periodic table of the chemical elements.

Elements in the same group have similar chemical properties.

43
Q

What does the zigzag line separate?

A

The elements on the left side on the zigzag line are metals and those on the right side are non-metals.

The elements near the zigzag line are called metalloids. These elements have the properties of both metals and non-metals.

Zigzag line starts from Boron and ends at Astatine.

44
Q

Can a pure substance be an element or compoud?

A

Yes

45
Q

Can a mixture be a solution or suspension?

A

Yes

46
Q

what is the meaning of dilute?

A

it is when the liquid is weakened by the addition of water or another solvent

47
Q

what is the meaning of concentrated?

A

it means that a substance or solution is present in a high proportion relative to other substances; having had water or other diluting agent removed or reduced

48
Q

Are molecules compounds? (e.g. O2)

A

No
It is a molecule as it is made up of 2 atoms chemically combined together; but it is not a compound as it is made up of only 1 type of element chemically combined together.

A compound is a substance which consists of two or more elements chemically combined together in a fixed composition.

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