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science > Unit 2: Physical Properties > Flashcards

Unit 2: Physical Properties Flashcards

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1
Q

What is density?

A

The density of a substance is defined as its mass per unit volume.

Symbol: ρ

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2
Q

What is the formula for density?

A

Density = Mass / Volume

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3
Q

What is the SI Unit for Density?

A

kg/m³ or kg m^-3

but normally its g/cm³ or g cm^-3 (not si unit tho)

1000 kg/m³ = 1 g/cm³

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4
Q

What happens when an object is placed in a liquid of lower density than itself?

A

the object sinks because the object’s density is higher than the liquid

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5
Q

What happens when an object is placed in a liquid of a greater density than itself?

A

the object floats because the object’s density is lower than the liquid

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6
Q

What are the 3 materials that always float in water no matter what size or shape they are?

A

Wood, Cork and Ice

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7
Q

What materials may float or sink depending on their shape?

A

Modelling Clay and Steel

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8
Q

Can density help to identify a substance?

A

Yes

All substances have a unique density

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9
Q

Is Density a physical property?

A

Yes

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10
Q

Is Density constant at a given temperature?

A

Yes

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11
Q

Do all pieces of the same substance have the same density regardless of their volume or mass?

A

Yes

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12
Q

What happens when an object has the same density as the liquid it is in?

A

When an object has the same density as a liquid, it will suspend (remain in the middle of the liquid; neither float nor sink)

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13
Q

What is the formula for mass?

A

mass = density x volume

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14
Q

What is the formula for volume?

A

volume = mass / density

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15
Q

Ceramic

A
  • Made from clay
  • Poor conductor of electricity
  • Hard
  • Can be moulded into shapes
  • Does not corrode
  • Has a high melting point
  • Fragile
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16
Q

Metal

A
  • Shiny
  • Good conductor of electricity
  • Good conductor of heat
  • Can be moulded into shapes
  • Can be bent without breaking
17
Q

Glass

A
  • Transparent
  • Poor conductor of electricity
  • Poor conductor of heat
  • Can be moulded into shapes
  • Has a high melting point
  • Fragile
18
Q

Fibres

A
  • Can be spun into threads and woven into fabrics
  • Able to absorb dyes
  • Poor conductors of electricity
  • Poor conductors of heat
19
Q

Plastic

A
  • Lightweight
  • Does not corrode
  • Can be moulded into shapes
  • Has a low melting point
  • Poor conductor of electricity
  • Poor conductor of heat
20
Q

Strength

A

• Ability to support a heavy load without changing its shape permanently

21
Q

Hardness

A
  • Its resistance to wear and tear, and scratches
  • Ability to scratch another material
  • A hard material can scratch another material that is softer than itself
22
Q

Flexibility

A

• Ability to bend without breaking and return to its original shape

23
Q

Electrical conductivity

A

• Measure of how easily an electric current passes through it

24
Q

Thermal conductivity

A

• Measure of how easily heat passes through it

25
Q

Melting point / Boiling point

A

• Temperature at which the material changes state from a solid to a liquid/ liquid to gas

26
Q

How do we measure mass?

A

• Mass is the amount of matter in an object. The S.I. unit is the kilogram (kg). Other common units are the gram (g), milligram (mg) and tonne (t).
• We use the electronic balance to measure mass.
• The precision of the electronic balance is 0.0 g. (1 decimal places)
Note that some electronic balance can also record up to 0.00 g (2 decimal places).

27
Q

How do we measure volume?

A
  • Volume is the amount of space an object occupies. The S.I. unit is the cubic metre (m³).
  • Other common units include cubic centimetres (cm³) and millilitres (ml).
  • When measuring the amount of liquid in a measuring cylinder, position the eye so that the line of sight is levelled with the bottom of the meniscus (curved surface of the liquid).
  • The displacement method can be used to measure the volume of irregular objects. (put water into measuring cylinder. Record initial water level, then put in the object, then record the final water level, then take final – initial = volume of object). This works as long as the object does not float on water and can fit in the measuring cylinder.
28
Q

How do we measure length?

A
  • Length is the distance between 2 points. The S.I. unit is the metre (m). Other common units are the kilometre (km), centimetre (cm) and millimetre (mm).
  • We can use the measuring tape to measure curved lengths or long surfaces and metre ruler / digital vernier calipers for short lengths and diameters of small objects.
29
Q

How to measure the volume of irregular solids?

A

Method 1:
The volume of water (A) is taken in a measuring cylinder. The object is then lowered completely into the measuring cylinder. Because objects have mass and takes up space, when the object is lowered into the measuring cylinder, it will cause the water level to rise (B), The volume of the object can be found by subtracting the volume of water from the total volume of the object and the water (B - A).

Method 2:
Method 1 cannot be used if the irregular solid is bigger than the diameter of the measuring cylinder. Hence the volume of such solids can be measured using the displacement can or Eureka can. The can is placed on a stand with a measuring cylinder beneath its spout. Water is poured into the can until it overflows into the cylinder. The cylinder with water is replaced with a clean and dry measuring cylinder. The irregular object is then slowly lowered into the can till it is completely immersed in the water. The volume of the solid is the volume of water displaced into the measuring cylinder.

Method 3:
If an irregular object floats in water, it will not completely displace its own volume of water. Hence, a sinker with a thread attached to it is first lowered into the measuring cylinder. The volume of the object and sinker is observed. The object to be measured is then tied to the sinker and lowered into the measuring cylinder until it is completely immersed in the water. The new reading is taken. The difference between the
two readings would give the volume of the object.

30
Q

definition of hardness?

A

resistance to wear and tear and scratches

ability to scratch another material

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