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Materials Around Us - How Heavy or Light?

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Mass (mm) is the measure of the amount of matter present in an object. It is usually measured in grams (gg) or kilograms (kgkg).

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Volume (VV) is the total space occupied by an object. Common units include cubic centimeters (cm3cm^3) and cubic meters (m3m^3).

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Density (ρ\rho) describes how heavy an object is for its size. It is the mass per unit volume of a substance.

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Objects with a density lower than the density of water (1 g/cm31 \text{ g/cm}^3) will float on water.

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Objects with a density higher than the density of water will sink in water.

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Relative heaviness can be compared by taking equal volumes of different materials and measuring their masses.

📐Formulae

Density=MassVolume\text{Density} = \frac{\text{Mass}}{\text{Volume}}

ρ=mV\rho = \frac{m}{V}

Mass=Density×Volume\text{Mass} = \text{Density} \times \text{Volume}

Volume=MassDensity\text{Volume} = \frac{\text{Mass}}{\text{Density}}

💡Examples

Problem 1:

An iron cube has a mass of 156 g156 \text{ g} and a volume of 20 cm320 \text{ cm}^3. Calculate its density.

Solution:

Density=15620=7.8 g/cm3\text{Density} = \frac{156}{20} = 7.8 \text{ g/cm}^3

Explanation:

By dividing the total mass (156 g156 \text{ g}) by the total volume (20 cm320 \text{ cm}^3), we find that every cubic centimeter of iron weighs 7.8 g7.8 \text{ g}.

Problem 2:

A piece of wood has a mass of 40 g40 \text{ g} and a volume of 50 cm350 \text{ cm}^3. Will it sink or float in water? (Density of water = 1 g/cm31 \text{ g/cm}^3)

Solution:

Density of wood=4050=0.8 g/cm3\text{Density of wood} = \frac{40}{50} = 0.8 \text{ g/cm}^3

Explanation:

Since 0.8 g/cm3<1 g/cm30.8 \text{ g/cm}^3 < 1 \text{ g/cm}^3, the density of the wood is less than the density of water, so it will float.

Problem 3:

A student measures the mass of a bottle filled with sand as 850 g850 \text{ g}. If the empty bottle weighs 125 g125 \text{ g}, what is the mass of the sand alone?

Solution:

850−125725\begin{array}{r} 850 \\ -125 \\ \hline 725 \end{array} The mass of the sand is 725 g725 \text{ g}.

Explanation:

To find the mass of the contents, subtract the mass of the container (empty bottle) from the total mass (bottle + sand).