Density
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Density is defined as mass per unit volume. The SI unit for density is kg/m3, but g/cm3 is more commonly used. To calculate density, mass is measured using a scale and volume is measured using a ruler or graduated cylinder for irregular objects. Density can be used to differentiate between substances and is a characteristic property of matter. The density of a mixture is calculated by dividing the total mass of the mixture by the total volume.
Density
- 2. Density is defined as the mass in a unit of volume.
- 3. In the SI unit system, mass is measured in kg and volume is measured in m3, thus, the unit of density is kg/m3 (kilogram per cubic meter). But this is inconvenient for most substances, therefore, g/cm3 (gram per cubic centimeter) is a more common unit of density.
- 4. Densityis a characteristic property of matter. We can differentiate substances by using their densities.
- 7. In order to calculate the density of an object, first we measure its mass with a scale, then we find its volume by measuring it with a ruler, if it has a regular shape. Otherwise we use the graduated cylinder method for irregular objects, and liquids. Then, by dividing mass by volume, we find the density of the object.
- 8. What is the volume of 24 tons of cement? (dcement = 3000 kg/m3) Calculate the mass of copper having the same volume as 31,5 g of silver. Use Table 1.7.
- 9. A bottle has a mass of 70 g when it is empty, 90 g when it is full of water and 96 g when it is full of a liquid. What is the density of the liquid in g/cm3 and kg/m3 ?
- 10. Calculate the mass of air (at 0° C) in a room having dimensions of 3 m, 6 m, 5 m. See Table 1.7.
- 11. The density of a mixture is found by dividing the total mass of the mixture by its total volume.
- 13. 1.3 kg of a liquid and 2 kg of water are mixed in a container. Find the density of the mixture. Take dliquid = 1.3 g/cm3 and dwater = 1 g/cm3.
- 14. Two different substances of volumes 200 cm3 and 300 cm3 are mixed to make an alloy. If their densities are 1.2 g/cm3 and 1.6 g/cm3 respectively, find the density of the alloy.
- 15. One complete rotation of earth around its axis is called one day. It is equal to 24 hours (h), 1 hour is 60 minutes (min) and 1 minute is 60 seconds (s). The unit of time is the second. A stopwatch or clock is used to measure time.
- 16. What is the equivalent of one week in terms of hours, minutes and seconds?