This chapter looks at key ideas and activities that can be used to help students learn about solids, liquids and gases, and understand that some materials change state when they are heated or cooled. Find out how to teach science curriculum topics through engaging sustainability contexts.
Our topic webs include suggestions for classroom activities that develop numeracy, literacy and scientific skills. Connect your curriculum teaching on chemical changes to engaging sustainability contexts. This topic web suggests classroom activities linked to plastic degradation and clean cooking.
Connect your curriculum teaching on electricity to engaging sustainability contexts. This topic web suggests classroom activities linked to batteries and electric cars. Site powered by Webvision Cloud. Primary science. No comments. If you teach primary science, see the headings below to find out how to use this resource: Skill development Children will develop their working scientifically skills by: Asking their own questions about scientific phenomena. Selecting and planning the most appropriate ways to answer questions, including: Researching using a wide range of secondary sources of information.
Grouping and classifying. Similarly, if you have a piece of paper, you don't change it into something other than a piece of paper by ripping it up. What was paper before you started tearing is still paper when you are done. Again, this is an example of a physical change. Physical changes can further be classified as reversible or irreversible. The melted ice cube may be refrozen, so melting is a reversible physical change.
Physical changes that involve a change of state are all reversible. Other changes of state include vaporization liquid to gas , freezing liquid to solid , and condensation gas to liquid.
Dissolving is also a reversible physical change. When salt is dissolved into water, the salt is said to have entered the aqueous state. The salt may be regained by boiling off the water, leaving the salt behind. This means that one substance with a certain set of properties such as melting point, color, taste, etc is turned into a different substance with different properties.
Chemical changes are frequently harder to reverse than physical changes. One good example of a chemical change is burning a candle. The act of burning paper actually results in the formation of new chemicals carbon dioxide and water from the burning of the wax. Another example of a chemical change is what occurs when natural gas is burned in your furnace. In this case, not only has the appearance changed, but the structure of the molecules has also changed.
The new substances do not have the same chemical properties as the original ones. Therefore, this is a chemical change. We can't actually see molecules breaking and forming bonds, although that's what defines chemical changes.
We have to make other observations to indicate that a chemical change has happened. Some of the evidence for chemical change will involve the energy changes that occur in chemical changes, but some evidence involves the fact that new substances with different properties are formed in a chemical change.
Label each of the following changes as a physical or chemical change. Give evidence to support your answer. Homogeneous mixtures solutions can be separated into their component substances by physical processes that rely on differences in some physical property, such as differences in their boiling points.
What Is a Physical Change? In a physical change, the material involved in the change is structurally the same before and after the change. Types of some physical changes are texture, shape, temperature, and a change in the state of matter. A change in the texture of a substance is a change in the way it feels. For instance, a block of wood may feel rough when you run your finger across it but rubbing the wood with sandpaper smooths the surface so it no longer feels rough.
The wood itself has not changed during sanding to become a new material, only the texture of the surface changed. A piece of metal may be heated in a fire until it glows, but the metal is the same material before heating and after cooling.
Similarly, when a material changes phase, it only changes physically; the substance is still the same. Think about ice melting into water, and then water being heated up and turning into steam. The chemical structure of water is the same whether it is a solid ice , liquid, or gas steam.
What Is a Chemical Change? A chemical change occurs when the composition of a substance is changed, which requires the breaking and forming of chemical bonds during a chemical reaction. This results in the rearranging of atoms in substances to form the products of a chemical reaction, which are brand new molecules that cannot be easily reverted back to their original state. Sometimes it is difficult to tell if a chemical reaction has taken place. To help determine whether there has been a reaction, chemists consider the basic indicators that a reaction has occurred, such as a change in temperature, a change in color, the development of an odor, the formation of a precipitate , or the formation of a gas.
In a chemical alteration, the temperature change occurs as a result of the breaking or formation of chemical bonds. When the chemical bonds of the reactants are broken, sometimes excess energy is released, causing heat to be discharged, and leading to an increase in temperature. Alternatively, a reaction may require energy from the environment in order to take place, causing heat to be absorbed, and leading to a decrease in temperature.
Burning wood is an example of a reaction that releases excess energy as heat. A chemical cold pack in a first aid kit is an example of a chemical reaction that absorbs heat energy resulting in cooling. An example of a color change signaling a chemical reaction can be observed when iron reacts with oxygen to produce iron oxide, such as when an iron nail is left outside, and it develops a reddish-brown rust.
The melted ice cube may be refrozen, so melting is a reversible physical change. Physical changes that involve a change of state are all reversible.
Other changes of state include vaporization liquid to gas , freezing liquid to solid , and condensation gas to liquid. Dissolving is also a reversible physical change. When salt is dissolved into water, the salt is said to have entered the aqueous state. The salt may be regained by boiling off the water, leaving the salt behind. This means that one substance with a certain set of properties such as melting point, color, taste, etc is turned into a different substance with different properties.
Chemical changes are frequently harder to reverse than physical changes. One good example of a chemical change is burning a candle.
The act of burning paper actually results in the formation of new chemicals carbon dioxide and water from the burning of the wax. Another example of a chemical change is what occurs when natural gas is burned in your furnace. In this case, not only has the appearance changed, but the structure of the molecules has also changed. The new substances do not have the same chemical properties as the original ones. Therefore, this is a chemical change. We can't actually see molecules breaking and forming bonds, although that's what defines chemical changes.
We have to make other observations to indicate that a chemical change has happened. Some of the evidence for chemical change will involve the energy changes that occur in chemical changes, but some evidence involves the fact that new substances with different properties are formed in a chemical change. Label each of the following changes as a physical or chemical change. Give evidence to support your answer. Homogeneous mixtures solutions can be separated into their component substances by physical processes that rely on differences in some physical property, such as differences in their boiling points.
Two of these separation methods are distillation and crystallization. Distillation makes use of differences in volatility, a measure of how easily a substance is converted to a gas at a given temperature. A simple distillation apparatus for separating a mixture of substances, at least one of which is a liquid.
The most volatile component boils first and is condensed back to a liquid in the water-cooled condenser, from which it flows into the receiving flask.
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