# Get the Knowledge that sets you free...Science and Math for K8 to K12 students

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## Properties of Matter

Density, the property that makes you float If an object is less dense than the fluid in which it is placed, it will float. If it is more dense than the fluid, it will sink. Without swimming a person does sink in a pool since human body is denser than water. The Dead Sea, on the borders of Israel and Jordan, is the world's saltiest and densest body of water. Since human bodies have a lower density than the water of the Dead Sea, people can float in it effortlessly. The extremely salty water holds people up instead of letting them sink. The high salinity of the water provides swimmers with natural buoyancy without any efforts.

## After completing the topic, the student will be able to:

• Discuss the need of measurements in everyday life.
• Categorize the units used for scientific measurements into English System and Metric system.
• Distinguish fundamental unit and derived unit.
• Derive units for different physical quantities from fundamental units.
• Define the standard units of fundamental properties of matter such as mass, length etc.
• Give the mathematical and physical relationship between different physical quantities.
• Calculate the magnitude of one physical quantity from the magnitude of other given quantities.
Physical and chemical changes Liquid water and ice are both composed of water molecules. Melting the ice cube doesn't change the chemical composition of the molecules.
Measuring jar (cup) To transfer a desired volume of liquid, a measuring jar is used. As the composition of water is not effected during the process, volume is a physical property
Physical and chemical properties of matter

As we look at our surroundings, we observe a large variety of things with different shapes, sizes and textures. How can we distinguish or characterize those substances? Every substance has its own set of properties or characteristics that allow us to distinguish it from other substance. In chemistry we can view the substances on both the macroscopic level and the microscopic level. On macroscopic level we can directly observe the substance with our naked eye and we can feel it all over. But microscopic level is the level of small particles like atoms and molecules.

For example, at macroscopic level solids possesses definite shape and size but at microscopic level there is a regular frame work of atoms and molecules in a crystal lattice. We express the properties of matter in both of these levels. The important macroscopic properties of matter are length, area, mass, volume, weight and density. The important microscopic properties are mass, speed, kinetic energy of atoms or molecules that make up a substance.

These properties of substances are also classified into − physical properties and chemical properties. Physical properties are those properties which can be measured or observed without changing the identity or the composition of the substance. Some examples of physical properties are mass, volume, weight, density, color, odor, melting point, boiling point, density etc.

A chemical reaction should be carried out between the substances to measure or observe the chemical properties of a substance. Chemical properties are characteristic reactions of different substances which include acidity, basicity, combustibility etc.

Many physical properties of matter such as length, area, volume are quantitative in nature. A quantitative property can be measured and represented by a number, followed by units in which it is measured. For example, volume of a liquid can be represented as 5l. Here 5 is the number and ' l 'denotes litre – the unit in which the volume is measured.

Building a house need measurements The weight of the cement required is estimated and measured. The length and quantity of iron bars and bricks are fixed. The sizes of tables which are made with wood are measured. All these measurements require standard units.
Units of measurement

As we already stated, quantitative properties of matter are associated with numbers. When a number represents a measured quantity, the units of that quantity must always be specified. Almost everything that we own − house, food, vehicle, clothes, etc are manufactured with certain measured parts of matter.

For example, building a house needs raw materials like cement, bricks, iron, wood etc. The weight of the cement required is estimated and measured. The length and cross section of iron bars and quantity of bricks are fixed. The sizes of tables which are made of wood are measured. All these measurements require standard units. In chemistry a large number of chemical reactions are carried out in the laboratory. A chemist should know about the exact amount of chemicals required to carry out the reaction to minimize the wastage and obtain the maximum yield.

The units used for scientific measurements are categorized into following two different systems of measurement, the English System and the Metric System. The Metric system which was first developed in France in late eighteenth century, was more convenient as it was based on the decimal system.

The United States has traditionally used English system. In order to resolve the ambiguity, the scientist community felt that there was a need of a common standard system. In 1960, an international agreement was reached specifying a particular choice of metric units for use in scientific measurements throughout the world. This was called SIunits.