### Physics Specific Gravity

##### Specific Gravity

Specific gravity is a measure of the density of a substance relative to the density of water. It is defined as the ratio of the density of a substance to the density of water at 4°C. The specific gravity of a substance is dimensionless and is often expressed as a number without units.

##### Calculating Specific Gravity

The specific gravity of a substance can be calculated by dividing the density of the substance by the density of water at 4°C. The density of a substance can be measured using a variety of methods, including the following:

**Mass/volume method:**This method involves measuring the mass of a known volume of the substance. The density is then calculated by dividing the mass by the volume.**Hydrometer method:**This method involves using a hydrometer, which is a floating device that measures the specific gravity of a liquid. The hydrometer is placed in the liquid, and the specific gravity is read from the scale on the hydrometer.**Pycnometer method:**This method involves using a pycnometer, which is a specialized container that is used to measure the density of a liquid. The pycnometer is filled with the liquid, and the mass of the pycnometer and the liquid is measured. The density is then calculated by dividing the mass of the liquid by the volume of the pycnometer.

##### Applications of Specific Gravity

Specific gravity is used in a variety of applications, including the following:

**Determining the purity of a substance:**The specific gravity of a substance can be used to determine its purity. For example, the specific gravity of gold is 19.3 g/cm³. If a sample of gold has a specific gravity of less than 19.3 g/cm³, it is not pure gold.**Measuring the concentration of a solution:**The specific gravity of a solution can be used to measure its concentration. For example, the specific gravity of a sugar solution increases as the concentration of sugar in the solution increases.**Identifying minerals:**The specific gravity of a mineral can be used to help identify it. For example, the specific gravity of pyrite is 5.0 g/cm³, while the specific gravity of quartz is 2.65 g/cm³.

Specific gravity is a useful measure of the density of a substance. It is used in a variety of applications, including determining the purity of a substance, measuring the concentration of a solution, and identifying minerals.

##### Specific Gravity Formula

The specific gravity of a substance is defined as the ratio of its density to the density of water at 4°C. It is a dimensionless quantity and is often expressed as a number without units.

##### Formula

The specific gravity of a substance can be calculated using the following formula:

$ Specific\ Gravity = Density\ of\ Substance / Density\ of\ Water\ at\ 4°C $

where:

- Specific Gravity is the dimensionless quantity representing the relative density of a substance compared to water
- Density of Substance is the mass of the substance per unit volume, typically expressed in grams per cubic centimeter (g/cm³)
- Density of Water at 4°C is the standard density of water at 4°C, which is approximately 1 g/cm³

##### Example

For example, the specific gravity of gold is 19.3, which means that gold is 19.3 times denser than water at 4°C.

The specific gravity formula provides a simple and convenient way to compare the density of a substance to the density of water. It is a useful property that has numerous applications in science, engineering, and everyday life.

**List of Materials and their Specific Gravity**

Specific gravity is a measure of the density of a material relative to the density of water. It is defined as the ratio of the density of a material to the density of water at 4°C. The specific gravity of a material is a dimensionless quantity.

The following table lists the specific gravity of some common materials:

Material | Specific Gravity |
---|---|

Aluminum | 2.7 |

Brass | 8.5 |

Concrete | 2.4 |

Copper | 8.9 |

Glass | 2.5 |

Gold | 19.3 |

Iron | 7.8 |

Lead | 11.3 |

Mercury | 13.6 |

Nickel | 8.9 |

Platinum | 21.4 |

Silver | 10.5 |

Steel | 7.8 |

Tin | 7.3 |

Titanium | 4.5 |

Wood (oak) | 0.6 |

Water | 1.0 |

**Specific Gravity of Liquids**

The specific gravity of a liquid is the ratio of the density of the liquid to the density of water at 4°C. The specific gravity of a liquid is a dimensionless quantity.

The following table lists the specific gravity of some common liquids:

Liquid | Specific Gravity |
---|---|

Acetone | 0.79 |

Alcohol (ethyl) | 0.79 |

Benzene | 0.88 |

Carbon tetrachloride | 1.59 |

Gasoline | 0.70 |

Glycerin | 1.26 |

Mercury | 13.6 |

Milk | 1.03 |

Olive oil | 0.92 |

Seawater | 1.02 |

Sulfuric acid | 1.84 |

Water | 1.0 |

**Specific Gravity of Gases**

The specific gravity of a gas is the ratio of the density of the gas to the density of air at 0°C and 1 atm. The specific gravity of a gas is a dimensionless quantity.

The following table lists the specific gravity of some common gases:

Gas | Specific Gravity |
---|---|

Air | 1.00 |

Carbon dioxide | 1.53 |

Helium | 0.14 |

Hydrogen | 0.07 |

Methane | 0.55 |

Nitrogen | 0.97 |

Oxygen | 1.10 |

Propane | 1.56 |

Sulfur dioxide | 2.26 |

**Applications of Specific Gravity**

Specific gravity is used in a variety of applications, including:

**Determining the density of a material.**The specific gravity of a material can be used to calculate its density by multiplying the specific gravity by the density of water.**Comparing the densities of different materials.**The specific gravity of different materials can be compared to determine which material is denser.**Identifying materials.**The specific gravity of a material can be used to identify the material.**Designing and engineering structures.**The specific gravity of materials is used in the design and engineering of structures to ensure that the structures are strong enough to withstand the loads that they will be subjected to.

Specific gravity is a useful property that can be used for a variety of purposes. It is a simple and inexpensive measurement that can provide valuable information about the density and composition of materials.

**Difference between Density and Specific Gravity**

**Density**

- Density is a measure of how much mass is packed into a given volume of a substance.
- It is defined as the mass per unit volume.
- The SI unit of density is kilograms per cubic meter (kg/m³).
- Density is an intrinsic property of a substance, meaning that it does not depend on the amount of the substance or the shape of the object.
- Density can be used to compare the masses of different substances with the same volume.

**Specific Gravity**

- Specific gravity is a measure of how dense a substance is compared to water.
- It is defined as the ratio of the density of a substance to the density of water at 4°C.
- The specific gravity of a substance is dimensionless.
- Specific gravity is often used to compare the densities of liquids and solids.

**Comparison of Density and Specific Gravity**

Property | Density | Specific Gravity |
---|---|---|

Definition | Mass per unit volume | Ratio of density to density of water at 4°C |

Units | kg/m³ | Dimensionless |

Dependence on amount of substance | No | No |

Dependence on shape of object | No | No |

Use | Comparing masses of different substances with same volume | Comparing densities of liquids and solids |

**Example**

The density of gold is 19.3 g/cm³. The specific gravity of gold is 19.3. This means that gold is 19.3 times denser than water.

**Conclusion**

Density and specific gravity are both measures of how dense a substance is. However, density is an intrinsic property of a substance, while specific gravity is a comparison of the density of a substance to the density of water.