THE SCIENCES OF PHYSICS AND CHEMISTRY Science aims to provide a rational explanation for what occurs. It is divided into branches, such as physics, chemistr y and biology, which study dif ferent types of situations. REVIEW 1 Explain whether these phenomena are physical or chemical changes: a) Dissolving sugar in water. b) Burning wood. c) Grinding food. d) Moulding a piece of clay. e) Melting ice cream. f ) Frying a steak. A C T I V I T I E S Physics explains the properties of water, such as its temperature, density and physical state. When water cools down , it turns into ice. When water heats up, it turns into steam. Ice, steam and water are the same substance in different physical states. Chemistr y studies which elements make up water and how they are held together. When we pass an electric current through water, two gases, hydrogen, H2, and oxygen, O2, appear in the tubes. These substances are different from water, H2O. Examples of physical changes Examples of chemical changes Changes in shape or position Mixtures Combustion Oxidation Hydrogen Oxygen Physics studies the changes in matter that do not affect its nature. After a physical change, substances remain the same. Chemistr y studies the composition of matter and the changes that affect its nature. After a chemical change, substances are transformed into different substances. Physics Chemistr y 10
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